The
effects of cannabis have both psychological and physiological effects on the human body. The effects of cannabis are mediated through
cannabinoidsCannabinoids are a group of terpenophenolic compounds present in Cannabis and which occur naturally in the nervous and immune systems of animals. The broader definition of cannabinoids refers to a group of substances that are structurally related to tetrahydrocannabinol or that bind to...
, most notably
tetrahydrocannabinolTetrahydrocannabinol , also known as delta-9-tetrahydrocannabinol , Δ
1-THC , or dronabinol, is the main psychoactive substance found in the Cannabis plant....
(THC). Five
EuropeanEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
countries and thirteen US states have legalized
medical cannabisMedical cannabis refers to the use of the dried flowers and subtending leafs and stems from pistillate Cannabis plants as a physician-recommended drug or herbal therapy....
if prescribed for
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
,
painPhysical Pain is the unpleasant feeling common to a headache and a stubbed toe. It typically consists of negative affect and aversion, and has location, duration, intensity and a distinctive quality...
, and alleviation of symptoms surrounding chronic illness, although it remains banned under US federal law.
AcuteAcute toxicity describes the adverse effects of a substance which result either from a single exposure or from multiple exposures in a short space of time...
effects while under the influence can include
euphoriaEuphoria is an emotional and mental state defined as a sense of great elation and well being.Euphoria or euphoric may also refer to:* Euphoria , genus of scarab beetles...
,
anxietyAnxiety is a psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create an unpleasant feeling that is typically associated with uneasiness, fear, or worry....
, temporary
short-term memoryShort-term memory refers to the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory is believed to be in the order of seconds...
loss, and circulation effects which may increase risks of heart attacks and
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
s. However,
chronicChronic toxicity is a property of a substance that has toxic effects on a living organism, when that organism is exposed to the substance continuously or repeatedly. Compared with acute toxicity.Two distinct situations need to be considered:...
use is not associated with some cardiovascular risk factors such as blood
triglycerideis a glyceride in which the glycerol is esterified with three fatty acids. It is the main constituent of vegetable oil and animal fats.- Chemical structure :...
levels and blood pressure, as indicated in a longitudinal study. The evidence of long-term effects on memory is preliminary and hindered by confounding factors. Concerns have been raised about the potential for long-term cannabis consumption to increase risk for
schizophreniaSchizophrenia , from the Greek roots skhizein and phrēn, phren- is a psychiatric diagnosis that describes a mental disorder characterized by abnormalities in the perception or expression of reality...
, bipolar disorders, and major depression, but the ultimate conclusions on these factors are disputed.
Biochemical effects
The most prevalent group of psychoactive substances in cannabis is
cannabinoidsCannabinoids are a group of terpenophenolic compounds present in Cannabis and which occur naturally in the nervous and immune systems of animals. The broader definition of cannabinoids refers to a group of substances that are structurally related to tetrahydrocannabinol or that bind to...
, including delta-9-
tetrahydrocannabinolTetrahydrocannabinol , also known as delta-9-tetrahydrocannabinol , Δ
1-THC , or dronabinol, is the main psychoactive substance found in the Cannabis plant....
(Δ
9-THC, commonly called simply THC). In the past two decades, the average content of THC in marijuana sold in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
has increased from about 1% to 3–4% or more.
Some varieties, having undergone careful selection and growing techniques, can yield as much as 29% THC. Another psychoactive cannabinoid present in
Cannabis sativa is
tetrahydrocannabivarinTetrahydrocannabivarin , also known as tetrahydrocannabivarol, is a psychoactive cannabinoid found naturally in Cannabis sativa. It is an analogue of tetrahydrocannabinol with the sidechain shortened by two CH
2 groups...
(THCV), but it is only found in small amounts.
In addition, there are also similar compounds contained in cannabis that do not exhibit any psychoactive response but are obligatory for functionality:
cannabidiolCannabidiol is a psychoactive cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.CBD alone is not intoxicating, but displayed sedative effects in animal tests...
(CBD), an
isomerIn chemistry, isomers are compounds with the same molecular formula but different structural formulas. The word is derived from the Greek ισομερης, isomerès; isos = "equal", méros = "part"....
of THC;
cannabinolCannabinol is a non-psychoactive cannabinoid found in Cannabis sativa and Cannabis indica. It is also a metabolite of tetrahydrocannabinol . CBN acts as an agonist at the CB
1 and CB
2 receptors, but with lower affinity in comparison to THC.- External links :* Compounds found...
(CBN), an oxidation product of THC;
cannabivarinCannabivarin, also known as cannabivarol or CBV, is a non-psychoactive cannabinoid found in minor amounts in the hemp plant Cannabis sativa. It is an analog of cannabinol with the sidechain shortened by two CH
2 groups. CBV is an oxidation product of tetrahydrocannabivarin .- External...
(CBV), an
analogIn chemistry, structural analogs , also known as chemical analogs or simply analogs, are compounds in which one or more atoms, functional groups, or substructures have been replaced with different atoms, groups, or substructures...
of CBN with a different sidechain,
cannabidivarinCannabidivarine , also known as cannabidivarol, is a non-psychoactive cannabinoid found in low amounts in Cannabis sativa. It is an analog of cannabidiol , with the side-chain shortened by two CH
2 groups...
(CBDV), an analog of CBD with a different side chain, and cannabinolic acid. How these other compounds interact with THC is not fully understood. Some clinical studies have proposed that CBD acts as a balancing force to regulate the strength of the psychoactive agent THC. Marijuana with relatively high ratios of THC:CBD is less likely to induce
anxietyAnxiety is a psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create an unpleasant feeling that is typically associated with uneasiness, fear, or worry....
than marijuana with low THC:CBD ratios. CBD is also believed to regulate the body’s metabolism of THC by inactivating cytochrome P450, an important class of enzymes that metabolize drugs. Experiments in which mice were treated with CBD followed by THC showed that CBD treatment was associated with a substantial increase in brain concentrations of THC and its major metabolites, most likely because it decreased the rate of clearance of THC from the body. Cannabis cofactor compounds have also been linked to lowering body temperature, modulating immune functioning, and cell protection. The
essential oilAn essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile or ethereal oils, or simply as the "oil of" the plant from which they were extracted, such as oil of clove. An oil is "essential" in the sense that it...
of cannabis contains many fragrant
terpenoidThe terpenoids , sometimes called isoprenoids, are a large and diverse class of naturally-occurring organic chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways. Most are multicyclic structures that differ from one another not only in...
s which may synergize with the cannabinoids to produce their unique effects. THC is converted rapidly to
11-hydroxy-THC11-Hydroxy-Δ
9-tetrahydrocannabinol, abbreviated as 11-OH-THC, is the main active metabolite of THC which is formed in the body after cannabis consumption. 11-Hydroxy-THC has been shown to be active in its own right, but the effects produced are not necessarily identical to those of THC...
, which is also pharmacologically active, so the drug effect outlasts measurable THC levels in blood.
THC and cannabidiol are also neuroprotective
antioxidantAn antioxidant is a molecule capable of slowing or preventing the oxidation of other molecules. Oxidation is a chemical reaction that transfers electrons from a substance to an oxidizing agent. Oxidation reactions can produce free radicals, which start chain reactions that damage cells...
s. Research in rats has indicated that THC prevented hydroperoxide-induced oxidative damage as well as or better than other antioxidants in a chemical (Fenton reaction) system and
neuronA neuron is an excitable cell in the nervous system that processes and transmits information by electrochemical signaling. Neurons are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves...
al cultures. Cannabidiol was significantly more protective than either
vitamin EVitamin E is a generic term for tocopherols and tocotrienols. Vitamin E is a family of α-, β-, γ-, and δ-tocopherols and corresponding four tocotrienols. Vitamin E is a fat-soluble antioxidant that stops the production of reactive oxygen species formed when fat undergoes oxidation...
or
vitamin CVitamin C or L-ascorbic acid is an essential nutrient for humans, in which it functions as a vitamin. Ascorbate is required for a range of essential metabolic reactions in all animals and plants...
.
In 1990, the discovery of
cannabinoid receptorThe cannabinoid receptors are a class of cell membrane receptors under the G-protein coupled receptor superfamily. Cannabinoid receptors are activated by ligands, which are lipid compounds known collectively as cannabinoids...
s located throughout the
brainThe brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all...
and body, along with
endogenousThe word endogenous means "proceeding from within", the opposite of exogenous.-Biology:Endogenous substances are those that originate from within an organism, tissue, or cell . Endogenous retrovirus are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
cannabinoid neurotransmitters like
anandamideAnandamide, also known as N-arachidonoylethanolamine or AEA, is an endogenous cannabinoid neurotransmitter found in animal and human organs, especially in the brain...
(a
lipidLipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, phospholipids, and others...
material derived
ligandIn chemistry, a ligand is either an atom, ion, or molecule that binds to a central metal-atom to produce a coordination complex. The bonding between the metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The metal-ligand bonding ranges from covalent...
from
arachidonic acidArachidonic acid is an omega-6 fatty acid 20:4.It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA, sometimes ARA) is an omega-6 fatty acid 20:4(ω-6).It is the counterpart to the saturated arachidic acid found in peanut oil, Arachidonic acid (AA,...
), suggested that the use of cannabis affects the brain in the same manner as a naturally occurring brain chemical. Cannabinoids usually contain a 1,1'-di-methyl-pyrane ring, a variedly derivatized aromatic ring and a variedly
unsaturatedIn chemistry, saturation has five different meanings:#In physical chemistry, saturation is the point at which a solution of a substance can dissolve no more of that substance and additional amounts of it will appear as a precipitate...
cyclohexylCyclohexane is a cycloalkane with the molecular formula C
6H
12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which are intermediates used in the production...
ring and their immediate chemical precursors, constituting a family of about 60 bi-cyclic and tri-cyclic compounds. Like most other neurological processes, the effects of cannabis on the brain follow the standard protocol of
signal transductionIn biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another. Most processes of signal transduction involve ordered sequences of biochemical reactions inside the cell, which are carried out by enzymes and activated by second messengers,...
, the electrochemical system of sending signals through neurons for a biological response. It is now understood that cannabinoid receptors appear in similar forms in most vertebrates and invertebrates and have a long
evolutionary historyEvolutionary biology is a sub-field of biology concerned with the origin of species from a common descent and descent of species, as well as their change, multiplication and diversity over time. Someone who studies evolutionary biology is known as an evolutionary biologist...
of 500 million years. Cannabinoid receptors decrease adenylyl cyclase activity, inhibit
calcium N channelsIon channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of all living cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
, and disinhibit
K+A channelsIn the field of cell biology, potassium channels are the most widely distributed type of ion channel and are found in virtually all living organisms. They form potassium-selective pores that span cell membranes...
. There are two types of cannabinoid receptors (CB1 and CB2).
The CB1 receptor is found primarily in the brain and mediates the psychological effects of THC. The CB2 receptor is most abundantly found on cells of the
immune systemAn immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumour cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. Cannabinoids act as immunomodulators at CB2 receptors, meaning they increase some immune responses and decrease others. For example, nonpsychotropic cannabinoids can be used as a very effective
anti-inflammatoryAnti-inflammatory refers to the property of a substance or treatment that reduces inflammation. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids which affect the brain.-Medications:...
. The affinity of cannabinoids to bind to either receptor is about the same, with only a slight increase observed with the plant-derived compound CBD binding to CB2 receptors more frequently. Cannabinoids likely have a role in the brain’s control of movement and
memoryIn psychology, memory is an organism's mental ability to store, retain, and recall information. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing the memory....
, as well as natural pain modulation. It is clear that cannabinoids can affect pain transmission and, specifically, that cannabinoids interact with the brain's endogenous
opioidAn opioid is a chemical that works by binding to opioid receptors, which are found principally in the central nervous system and the gastrointestinal tract...
system and may affect dopamine transmission. This is an important physiological pathway for the medical treatment of pain.
The cannabinoid receptor is a typical member of the largest known family of receptors called a
G protein-coupled receptorG protein-coupled receptors , also known as seven-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptor, and G protein-linked receptors , comprise a large protein family of transmembrane receptors that sense molecules outside the cell and activate inside signal...
. A signature of this type of receptor is the distinct pattern of how the receptor molecule spans the
cell membraneThe cell membrane is the biological membrane separating the interior of a cell from the outside environment....
seven times. The location of cannabinoid receptors exists on the cell membrane, and both outside (
extracellularIn cell biology, molecular biology and related fields, the word extracellular means "outside the cell". This space is usually taken to be outside the plasma membranes, and occupied by fluid...
ly) and inside (
intracellularNot to be confused with intercellular, meaning "between cells".In cell biology, molecular biology and related fields, the word intracellular means "inside the cell".It is used in contrast to extracellular...
ly) the cell membrane. CB1 receptors, the bigger of the two, are extraordinarily abundant in the brain: 10 times more plentiful than μ-
opioid receptorOpioid receptors are a group of G-protein coupled receptors with opioids as ligands. The endogenous opioids are dynorphins, enkephalins, endorphins, endomorphins and nociceptin...
s, the receptors responsible for the effects of
morphineMorphine is a highly potent opiate analgesic psychoactive drug, is the principal active ingredient in Papaver somniferum , is considered to be the prototypical opioid. Like other opioids, e.g...
. CB2 receptors are structurally different (the
homologyIn evolutionary biology, homology refers to any similarity between characteristics of organisms that is due to their shared ancestry. The word homologous derives from the ancient Greek ομολογειν, 'to agree'. There are examples in different branches of biology...
between the two subtypes of receptors is 44%), found only on cells of the immune system, and seems to function similarly to its CB1 counterpart. CB2 receptors are most commonly prevalent on B-cells, natural killer cells, and monocytes, but can also be found on polymorphonuclear neutrophil cells,
T8 cellsA cytotoxic T cell belongs to a sub-group of T lymphocytes that are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses , or are otherwise damaged or dysfunctional...
, and
T4 cellsT helper cells are a sub-group of lymphocytes that play an important role in establishing and maximizing the capabilities of the immune system...
. In the tonsils the CB2 receptors appear to be restricted to B-lymphocyte-enriched areas.
THC and endogenous anandamide additionally interact with
glycine receptorThe glycine receptor, or GlyR, is the receptor for the amino acid neurotransmitter glycine. It is one of the most widely distributed inhibitory receptors in the central nervous system and has important roles in a variety of physiological processes, especially in mediating inhibitory...
s.
Sustainability in the body
Most
cannabinoidsCannabinoids are a group of terpenophenolic compounds present in Cannabis and which occur naturally in the nervous and immune systems of animals. The broader definition of cannabinoids refers to a group of substances that are structurally related to tetrahydrocannabinol or that bind to...
are
lipophilicLipophilicity, , refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. These non-polar solvents are themselves lipophilic — the axiom that like dissolves like generally holds true...
(fat soluble) compounds that easily store in fat, thus yielding a long elimination half-life relative to other
recreational drugRecreational drug use is the use of psychoactive drugs for recreational purposes rather than for work, approved medical or spiritual purposes, although the distinction is not always clear ....
s. The THC molecule, and related compounds, are usually detectable in drug tests from 3 days up to 10 days according to Redwood Laboratories, after using cannabis depending on frequency of use (see
drug testA drug test is a technical analysis of a biological specimen - urine, hair, blood, sweat, or oral fluid / saliva - to determine the presence or absence of specified parent drugs or their metabolites....
). This detection is possible because non-psychoactive THC metabolites are stored for long periods of time in fat cells, and THC has an extremely low water solubility. The rate of elimination of metabolites is slightly greater for more frequent users due to tolerance.
Toxicity
THC has an extremely low
toxicityToxicity is the degree to which a substance is able to damage an exposed organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a substructure of the organism, such as a cell or an organ , such as the liver...
and the amount that can enter the body through the consumption of cannabis plants poses no threat of death. In lab animal tests, scientists have had much difficulty administering a dosage of THC that is high enough to be lethal. It also appears that humans cannot die from ingesting too much THC, unless it were introduced into the body
intravenouslyIntravenous therapy or IV therapy is the giving of liquid substances directly into a vein. It can be intermittent or continuous; continuous administration is called an intravenous drip. The word intravenous simply means "within a vein", but is most commonly used to refer to IV therapy...
(See also:
Intravenous Marijuana SyndromeIntravenous Marijuana Syndrome is a rare distinct short-term clinical syndrome related to the IV injection of boiled cannabis broth, which had been filtered through a cotton cloth. The syndrome has at least 25 known cases in the English language literature, all prior to 1983...
). Indeed, a 1988 ruling from the United States Department of Justice concluded that "In practical terms, marijuana cannot induce a lethal response as a result of drug-related toxicity."
According to the
Merck IndexThe Merck Index is an encyclopedia of chemicals, drugs and biologicals with over 10,000 monographs on single substances or groups of related compounds. It also includes an appendix with monographs on organic name reactions. It is published by the United States pharmaceutical company Merck & Co...
, the
LD50In toxicology, the median lethal dose, LD50 , LC50 or LCt50 of a toxic substance or radiation is the dose required to kill half the members of a tested population...
of THC (the dose which causes the death of 50% of individuals) is 1270 mg/kg for male rats and 730 mg/kg for female rats from oral assumption in sesame oil, and 42 mg/kg for rats from inhalation.
The ratio of cannabis material required to produce a fatal overdose to the amount required to saturate cannabinoid receptors and cause intoxication is 40,000:1; consumption of such a large dose is virtually impossible. There had been no reported deaths or permanent injuries sustained as a result of a marijuana overdose. However in 2009 it was reported in the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
that a man died from the acute affects of cannabis "possibly experiencing one of the toxic effects of cannabis - a fast heart rate and hyperventilating - [which] can lead to heart failure". The coroner recorded a verdict of "death due to misuse of drugs". It is not known if the man had any underlying medical condition. It is generally considered impossible to overdose on marijuana, as the user would certainly either fall asleep or otherwise become incapacitated from the effects of the drug before being able to consume enough THC to be mortally toxic. According to a 2006
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
government report, using cannabis is much less dangerous than tobacco, prescription drugs, and alcohol in social harms, physical harm, and addiction. It was found in 2007 that while tobacco and cannabis smoke are quite similar, cannabis smoke contained higher amounts of
ammoniaAmmonia is a compound of nitrogen and hydrogen with the formula NH
3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers...
,
hydrogen cyanideHydrogen cyanide is a chemical compound with chemical formula HCN. A solution of hydrogen cyanide in water is called hydrocyanic acid. Hydrogen cyanide is a colorless, extremely poisonous, and highly volatile liquid that boils slightly above room temperature at 26 °C...
, and nitrogen oxides, but lower levels of carcinogenic
polycyclic aromatic hydrocarbonPolycyclic aromatic hydrocarbons are chemical compounds that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning...
s (PAHs). This study found that directly inhaled cannabis smoke contained 20 times as much ammonia and 5 times as much hydrogen cyanide as tobacco smoke and compared the properties of both mainstream and sidestream (smoke emitted from a smouldering 'joint' or 'cone') smoke. Sidestream cannabis smoke was found to contain higher concentrations of selected polycyclic aromatic hydrocarbons (PAHs) than sidestream tobacco smoke.
Psychoactive effects
The psychoactive effects of cannabis, known as a "high", are subjective and can vary based on the individual and the method of use. Some effects may include an
altered state of consciousnessAn altered state of consciousness, , also named altered state of mind is any condition which is significantly different from a normal waking beta wave state. The expression was used as early as 1969 by Charles Tart and describes induced changes in one's mental state, almost always temporary...
,
euphoriaEuphoria is an emotional and mental state defined as a sense of great elation and well being.Euphoria or euphoric may also refer to:* Euphoria , genus of scarab beetles...
, feelings of well-being, relaxation or stress reduction, increased appreciation of humor, music or art, joviality,
metacognitionMetacognition is defined as "cognition about cognition", or "knowing about knowing." It can take many forms; "it includes knowledge about when and where to use particular strategies for learning or for problem solving." "Metamemory, individuals' knowledge about memory, is an especially important...
and
introspectionIntrospection is the self-observation and reporting of conscious inner thoughts, desires and sensations. It is a conscious mental and usually purposive process relying on thinking, reasoning, and examining one's own thoughts, feelings, and, in more spiritual cases, one's soul...
, enhanced recollection (
episodic memoryEpisodic memory is the memory of autobiographical events that can be explicitly stated. Semantic and episodic memory together make up the category of declarative memory, which is one of the two major divisions in memory...
), increased sensuality, increased awareness of sensation, increased
libidoLibido in its common usage means sexual desire; however, more technical definitions, such as those found in the work of Carl Jung, are more general, referring to libido as the free creative—or psychic—energy an individual has to put toward personal development or individuation.- History of the...
, creative or philosophical thinking, disruption of linear memory and
paranoiaParanoia is a thought process heavily influenced by excessive anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs concerning a perceived threat towards oneself. In the original Greek, παράνοια simply means madness...
or
anxietyAnxiety is a psychological and physiological state characterized by cognitive, somatic, emotional, and behavioral components. These components combine to create an unpleasant feeling that is typically associated with uneasiness, fear, or worry....
.
Cannabis also produces many
subjectiveSubjectivity refers to a person's perspective or opinion, particular feelings, beliefs, and desires. It is often used casually to refer to unsubstantiated personal opinions, in contrast to knowledge and fact-based beliefs. In philosophy, the term is often contrasted with...
effects, such as greater enjoyment of food taste and aroma, an enhanced enjoyment of music and comedy, and marked distortions in the perception of time and space (where experiencing an up rush of ideas from the bank of long-term memory can create the subjective impression of long elapsed time, while a clock reveals that only a short time has passed). At higher doses, effects can include altered
body imageBody image is a term which may refer to a person's perception of his or her own physical appearance, or the interpretation of the body by the brain...
, auditory and/or visual illusions, and
ataxiaAtaxia is a neurological sign and symptom consisting of gross lack of coordination of muscle movements. Ataxia is a non-specific clinical manifestation implying dysfunction of parts of the nervous system that coordinate movement, such as the cerebellum...
from selective impairment of polysynaptic reflexes. In rare cases, cannabis can lead to
depersonalizationDepersonalization is a malfunction or anomaly of the mechanism by which an individual has self awareness. It is a feeling of watching oneself act, while having no control over a situation...
and
derealizationDerealization is an alteration in the perception or experience of the external world so that it seems strange or unreal. Other symptoms include feeling as though one's environment is lacking in spontaneity, emotional colouring and depth. It is a dissociative symptom of many conditions, such as...
; such effects are most often considered desirable.
Somatic effects
Some of the short-term physical effects of cannabis use include increased
heart rateHeart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute , it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and...
,
dry mouthXerostomia is the medical term for the subjective complaint of dry mouth due to a lack of saliva. Xerostomia is sometimes colloquially called pasties, cottonmouth, doughmouth or des . Xerostomia is also common in smokers....
, reddening of the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
s (congestion of the
conjunctivaThe conjunctiva is a clear mucous membrane consisting of cells and underlying basement membrane that covers the sclera and lines the inside of the eyelids...
l
blood vesselThe blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart, the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s), a reduction in intra-ocular pressure, muscle relaxation and a sensation of cold or hot hands and feet.
ElectroencephalographyElectroencephalography is the recording of electrical activity along the scalp produced by the firing of neurons within the brain . In clinical contexts, EEG refers to the recording of the brain's spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from...
or EEG shows somewhat more persistent
alpha waveAlpha waves are electromagnetic oscillations in the frequency range of 8–12 Hz arising from synchronous and coherent electrical activity of thalamic pacemaker cells...
s of slightly lower
frequencyFrequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
than usual. Cannabinoids produce a "marked depression of motor activity" via activation of neuronal cannabinoid receptors belonging to the
CB1CB1 may refer to:* CB postcode area - the Cambridge postcode area* Cannabinoid receptor 1 - a receptor for cannabinoids in the brain* Crash Bandicoot, the first game in the Crash Bandicoot series...
subtype.
Duration
The total short-term duration of cannabis intoxication when smoked is based on the potency and how much is smoked. Effects can typically last two to three hours for one gram.
A study of ten healthy, robust, male volunteers who resided in a residential research facility sought to examine both acute and residual subjective, physiologic, and performance effects of smoking marijuana cigarettes. On three separate days, subjects smoked one
NIDAThe National Institute on Drug Abuse is a United States federal-government research institute whose mission is to "lead the Nation in bringing the power of science to bear on drug abuse and addiction."-History:...
marijuana cigarette containing either 0%, 1.8%, or 3.6% THC, documenting subjective, physiologic, and performance measures prior to smoking, five times following smoking on that day, and three times on the following morning. Subjects reported robust subjective effects following both active doses of marijuana, which returned to baseline levels within 3.5 hours. Heart rate increased and the pupillary light reflex decreased following active dose administration with return to baseline on that day. Additionally, marijuana smoking acutely produced decrements in smooth pursuit eye tracking. Although robust acute effects of marijuana were found on subjective and physiological measures, no effects were evident the day following administration, indicating that the residual effects of smoking a single marijuana cigarette are minimal.
A Dutch double blind, randomized, placebo-controlled, cross-over study examining male volunteers aged 18–45 years with a self-reported history of regular cannabis use concluded that smoking of cannabis with very high THC levels (marijuana with 9–23% THC), as currently sold in coffee shops in the Netherlands, may lead to higher THC blood-serum concentrations. This is reflected by an increase of the occurrence of impaired psychomotor skills, particularly among younger or inexperienced cannabis smokers, who do not adapt their smoking-style to the higher THC content. High THC concentrations in cannabis were associated with a dose-related increase of physical effects (such as increase of heart rate, and decrease of blood pressure) and psychomotor effects (such as reacting more slowly, being less concentrated, making more mistakes during performance testing, having less motor control, and experiencing drowsiness). It was also observed during the study that the effects from a single
jointJoint is slang for a cigarette rolled using cannabis. Rolling papers are the most common rolling medium among industrialized countries, however brown paper, cigarettes with the tobacco removed, and newspaper are commonly used throughout the developing world. Modern papers are now commonly made...
lasted for more than eight hours. Reaction times remained impaired five hours after smoking, when the THC serum concentrations were significantly reduced, but still present. When subjects smoke on several occasions per day, accumulation of THC in blood-serum may occur.
Neurological effects
The areas of the brain where cannabinoid receptors are most prevalently located are consistent with the
behavioralHuman behavior is the collection of behaviors exhibited by human beings and influenced by culture, attitudes, emotions, values, ethics, authority, rapport, hypnosis, persuasion, coercion and/or genetics....
effects produced by cannabinoids. Brain regions in which cannabinoid receptors are very abundant are the
basal gangliaThe basal ganglia are a group of nuclei in the brains of vertebrates, situated at the base of the forebrain and strongly connected with the cerebral cortex, thalamus and other areas. The basal ganglia are associated with a variety of functions, including motor control and learning...
, associated with movement control; the
cerebellumThe cerebellum is a region of the brain that plays an important role in the integration of sensory perception, coordination and motor control...
, associated with body movement coordination; the
hippocampusThe hippocampus is a major component of the brains of humans and other mammals. It belongs to the limbic system and plays important roles in long-term memory and spatial navigation. Like the cerebral cortex, with which it is closely associated, it is a paired structure, with mirror-image halves in...
, associated with
learningLearning is acquiring new knowledge, behaviors, skills, values, preferences or understanding, and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning may...
, memory, and
stressStress is a biological term for the consequences of the failure of a human or animal to respond appropriately to emotional or physical threats to the organism, whether actual or imagined....
control; the
cerebral cortexThe cerebral cortex is a structure within the brain that plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It constitutes the outermost layer of the cerebrum. In preserved brains, it has a grey color, hence the name "grey matter"...
, associated with higher cognitive functions; and the
nucleus accumbensThe nucleus accumbens , also known as the accumbens nucleus or as the nucleus accumbens septi , is a collection of neurons within the striatum. It is thought to play an important role in reward, laughter, pleasure, addiction, fear, and the placebo effect.Each half of the brain has one nucleus...
, regarded as the reward center of the brain. Other regions where cannabinoid receptors are moderately concentrated are the
hypothalamusThe hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions. One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland ....
, which regulates homeostatic functions; the
amygdalaThe ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans...
, associated with emotional responses and
fearFear is an emotional response to a threat. It is a basic survival mechanism occurring in response to a specific stimulus, such as pain or the threat of danger. Some psychologists such as John B. Watson, Robert Plutchik, and Paul Ekman have suggested that fear is one of a small set of basic or...
s; the
spinal cordThe spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain. The brain and spinal cord together make up the central nervous system. It is around 45 cm long in men and around 43 cm long in women. The length of the spinal cord is much shorter than...
, associated with peripheral sensations like pain; the
brain stemThe brainstem is the lower part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
, associated with
sleepSleep is a naturally recurring state of relatively suspended sensory and motor activity, characterized by total or partial unconsciousness and the inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and it is more easily...
,
arousalArousal is a physiological and psychological state of being awake. It involves the activation of the reticular activating system in the brain stem, the autonomic nervous system and the endocrine system, leading to increased heart rate and blood pressure and a condition of sensory alertness,...
, and motor control; and the
nucleus of the solitary tractThe solitary tract and nucleus are structures in the brainstem that carry and receive visceral sensation and taste from the facial , glossopharyngeal and vagus cranial nerves.-Anatomy:...
, associated with visceral sensations like
nauseaNausea is the sensation of unease and discomfort in the stomach with an urge to vomit.-Causes:...
and
vomitingVomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose. Undesired vomiting may result from many causes, ranging from gastritis or poisoning to brain tumors, or elevated intracranial pressure...
.
Most notably, the two areas of motor control and memory are where the effects of cannabis are directly and irrefutably evident. Cannabinoids, depending on the
doseDose means quantity in the following fields:In nutrition, medicine, and toxicology:* Dose , the quantity of something that may be eaten by or administered to an organism, or that an organism may be exposed to...
, inhibit the transmission of neural signals through the basal ganglia and cerebellum. At lower doses, cannabinoids seem to stimulate locomotion while greater doses inhibit it, most commonly manifested by lack of steadiness (body sway and hand steadiness) in motor tasks that require a lot of attention. Other brain regions, like the cortex, the cerebellum, and the neural pathway from cortex to
striatumThe striatum also known as striate body or striate nucleus is a subcortical part of the telencephalon/cerebrum. It is the major input station of the basal ganglia system...
, are also involved in the control of movement and contain abundant cannabinoid receptors, indicating their possible involvement as well.
Experiments on animal and human tissue have demonstrated disruption of
short-term memoryShort-term memory refers to the capacity for holding a small amount of information in mind in an active, readily available state for a short period of time. The duration of short-term memory is believed to be in the order of seconds...
, which is consistent with the abundance of CB1 receptors on the hippocampus, the region of the brain most closely associated with memory. Cannabinoids inhibit the release of several neurotransmitters in the hippocampus, like
acetylcholineThe chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans. Acetylcholine is one of many neurotransmitters in the autonomic nervous system and the only neurotransmitter used in the motor division...
,
norepinephrineNoradrenaline or norepinephrine is a catecholamine with dual roles as a hormone and a neurotransmitter....
, and glutamate, resulting in a major decrease in neuronal activity in that region. This decrease in activity resembles a "temporary hippocampal lesion." In the end, this procedure could lead to the blocking of cellular processes that are associated with memory formation.
In
in-vitro experiments THC at extremely high concentrations, which could not be reached with commonly consumed doses, caused
competitive inhibitionCompetitive inhibition is a form of enzyme inhibition where binding of the inhibitor to the enzyme prevents binding of the substrate and vice versa.-Mechanism:...
of the
AChEAche may refer to:* Ache , a You've Got Foetus on Your Breath album* Ache , a song by No Doubt* Ache Records, a Vancouver-based record label* Ache, a chronic, painful sensation* The American College of Healthcare Executives...
enzyme and inhibition of
β-amyloidAmyloid beta is a peptide of 39–43 amino acids that appear to be the main constituent of amyloid plaques in the brains of Alzheimer's disease patients. Similar plaques appear in some variants of Lewy body dementia and in inclusion body myositis, a muscle disease. Aβ also forms aggregates coating...
peptide aggregation, the cause of
Alzheimer's diseaseAlzheimer's disease , also called Alzheimer disease, Senile Dementia of the Alzheimer Type or simply Alzheimer's, is the most common form of dementia. This incurable, degenerative, and terminal disease was first described by German psychiatrist and neuropathologist Alois Alzheimer in 1906 and was...
. Compared to currently approved drugs prescribed for the treatment of Alzheimer's disease, THC is a considerably superior inhibitor of A aggregation, and this study provides a previously unrecognized molecular mechanism through which cannabinoid molecules may directly impact the progression of this debilitating disease.
Effects on driving
It is known that cannabis consumption affects
motor skillA motor skill is a learned series of movements that combine to produce a smooth, efficient action.* Gross motor skills include lifting one's head, rolling over, sitting up, balancing, crawling, and walking. Gross motor development usually follows a pattern...
s,
reflexA reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. In most contexts, in particular those involving humans, reflex actions are mediated via the reflex arc; this is not always true in other animals, nor does it apply to casual uses...
es, and
attentionAttention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources...
; not necessarily meaning that it affects driving ability.
A 2001 study by the United Kingdom Transit Research Laboratory (TRL) specifically focuses on the effects of cannabis use on driving, and is one of the most recent and commonly quoted studies on the subject. The report summarizes current knowledge about the effects of cannabis on driving and accident risk based on a review of available literature published since 1994 and the effects of cannabis on laboratory based tasks.
The study identified young males, amongst whom cannabis consumption is frequent and increasing, and in whom alcohol consumption is also common, as a risk group for traffic accidents. This is due to driving inexperience and factors associated with youth relating to
riskRisk is a concept that denotes the precise probability of specific eventualities. Technically, the notion of risk is independent from the notion of value and, as such, eventualities may have both beneficial and adverse consequences...
taking,
delinquencyA delinquent is one who fails to do that which is required by law or by duty when such failure is minor in nature.The term is often used to refer to a juvenile who commits a minor criminal act—juvenile delinquents....
and
motivationMotivation is the activation or energization of goal-oriented behavior. Motivation may be internal or external. The term is generally used for humans but, theoretically, it can also be used to describe the causes for animal behavior as well. This article refers to human motivation...
. These demographic and psychosocial variables may relate to both drug use and accident risk, thereby presenting an artificial relationship between use of drugs and accident involvement.
The effects of cannabis on laboratory-based tasks show clear impairment with respect to tracking ability,
attentionAttention is the cognitive process of selectively concentrating on one aspect of the environment while ignoring other things. Attention has also been referred to as the allocation of processing resources...
, and other tasks depending on the dose administered. These effects however, are not as pronounced on real world tasks, like driving or
simulatorDriving Simulators are used for entertainment as well as in training of driver's education courses taught in educational institutions and private businesses...
tasks. Both simulation and road trials generally find that driving behavior shortly after consumption of larger doses of cannabis results in:
- increased variability in lane position (such as taking a curve too tightly or too loosely).
- longer decision times, leading to slower responses to driving situations; and
- a more cautious driving style, including slower average speed and greater following distance.
Kelly, Darke and Ross show similar results, with laboratory studies examining the effects of cannabis on skills utilised while driving showing impairments in tracking, attention, reaction time, short-term memory, hand-eye coordination, vigilance, time and distance perception, and decision making and concentration. An EMCDDA review concluded that "the acute effect of moderate of higher doses of cannabis impairs the skills related to safe driving and injury risk", specifically "attention, tracking and psychomotor skills".
In their review of driving simulator studies, Kelly et al conclude that there is evidence of dose-dependent impairments in cannabis-affected drivers' ability to control a vehicle in the areas of steering, headway control, speed variability, car following, reaction time and lane positioning. The researchers note that "even in those who learn to compensate for a drug's impairing effects, substantial impairment in performance can still be observed under conditions of general task performance (ie. when no contingencies are present to maintain compensated performance."
Whereas these results indicate a 'change' from normal conditions, they do not necessarily reflect 'impairment' in terms of performance effectiveness, since few studies report increased accident risk. However, the results do suggest 'impairment' in terms of performance efficiency given that some of these behaviors may limit the available resources to cope with any additional, unexpected or high demand, events. Indeed, compensatory effort may be invoked to offset impairment in the driving task. Subjects under cannabis treatment may perceive that they are impaired and may strategically compensate, for example, by not overtaking, by slowing down and by focusing their attention when they know a response will be required. This compensatory effort may be one reason for the failure to implicate cannabis consumption as an accident
risk factorA risk factor is a variable associated with an increased risk of disease or infection. Risk factors are correlational and not necessarily causal, because correlation does not imply causation...
, particularly at lower doses or with more than about one hour after consumption. According to the TRL study, the same compensatory behavior could also be an unconscious adaptation, similar to reduced driving speeds used by a sleepy driver.
Specifically, 4-12% of accident fatalities have detected levels of cannabis.However, most studies report that the majority of fatal cases with detected levels of cannabis are compounded by alcohol. The study estimates 11 ng/ml THC as the equivalent dose to the legal limit of alcohol (0.08% BAC in the UK). Complicating this assessment is the fact that cannabis effects on driving fade after a short period of time, while some THC may be present in the body for weeks.
Grotenherman et al conclude that after reviewing the limited epidemiological and laboratory evidence, driving under the influence of cannabis appears to increase the risk of motor vehicle crashes by a factor of two to three times. In their review of recent studies featuring blood samples that detect active THC metabolites, Ramaeters et al concluded that although crash culpability was not elevated for low concentrations of THC, risk of involvement in a traffic crash increased as drivers' THC levels increased, and became up to 6.6 times greater than that for drug-free drivers, at higher concentrations of THC.
Similar conclusions have been reached by studies maintained by the federal governments of
AustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the continental mainland , the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans...
, United Kingdom,
New ZealandNew Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses , and numerous smaller islands, most notably Stewart Island/Rakiura and the Chatham Islands. The indigenous Māori named New Zealand Aotearoa, commonly translated as The Land of the Long White Cloud...
and the United States (see
here for a list of studies). Those studies that have concluded that cannabis has a significant negative effect on driving ability generally involve the use of roadside sobriety tests as an indicator of reduced ability (for example, see
this NIDA report). Driver culpability studies in Australia have suggested that drivers testing positive to cannabis are significantly more likely to be responsible for fatal car crashes than drug-free drivers.
However, studies that employ this methodology show that a majority of subjects who tested positive for THC also tested positive for alcohol, already described as a limiting factor of validity. Kelly et al conclude that the combined effects of cannabis and alcohol on laboratory performance measures are typically greater then the effects of cannabis alone, and act in either an additive or multiplicative manner. Increasing recognition of limitations on driving skill when the driver tests positive to cannabis has resulted in the development of guidelines for research on drugged driving
Vascular effects
Cannabis arteritis is a very rare peripheral vascular disease similar to
Buerger's diseaseBuergers's disease is a recurring inflammation and thrombosis of small and medium arteries and veins of the hands and feet...
. There were about 50 confirmed cases from 1960 to 2008.
A 2008 study by the
National Institutes of HealthThe National Institutes of Health is an agency of the United States Department of Health and Human Services and is the primary agency of the United States government responsible for biomedical and health-related research. It consists of 27 separate institutes and centers which includes the Office...
Biomedical Research Centre in Baltimore found that heavy, chronic smoking of marijuana changed
blood proteinsBlood proteins, also called serum proteins, are proteins found in blood plasma. Serum total protein in blood is 7g/dl, which in total makes 7% of total blood volume...
associated with
heart diseaseHeart disease or cardiopathy is an umbrella term for a variety for different diseases affecting the heart. As of 2007, it is the leading cause of death in the United States, England, Canada and Wales, killing one person every 34 seconds in the United States alone.-Coronary heart disease:Coronary...
and
strokeA stroke is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by thrombosis or embolism or due to a hemorrhage...
. A 2005 study by the
National Institute on Drug AbuseThe National Institute on Drug Abuse is a United States federal-government research institute whose mission is to "lead the Nation in bringing the power of science to bear on drug abuse and addiction."-History:...
found that moderate to heavy marijuana use has an effect on blood flow to the brain, potentially increasing the risk of memory damage and stroke.
A 2005 article in the
Journal of Neurology, Neurosurgery and Psychiatry reported on a 36-year-old man who suffered a stroke on three separate occasions after smoking a large amounts of marijuana, despite having no known risk factors for the disorder, suggesting that a rare side effect of marijuana use may be an increase in the incidence of strokes among young smokers. A 2000 study by researchers at Boston's
Beth Israel Deaconess Medical CenterBoth an international and regional referral center, Beth Israel Deaconess Medical Center in Boston, Massachusetts is a major teaching hospital of Harvard Medical School. It was formed out of the 1996 merger of Beth Israel Hospital and New England Deaconess Hospital...
,
Massachusetts General HospitalMassachusetts General Hospital is a teaching hospital of Harvard Medical School and a biomedical research facility in Boston, Massachusetts....
and
Harvard School of Public HealthThe Harvard School of Public Health is one of the professional graduate schools of Harvard University. Located in Longwood Area of the Boston, Massachusetts neighborhood of Mission Hill, next to Harvard Medical School and Cambridge, Massachusetts, HSPH is considered one of the most prestigious...
also found that a middle-age person's risk of heart attack rises nearly fivefold in the first hour after smoking marijuana.
Adulterated cannabis
Contaminants may be found in
hashishHashish is a preparation of cannabis composed of the compressed stalked resin glands called trichomes, collected from the cannabis plant. It contains the same active ingredients but in higher concentrations than other parts of the plant such as the buds or the leaves...
obtained from "soap bar"-type sources. The dried flowers of the plant may be contaminated by the plant taking up heavy metals and other toxins from its growing environment, or by the addition of lead or glass beads, used to increase the weight or to make the cannabis appear as if it has more crystal-looking trichomes indicating a higher THC content. Users who burn hot or mix cannabis with tobacco are at risk of failing to detect deviations from appropriate cannabis taste.
Despite cannabis being generally perceived as a natural or chemical-free product, in a recent Australian survey one in four Australians consider cannabis grown indoors under hydroponic conditions to be a greater health risk due to increased contamination, added to the plant during cultivation to enhance the actual or perceived plant growth and quality.
Combination with other drugs
The most obvious confounding factor in cannabis research is the prevalent usage of other recreational drugs, especially
alcoholIn chemistry, an alcohol is any organic compound in which a hydroxyl group is bound to a carbon atom of an alkyl or substituted alkyl group. An important group of acohols is formed by the simple acyclic alcohols, the general formula for which is C
nH
2n+1OH...
and tobacco. Such complications demonstrate the need for studies on cannabis that have stronger controls, and investigations into alleged symptoms of cannabis use that may also be caused by tobacco. Some critics question whether agencies doing the research make an honest effort to present an accurate, unbiased summary of the evidence, or whether they "
cherry-pickConfirmation bias is an irrational tendency to search for, interpret or remember information in a way that confirms preconceptions or working hypotheses. It is a type of cognitive bias and a systematic error of inductive reasoning...
" their data to please funding sources which may include the tobacco industry or governments dependent on cigarette tax revenue; others caution that the raw data, and not the final conclusions, are what should be examined.
Cannabis also has been shown to have a synergistic cytotoxic effect on lung cancer cell cultures in vitro with the food additive
butylated hydroxyanisoleE320 redirects here. For the automobile, see Mercedes-Benz E-Class.Butylated hydroxyanisole is an antioxidant consisting of a mixture of two isomeric organic compounds, 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. It is prepared from 4-methoxyphenol and isobutylene...
(BHA) and possibly the related compound
butylated hydroxytolueneButylated hydroxytoluene , also known as butylhydroxytoluene, is a lipophilic organic compound that is primarily used as an antioxidant food additive as well as in cosmetics, pharmaceuticals, jet fuels, rubber, petroleum products, electrical transformer oil, and embalming fluid.-Production:BHT is...
(BHT). The study concluded, "Exposure to marijuana smoke in conjunction with BHA, a common food additive, may promote deleterious health effects in the lung." BHA & BHT are human-made fat preservatives, and are found in many packaged foods including: plastics in boxed Cereal, Jello, Slim Jims, and more.
The Australian National Household Survey
http://www.http://www.aihw.gov.au/publications/index.cfm/title/8227 of 2001 showed that cannabis use in Australia is rarely used without other drugs. 95% of cannabis users also drank alcohol; 26% took amphetamines; 19% took ecstasy and only 2.7% reported not having used any other drug with cannabis. While research has been undertaken on the combined effects of alcohol and cannabis on performing certain tasks, little research has been conducted on the reasons why this combination is so popular. Evidence from a controlled experimental study undertaken by Lukas and Orozco suggests that alcohol causes THC to be absorbed more rapidly into the blood plasma of the user. Data from the Australian National Survey of Mental Health and Wellbeing
http://www.http://docs.google.com/gview?a=v&q=cache%3AT-P5PXv-rtoJ%3Awww.health.act.gov.au%2Fc%2Fhealth%3Fa%3Dsendfile%26ft%3Dp%26fid%3D1055726773%26sid%3D+1997+australian+national+survey+of+mental+health+and+Wellbeing&hl=en&gl=au&sig=AFQjCNHEL2Sjfp7LT_i3Iftg7paFhIjHqQ&pli=1found that three-quarters of recent cannabis users reported using alcohol when cannabis was not available.
Memory and learning
Studies on cannabis and memory are hindered by small sample sizes, confounding drug abuse, and other factors. The strongest evidence regarding cannabis and memory focuses on its short-term negative effects on short-term and working memory.
A 2008 review of the evidence surrounding the acute impact on memory concluded that cannabinoids impair all aspects of short-term memory, especially short-term episodic and working memory. One small study found that no learning occurred during the 2 hour period in which the subjects (infrequent users) were "stoned".
Appetite
The feeling of increased appetite following the use of
cannabisCannabis is a genus of flowering plants that includes three putative species, Cannabis sativa L., Cannabis indica Lam., and Cannabis ruderalis Janisch. These three taxa are indigenous to Central Asia, and South Asia. Cannabis has long been used for fibre , for medicinal purposes, and as a...
has been documented for hundreds of years, and is commonly known as 'the munchies' in popular culture. Clinical studies and survey data have found that cannabis increases food enjoyment and interest in food. Scientists have claimed to be able to explain what causes the increase in appetite, concluding that "endocannabinoids in the hypothalamus activate cannabinoid receptors that are responsible for maintaining food intake".
Endogenous cannabinoids have recently been discovered in foods such as chocolate and human and bovine milk.
It is widely accepted that the neonatal survival of many species "is largely dependent upon their suckling behavior, or appetite for breast milk" and recent research has identified the endogenous cannabinoid system to be the first neural system to display complete control over milk ingestion and neonatal survival. It is possible that "cannabinoid receptors in our body interact with the cannabinoids in milk to stimulate a suckling response in newborns so as to prevent growth failure".
Reproductive effects
Cannabis has been reported both to enhance and lessen the subjective enjoyment of sex. It has been shown that administration of high doses of THC to animals lowers serum
testosteroneTestosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid.In men,...
levels, impairs
spermA sperm, from the ancient Greek word σπέρμα and and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.Sperm cells contribute...
production, motility, and viability, disrupts the
ovulationOvulation is the process in the females menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum that participates in reproduction...
cycle, and decreases output of
gonadotropic hormonesGonadotropes are basophilic cells in the anterior pituitary that produce the gonadotropins follicle-stimulating hormone and luteinizing hormone . Release of FSH and LH by gonadotrophs is regulated by gonadotropin-releasing hormone from the hypothalamus....
. According to the 1997
Merck Manual of Diagnosis and TherapyThe Merck Manual of Diagnosis and Therapy, often called simply The Merck Manual, is the world's best-selling medical textbook. First published in 1899, it is now in its 18th edition.-The "Professional Edition":...
, fertility effects related to cannabis use are uncertain.
Research has demonstrated that human
spermThe term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
contains receptors which are stimulated by substances like THC and other cannabis-related chemicals. Tests have implied that smoking of marijuana could impact the sperm's functions, though this impact is unknown.. There is some evidence that cannabis may compromise female fertility with a modest association reported between cannabis use and infertility in Mueller et al'scase controlled study of 150 women with primary anovulatory infertility. While Wenger et al indicate evidence that THC and anandamide increase the duration of pregnancy and increase the frequency of stillbirth in rats. In a report prepared for the Australian National Council on Drugs, Copeland, Gerber and Swift conclude that current understanding suggests cannabis-related substances are contraindicated in pregnancy, as are compounds that interact with endocannabinoid synthesis and metabolism.
Pregnancy
A 1989 study of 1226 mothers published in the
New England Journal of MedicineThe New England Journal of Medicine is an English-language peer-reviewed medical journal published by the Massachusetts Medical Society. It is the oldest continuously published medical journal in the world, and is the most widely read, cited, and influential general medical periodical in the...
concluded that "the use of marijuana or cocaine during pregnancy is associated with impaired fetal growth". Compared to
fetal alcohol syndromeFetal alcohol syndrome is a disorder that can occur to the embryo when a pregnant woman ingests alcohol during pregnancy. An ingestion of alcohol does not always result in FAS...
, similar types of facial features and related symptoms are not associated with prenatal marijuana exposure. THC passes into the
breast milkHuman breast milk refers to the milk produced by a mother to feed her baby. It provides the primary source of nutrition for newborns before they are able to eat and digest other foods; older infants and toddlers may continue to be breastfed...
and
might affect a breastfed
infantAn infant or baby is the term used to refer to the very young offspring of humans and other primates.-Infant:The term infant derives from the Latin word infans, meaning "unable to speak."...
. Many studies about drug use during pregnancy are self-administered by the applicants and not always
anonymousAnonymity is derived from the Greek word ανωνυμία, meaning "without a name" or "namelessness". In colloquial use, anonymous typically refers to a person, and often means that the personal identity, or personally identifiable information of that person is not known.More strictly, and in reference to...
. The
stigmaSocial stigma is severe social disapproval of personal characteristics or beliefs that are perceived to be against cultural norms. Stigma is often based on ignorance, irrational or unfounded fears, mass hysteria, lack of education, or a lack of information pertaining to a particular person or group...
of using illicit drugs while pregnant discourages honest reporting and can invalidate the results. Studies show that women who consume cannabis while they are pregnant may also be likely to consume
alcoholEthanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug, best known as the type of alcohol found in alcoholic beverages and in modern thermometers. Ethanol is one of the oldest recreational drugs...
,
tobaccoTobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as an organic pesticide, and in the form of nicotine tartrate it is used in some medicines. In consumption it most commonly appears in the forms of smoking, chewing, snuffing, or...
,
caffeineCaffeine is a bitter, white crystalline xanthine alkaloid that is a psychoactive stimulant drug. Caffeine was discovered by a German chemist, Friedrich Ferdinand Runge, in 1819. He coined the term kaffein, a chemical compound in coffee, which in English became caffeine...
, or other illicit drugs, which makes it difficult to deduce scientific facts about just marijuana use from statistical results. Very few large, well-controlled
epidemiologicalEpidemiology is the study of factors affecting the health and illness of populations, and serves as the foundation and logic of interventions made in the interest of public health and preventive medicine...
studies have taken place to understand the connection of marijuana use and pregnancy.
A study of the development of 59
JamaicaJamaica is an island nation of the Greater Antilles, in length and as much as in width, amounting to 11,100 km
2. It is situated in the Caribbean Sea, about south of Cuba, and west of Hispaniola, the island harboring the nation-states Haiti and the Dominican Republic...
n children was conducted with the children being monitored from child birth to age 5 years. One-half of the sample's
motherA mother is a biological and/or social female parent of an offspring. Because of the complexity and differences of a mothers' social, cultural, and religious definitions and roles, it is challenging to define a mother to suit a universally accepted definition.-Biological mother:In the case of a...
s used marijuana during pregnancy; they were paired with non-using mothers who matched
ageAgeing or aging is the accumulation of changes in an organism or object over time. Ageing in humans refers to a multidimensional process of physical, psychological, and social change. Some dimensions of ageing grow and expand over time, while others decline...
, parity, and socioeconomic status. Testing was done at 1, 3, and 30 days of age with the Brazelton Neonatal Behavioral Assessment Scales, and at ages 4 and 5 years with the McCarthy Scales of Children's Abilities test. Data was also collected from the child's home environment and temperament, as well as standardized tests. The results over the entire research period showed no significant differences in development testing outcomes between using and non-using mothers. At 30 days of age, however, the children of marijuana-using mothers had higher scores on autonomic stability and reflexes. The absence of any differences between the exposed and non-exposed groups in the early neonatal period suggest that the better scores of exposed neonates at 1 month are traceable to the cultural positioning and social and economic characteristics of mothers using marijuana that select for the use of marijuana but also promote neonatal development.
Some studies have found that children of tobacco and marijuana-smoking mothers more frequently suffer from permanent cognitive deficits, concentration disorders, hyperactivity, and impaired social interactions than non-exposed children of the same age and social background. A recent study, with participation of scientists from Europe and the United States, has now identified that
naturally occurringThe word endogenous means "proceeding from within", the opposite of exogenous.-Biology:Endogenous substances are those that originate from within an organism, tissue, or cell . Endogenous retrovirus are caused by ancient infections of germ cells in humans, mammals and other vertebrates...
endocannabinoid molecules play a role in establishing how certain nerve cells connect to each other in the fetal brain. Another study examining cannabinoid receptor proteins (CBRs) expressed in brain cells of mice determined that endogenous endocannabinoids assist in directing
brain cellBrain cell is a generic term for neurons and glial cells. Neurons are nerve cells that process and transmit information through the nervous system. Glial cells provide support, protection, and nutrition to neurons. Other cells in the brain include epithelial cells that make up the lining of the...
directional development while in the womb. The researchers suggest that elevated blood THC levels due to cannabis consumption would affect brain development of human fetuses. In contrast, other studies in Jamaica have suggested that cannabis use by expectant mothers does not appear to cause birth defects or developmental delays in their newborn children.
Addiction potential
Research has shown the overall addiction potential for cannabis to be much less than for tobacco, alcohol, cocaine or heroin. There is some evidence that dependence on cannabis can exist in some heavy users. One study with 500 heavy users of cannabis showed that when trying to cease consumption, some experience one or more symptoms such as
insomniaInsomnia is a symptom of any of several sleep disorders, characterized by persistent difficulty falling asleep or staying asleep despite the opportunity. Insomnia is a symptom, not a stand-alone diagnosis or a disease. By definition, insomnia is "difficulty initiating or maintaining sleep, or both"...
, restlessness, loss of
appetiteThe appetite is the desire to eat food, felt as hunger. Appetite exists in all higher life-forms, and serves to regulate adequate energy intake to maintain metabolic needs. It is regulated by a close interplay between the digestive tract, adipose tissue and the brain. Decreased desire to eat is...
,
depressionIn psychology and psychiatry, depression is a state of low mood and aversion to activity. While most often described as a disease or dysfunction, there are also strong arguments for seeing depression as an adaptive defense mechanism....
,
irritabilityIrritability is an excessive response to stimuli. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessive sensitivity to stimuli....
, and
angerAnger is an emotion. The physical effects of anger include increased heart rate, blood pressure, and levels of adrenaline and noradrenaline. Some view anger as part of the fight or flight brain response to the perceived threat of harm...
. Prolonged marijuana use produces both pharmacokinetic changes (how the drug is absorbed, distributed, metabolized, and excreted) and pharmacodynamic changes (how the drug interacts with target cells) to the body. These changes require the user to consume higher doses of the drug to achieve a common desirable effect (known as a higher tolerance), and reinforce the body’s metabolic systems for synthesizing and eliminating the drug more efficiently.
Preliminary research, published in the April 2006 issue of the
Journal of Consulting and Clinical Psychology, indicates that cannabis addiction can be offset by a combination of
cognitive-behavioral therapyCognitive behavioral therapy is a psychotherapeutic approach that aims to solve problems concerning dysfunctional emotions, behaviors and cognitions through a goal-oriented, systematic procedure...
and motivational incentives. Participants in the study (previously diagnosed with marijuana dependence) received either vouchers as incentives to stay drug free, cognitive-behavioral therapy, or both over a 14-week period. At the end of 3 months, 43 percent of those who received both treatments were no longer using marijuana, compared with 40 percent of the voucher group, and 30 percent of the therapy group. At the end of a 12-month follow-up, 37 percent of those who got both treatments remained abstinent, compared with 17 percent of the voucher group, and 23 percent of the therapy group.
A 1998 French governmental report commissioned by Health Secretary of State
Bernard Kouchner Bernard Kouchner is a French politician, diplomat, and doctor. He is co-founder of Médecins Sans Frontières -- also known as Doctors Without Borders -- and Doctors of the World...
, and directed by Dr. Pierre-Bernard Roques, classed drugs according to addictiveness and
neurotoxicityNeurotoxicity occurs when the exposure to natural or artificial toxic substances, which are called neurotoxins, alters the normal activity of the nervous system in such a way as to cause damage to nervous tissue. This can eventually disrupt or even kill neurons, key cells that transmit and process...
. It placed heroin, cocaine and alcohol in the most addictive and lethal categories;
benzodiazepineA benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...
, hallucinogens and tobacco in the medium category, and cannabis in the last category. The report stated that "Addiction to cannabis does not involve neurotoxicity such as it was defined in chapter 3 by neuroanatomical, neurochemical and behavioral criteria. Thus, former results suggesting anatomic changes in the brain of chronic cannabis users, measured by
tomographyTomography is imaging by sections or sectioning, through the use of wave of energy. A device used in tomography is called a tomograph, while the image produced is a tomogram. The method is used in medicine, archaeology, biology, geophysics, oceanography, materials science, astrophysics and other...
, were not confirmed by the accurate modern
neuro-imaging techniquesMagnetic Resonance Imaging , or nuclear magnetic resonance imaging , is primarily a medical imaging technique most commonly used in radiology to visualize the internal structure and function of the body...
. Moreover, morphological impairment of the hippocampus [which plays a part in memory and navigation] of rat after administration of very high doses of THC (Langfield
et al., 1988) was not shown (Slikker
et al., 1992)." Health Secretary Bernard Kouchner concluded that : "Scientific facts show that, for cannabis, no neurotoxicity is demonstrated, to the contrary of alcohol and cocaine."
In treating marijuana use, Dr.
David McDowellDavid M. McDowell is a psychiatrist, author and creative consultant. He co-founded the Substance Treatment and Research Service at Columbia University and served as its medical director...
of
Columbia UniversityColumbia University in the City of New York is a private university in the United States and a member of the Ivy League. Columbia's main campus lies in the Morningside Heights neighborhood in the borough of Manhattan, in New York City...
found that there is a need for the clinician to differentiate in the spectrum between a casual user who still has difficulty with drug screens, and a daily, heavy user. McDowell found that the sedating and
anxiolyticAn anxiolytic is a drug used for the treatment of symptoms of anxiety. Anxiolytics have been shown to be useful in the treatment of anxiety disorders, as have antidepressants such as the selective serotonin reuptake inhibitors .Though not anxiolytics, beta-receptor blockers such as propranolol and...
properties of
THCThe acronym THC has several possible meanings:* Tetrahydrocannabinol, the main active chemical compound in Cannabis* Toronto Hemp Company, the world's largest Hemp and Cannabis Culture store, located in Toronto, Canada....
might make the use of cannabis an attempt to self-medicate
personalityPersonality disorders, formerly referred to as character disorders, are a class of personality types which deviate from the contemporary expectations of a society....
or psychiatric disorders.
Mental health
Cannabis use has been assessed by several studies to be
correlated with the developmentThe term dual diagnosis is used to describe the comorbid condition of a person considered to be suffering from a mental illness and a substance abuse problem. There is considerable debate surrounding the appropriateness of the term being used to describe a heterogeneous group of individuals with...
of anxiety, psychosis, and depression. Some studies assess that the causality is more likely to involve a path from cannabis use to psychotic symptoms rather than a path from psychotic symptoms to cannabis use, while others assess the opposite direction of the causality, or hold cannabis to only form parts of the "causal constellation", while not inflicting mental health problems that would have occurred in the absence of the cannabis use. A common interpretation of the correlation and theorized direction of the causality is the self-medication hypothesis, which is based on partially or fully attributing the correlation between psychiatric diseases and cannabis to the extensive substance abuse among sufferers of certain mental disorders, before diagnosis in many cases, which increases the likeliness of cannabis use among the mentally ill and the undiagnosed, thus accounting for correlation and debunking some claims of causality with the opposite direction. As much as 60% of the mentally ill are suspected to be substance abusers, and many seem to prefer cannabis and alcohol.
Dr Stanley Zammit of Bristol and Cardiff universities (in the Daily Express newspaper of the 27th of July 2007) reported "Even if cannabis did increase the risk of psychosis, most people using the drug would not get ill" But he added: "Nevertheless, we would still advise people to avoid or limit their use of this drug, especially if they start to develop any mental health symptoms or if they have relatives with psychotic illnesses." A 2007 study of studies published in the Lancet concluded that cannabis users are 40% more likely to be sufferers of a psychotic illness than non-users.
A large, unselected population-based study, published in British Journal of Psychiatry (2008), examined cannabis use and prodromal symptoms of psychosis at age 15–16 years and conclude that cannabis use is associated with prodromal symptoms of
psychosisPsychosis literally means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...
in adolescence.
The direction of causation was more directly examined in a study by Dr. Mikkel Arendt of Aarhus University in Risskov, Denmark, and colleagues, which found that individuals treated for psychotic episodes following cannabis use had the same likelihood of having a mother, sister or other "first-degree" relative with schizophrenia as did the individuals who had actually been treated for schizophrenia themselves. This suggests that the psychosis blamed on cannabis use is in fact the result of a genetic predisposition towards schizophrenia. "These people would have developed schizophrenia whether or not they used cannabis"
In a recent study at the Institute of Psychiatry at King's College London, scientists have confirmed a link between potent cannabis use (skunk cannabis, which accounts for 80 per cent of street seizures of the drug in the UK) and psychosis in healthy people. After testing 22 healthy males in their late 20s by injecting them with THC, with a control dummy injection administered to a percentage of the sample group, a link was found between the chemical and psychosis, "in which hallucinations leave sufferers unable to know what is real and what is imagined". Dr Paul Morrison, who lead the team, concluded, "these findings confirm that THC can induce a transient acute psychological reaction in psychiatrically well individuals". In addition, it was found that the extent of the psychotic reaction was not related to "the degree of anxiety or cognitive impairment" in the sample group. Further research is needed into the chemical makeup of skunk cannabis as it is believed stronger strains have virtually no traces of CBD (cannabidiol), which appears to counteract the damaging effects of THC.
The BEACH study (Bettering the Evaluation and Care of Health) conducted by the Australian General Practice Statistics and Classification Centre, based at the
University of SydneyThe University of Sydney is the oldest university in Australia. It was established in Sydney in 1850. It is a member of Australia's "Group of Eight" universities that are highly ranked in terms of their research performance...
, found that "cannabis smokers are more likely to suffer depression, anxiety and psychosis". The report continues that of the number of patients who mentioned cannabis use to their GP, 48% had a psychological problem, including 19% with depression, 9% with psychosis and 6% had anxiety. Much of the evidence for a short-lived cannabis psychosis is largely based on case reports where heavy cannabis use has preceded the onset of a psychotic episode, which then remits on abstinence. Depictions of a toxic or acute cannabis psychosis have been reported in a number of countries such as New Zealand, South Africa, Sweden and the UK.
The largest longitudinal study examining the link between cannabis and psychosis was undertaken by Andreasson and colleagues and followed 45,570 male
Swedish ArmyThe Swedish Army is the army branch of the Swedish Armed Forces, the military of Sweden.- Organization :The peace time organization of the Swedish Army is divided into a number of regiments for the different branches. The number of active regiments has been reduced since the end of the Cold War:-...
conscripts for 15 years. After controlling for other factors such as parental mental illness or a pre-exisiting psychotic illnes at conscription, the study found that the odds of developing schizophrenia later in life were "1.5 times higher for those who had used cannabis 1-10 times and 2.3 times more likely for those who had used cannabis 10 times or more". Further to criticism that the study did not control for he use of other potentially psychotogenic substances such as amphetamines, a follow-up study re-analysed the data and ruled out this argument, finding that cannabis use remained predictive of schizophrenia in a dose-dependent manner even after accounting for other substance use and pre-morbid social integration.
Research findings from the
University of MelbourneThe University of Melbourne is a public university located in Melbourne, Victoria. Founded in 1853, it is the second oldest university in Australia, and the oldest in Victoria...
and the [Orygen Research Centre], reported in
New Scientist reveal links between heavy cannabis use and brain size. In this study to determine whether long-term and heavy cannabis use is associated with gross anatomical abnormalities in two regions of the brain that are particularly rich in cannabinoid receptors, researchers found that the brain scans of 15 heavy users, who had smoked at least five joints a day for over 10 years, showed that on average the hippocampus and amygdales of the test group were 12% and 7.1% smaller than non-users, respectively. According to commentary provided by the
National Cannabis Prevention and Information CentreThe National Cannabis Prevention and Information Centre or NCPIC, is an Australian centre funded by the Commonwealth Department of Health and Ageing....
, these brain regions are intricately involved in learning and memory processes and are considered core components of the emotional brain and the research found that in addition left hippocampal and amygdala volume was inversely associated with cumulative doses of cannabis over the previous 10 years, as well as subthreshold positive psychotic symptoms. In their commentary, NCPIC state: "While modest use may not lead to significant neurotoxicity, these results corroborate similar findings within the animal literature and indicate that heavy daily cannabis use over protracted periods exerts harmful effects on brain tissue and mental health".
Co-occurrence of mental illness
A 2005 meta analysis of available data which evaluated several hypotheses regarding the correlation of cannabis and psychosis found that there is no support for the hypothesis that cannabis can cause cases of psychosis which would not have occurred otherwise, however further study is needed to explore the correlation between cannabis and other types of psychosis patients. Studies have shown that a risk does exist in some individuals with a predisposition to mental illness to develop symptoms of
psychosisPsychosis literally means abnormal condition of the mind, and is a generic psychiatric term for a mental state often described as involving a "loss of contact with reality"...
. The risk was found to be directly related to high dosage and frequency of use, early age of introduction to the drug, and was especially pronounced for those with a predisposition for mental illness. These results have been questioned as being biased by failing to account for medicinal versus recreational usage — critics contend it could be a causal relationship, or it could be that people who are susceptible to mental problems tend to smoke cannabis, or it could be connected to the criminalization of cannabis. Another important question is whether the observed symptoms of mental illness are actually connected to development of a permanent mental disorder; cannabis may trigger latent conditions, or be part of a complex coordination of causes of mental illness, referred to in
psychologyPsychology is an academic and applied discipline involving the systematic, and sometimes scientific, study of human or animal mental functions and behavior...
as the
diathesis-stress modelThe diathesis–stress model is a psychological theory that explains behavior as both a result of biological and genetic factors , and life experiences . This model thus assumes that a disposition towards a certain disorder may result from a combination of one's genetics and early learning...
. People with developed psychological disorders are known to self-medicate their symptoms with cannabis as well, although one study has claimed that those with a predisposition for psychosis did not show a statistically significant increase in likelihood of cannabis use four years later.
A 2005 literature review of the use of cannabis in mental health patients found that the drug can have very different effects on different patients. Although "no controlled trials of THC have been done in bipolar disorder," there is anecdotal evidence that "for some people marijuana is beneficial" as a treatment for bipolar disorder. The reviewers suggested that randomized studies and standardized administration techniques would be required to create conclusive evidence.
Correlation versus causality
Some studies conclude that there is a
correlation of cannabis use and some symptoms of psychosis, but don't necessarily support the notion that cannabis use is a sufficient or necessary
cause for psychosis. It might be a component cause, part of a complex constellation of factors leading to psychosis, or it might be a correlation without forward causality at all.
For example, a review of the evidence by Louise Arsenault, et al., in 2004 reports that on an individual level, cannabis use confers an overall twofold increase in the relative risk of later schizophrenia, assuming a causal relationship. This same research also states that "There is little dispute that cannabis intoxication can lead to acute transient psychotic episodes in some individuals". The study synthesizes the results of several studies into a statistical model. The study does not correct for the use of other illicit drugs, and relies on self-reporting of cannabis dosage. The study also does not determine if the cannabis use preceded or followed the mental health problem.
Similarly, the landmark study, in 1987, of 50,000 Swedish Army conscripts, mentioned earlier, found that those who admitted at age 18 to having taken cannabis on more than 50 occasions, were six times more likely to develop schizophrenia in the following 15 years. In fact, psychosis cases were restricted to patients requiring a hospital admission. These findings have not been replicated in another population based sample. As the study did not control for symptoms preexisting onset of cannabis use, the use of other illicit drugs, the study does not resolve the
correlation versus causality question but has fueled a major debate within the scientific community. This study also used self reporting for cannabis dosage.
A 2005 study found that "the onset of schizotypal symptoms generally precedes the onset of cannabis use. The findings do not support a causal link between cannabis use and schizotypal traits". It should be noted that a
schizotypal personality disorderSchizotypal personality disorder, or simply schizotypal disorder, is a personality disorder that is characterized by a need for social isolation, odd behavior and thinking, and often unconventional beliefs.-History:...
is a
personality disorderPersonality disorders, formerly referred to as character disorders, are a class of personality types which deviate from the contemporary expectations of a society....
different from schizophrenia. A 2007 British study concluded, "We found few appreciable differences in symptomatology between schizophrenic patients who were or were not cannabis users. There were no differences in the proportion of people with a positive family history of schizophrenia between cannabis users and non-users. This argues against a distinct schizophrenia-like psychosis caused by cannabis."
Research based on the
Dunedin Multidisciplinary Health and Development StudyThe Dunedin Multidisciplinary Health and Development Study is a long-running cohort study of 1037 people born over the course of a year in Dunedin, New Zealand....
has found that those who begin regular use of cannabis in early adolescence (from age 15,
medianIn probability theory and statistics, a median is described as the number separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to highest...
25 days per year by age 18) and also fit a certain
geneticGenetics, , a discipline of biology, is the science of heredity and variation in living organisms. The fact that living things inherit traits from their parents has been used since prehistoric times to improve crop plants and animals through selective breeding...
profile (specifically, the Val/Val variant of the COMT gene) are five times more likely to develop psychotic illnesses than individuals with differing genotypes, or those who do not use cannabis. The study was noted for having controlled for preexisting symptoms, but is open to the criticism that it cannot control for late adolescent onset of psychotic illness. Also, the study was on a
cohort populationA cohort study or panel study is a form of longitudinal study used in medicine, social science and ecology. It is one type of study design and should be compared with a cross-sectional study....
, so there is no way to correlate a change in the
rate of adolescent use with a change in the
rate of incidence of schizophrenia in the study population. These points undermine its value in resolving the
correlation versus causality question.
A study that inversely correlated cerebrospinal anandamide (an endogenous cannabinoid) levels with severity of schizophrenia (i.e., that anandamide was released in order to suppress psychosis) suggests that cannabis use may be an effect of schizophrenia or its predisposition, as opposed to a cause.
The fact that the prevalence of cannabis use has increased substantially during the last decades whereas the prevalence of psychotic illness has not suggests no causal relationship.
Cannabidiol and schizoprenia
A recent study has shown that
cannabidiolCannabidiol is a psychoactive cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.CBD alone is not intoxicating, but displayed sedative effects in animal tests...
(a major constituent of cannabis) may be as effective as atypical antipsychotics in treating schizophrenia, Further research has verified these results. Leweke et al., (2009) performed a double blind, 4 week, explorative study controlled clinical trial, to compare the effects of purified cannabidiol and the atypical antipsychotic
amisulprideAmisulpride , is a psychoactive drug that is used as an atypical antipsychotic and antidepressant. It was introduced by Sanofi-Aventis in the 1990s.- Pharmacology :...
on improving the symptoms of schizophrenia in 42 patients with acute schizophrenia. 'Both treatments were associated with a significant decrease of psychotic symptoms after 2 and 4 weeks as assessed by BPRS and PANSS. However, there was no statistical difference between both treatment groups. In contrast, cannabidiol induced significantly less side effects (EPS, increase in prolactin, weight gain) when compared to amisulpride'. The authors conclude cannabidiol revealed subtantial antipsychotic properties in acute paranoid schizophirenia (Leweke et. al, 2009). This led the authors to suggest the
endocannabinoid systemThe endocannabinoid system refers to a group of neuromodulatory lipids and their receptors that are involved in a variety of physiological processes including appetite, pain-sensation, mood, and memory...
plays an adaptive role in the development of paranoid schizophirenia and that this reasearch provides evidence that this mechanism may be a valuable target for 'antipsychotic treament strategies' .
Smoking
The process most popularly used to ingest cannabis is smoking, and for this reason most research has evaluated health effects from this method of ingestion. Other methods of ingestion may have lower or higher health risks. See section on harm reduction below for more information on other methods of ingestion. Tobacco smoking has well-established risks such as
bronchitisAcute bronchitis is an inflammation of the large bronchi in the lungs that is usually caused by viruses or bacteria and may last several days or weeks. Characteristic symptoms include cough, sputum production, and shortness of breath and wheezing related to the obstruction of the inflamed airways...
,
coughA cough , in medicine, is a sudden and often repetitively occurring defense reflex which helps to clear the large breathing passages from excess secretions, irritants, foreign particles and microbes...
ing, overproduction of
mucusIn vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. It is a viscous colloid containing antiseptic enzymes and immunoglobulins that serves to protect epithelial cells in the respiratory,...
, wheezing, and
addictionThe term "addiction" is used in many contexts to describe an obsession, compulsion, or excessive psychological dependence, such as: drug addiction The term "addiction" is used in many contexts to describe an obsession, compulsion, or excessive psychological dependence, such as: drug addiction The...
. Similar risks for smoking cannabis related to airway
inflammationInflammation is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue. Inflammation is not a...
have been suggested in a study of healthy cannabis users who exhibited similar early characteristics to
tobacco smoking Tobacco smoking is the practice where tobacco is burned and the vapors either tasted or inhaled. The practice began as early as 5000–3000 BC. Many civilizations burnt incense during religious rituals, which was later adopted for pleasure or as a social tool. Tobacco was introduced to the old world...
.
The effects of tobacco and cannabis smoking differ, however, as they affect different parts of the
respiratory tractIn humans the respiratory tract is the part of the anatomy that has to do with the process of respiration.The respiratory tract is divided into 3 segments:*Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx...
: whereas tobacco tends to penetrate to the smaller, peripheral passageways of the lungs, cannabis tends to concentrate on the larger, central passageways. One consequence of this is that cannabis, unlike tobacco, does not appear to cause
emphysemaEmphysema is a lung disease, characterized by an abnormal, permanent enlargement of air spaces distal to the terminal bronchioles. The disease is coupled with the destruction of walls, but without obvious fibrosis...
, though this claim is disputed. A 2002 report by the
British Lung FoundationThe British Lung Foundation is a British charity dedicated to promoting lung health and supporting those affected by lung disease.- About the British Lung Foundation :...
estimated that three to four cannabis cigarettes a day were associated with the same amount of damage to the lungs as 20 or more tobacco cigarettes a day. Unlike tobacco, regular cannabis use does not appear to cause chronic obstructive pulmonary disease.
It is important to note that, in some cases, cannabis users mix commercial tobacco in
jointsJoint is slang for a cigarette rolled using cannabis. Rolling papers are the most common rolling medium among industrialized countries, however brown paper, cigarettes with the tobacco removed, and newspaper are commonly used throughout the developing world. Modern papers are now commonly made...
, called "Spliff" (popular in
EuropeEurope is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
), tobacco mixed with hash in a
chillumA chillum, or chilam, is a pipe used by Indian Sadhu holy men, Rastafarians and by many recreational drug users to smoke cannabis, opium, tobacco, etc. The chillum is a conical pipe which has been used since at least the 18th century as pipes by Sadhus in India to imbibe cannabis...
(
IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
), or cannabis rolled in tobacco leaves (a
bluntA blunt is a cigar which is wider than a cigarillo and not quite as wide as a Corona. These cigars typically consist of two main parts; the inner leaf, which is similar to a cigarette rolling paper, except it is made of tobacco, and a thicker outer leaf which is rolled around the inner leaf in a...
), which would expose the user to the additional risks of tobacco, such as rapid physical addiction to
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
.
Cancer risk
Cannabis smoke contains numerous
carcinogenA carcinogen is any substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the increase of its propagation. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...
s. Surprisingly, an extensive study published in 2006 by Donald Tashkin of the
University of California, Los AngelesThe University of California, Los Angeles is a research university located in the Westwood neighborhood of Los Angeles, California, in the United States. It was founded in 1919 and is the second-oldest general-purpose campus in the University of California system...
found that there is no significant link between smoking cannabis and lung cancer. The study, which involved a large population sample (1,200 people with lung, neck, or head cancer, and a matching group of 1,040 without cancer) found no correlation between marijuana smoking and increased
lung cancerLung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells...
risk. The results indicated no correlation between long and short-term cannabis use and cancer, indicating a possible therapeutic effect. Extensive cellular studies and some studies in animal models suggest that THC or
cannabidiolCannabidiol is a psychoactive cannabinoid found in Cannabis. It is a major constituent of the plant, representing up to 40% in its extracts.CBD alone is not intoxicating, but displayed sedative effects in animal tests...
has antitumor properties, either by encouraging
programmed cell deathProgrammed cell-death is death of a cell in any form, mediated by an intracellular program. In contrast to necrosis, which is a form of cell-death that results from acute tissue injury and provokes an inflammatory response, PCD is carried out in a regulated process which generally confers...
of genetically damaged cells that can become cancerous, or by restricting the development of the blood supply that feeds tumors, or both.
In 2008 a smaller study was released by the Medical Research Institute of New Zealand suggested that smoking cannabis increased the risk of lung cancer by 5.7 times over non-smokers. The small 79 person study noted that "In the near future we may see an 'epidemic' of lung cancers connected with this new carcinogen. And the future risk probably applies to many other countries, where increasing use of cannabis among young adults and adolescents is becoming a major public health problem."
Prior, a 1997 study examining the records of 64,855 Kaiser patients (14,033 of whom identified themselves as current smokers), also found no positive correlation between cannabis use and cancer.
A
Research Triangle InstituteThe Research Triangle Institute is a non-profit research organization based in the Research Triangle Park of North Carolina. RTI is the oldest tenant of this major research park, and the sister organization to the Research Triangle Foundation. RTI has over 2,600 employees engaged in many...
study concluded that THC, a dilative agent (
bronchodilatorA bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing airway resistance and thereby facilitating airflow. Bronchodilators may be endogenous , or they may be medications administered for the treatment of breathing difficulties...
), may help cleanse the lungs by dilating the bronchi, and could actively reduce the instance of tumors. Additionally, a study by Rosenblatt
et al. found no association between marijuana use and the development of
head and neck squamous cell carcinomaThe term head and neck cancer refers to a group of biologically similar cancers originating from the upper aerodigestive tract, including the lip, oral cavity , nasal cavity, paranasal sinuses, pharynx, and larynx. Most head and neck cancers are squamous cell carcinomas, originating from the...
. However, a contrasting study conducted in 2000 linked the smoking of cannabis to the growth of cancerous tumors through the impairment of anti-tumor defenses.
A 2009 study found that cannabis use may increase the risk of
testicular cancerTesticular cancer is cancer that develops in the testicles, a part of the male reproductive system.In the United States, between 7,500 and 8,000 diagnoses of testicular cancer are made each year. Over his lifetime, a man's risk of testicular cancer is roughly 1 in 250 . It is most common among...
. In particular, the risk of developing nonseminoma testicular cancer, a more aggressive form of the disease, was increased in current cannabis users and even greater in long-term chronic users. This however is overshadowed by the fact that researchers are unable to determine what about marijuana causes the increased risk, or for that matter if a positive correlation can be established. A statement was released by the researchers that performed the study as seen below:
"This is the first study to look at this question, and by itself is not definitive. And there's a lot more research that would have to be done in order to prove that marijuana use really increases a man's risk of developing testicular cancer," - Stephen Schwartz.
Cannabis smoke (but not the plant itself) has recently been added to a "list of substances California regulators say cause cancer". California's Office of Environmental Health Hazard assessment has added cannabis smoke to the list after it found that it "contains 33 of the same harmful chemicals as tobacco smoke."
UCLA study
On 23 May 2006,
Donald Tashkin, M.D., Professor of Medicine at the David Geffen School of Medicine at UCLA in Los Angeles announced that the use of cannabis does not appear to increase the risk of developing lung cancer, or increase the risk of head and neck cancers, such as cancer of the tongue, mouth, throat, or esophagus. The study involved 2252 participants, with some of the most chronic marijuana smokers having smoked over 22,000 marijuana cigarettes. The finding of Donald Tashkin, M.D., and his team of researchers in 2006 refined their earlier studies published in a Dec. 17th 2000 edition of the peer-reviewed journal Cancer Epidemiology Biomarker and Prevention. Many opponents of marijuana incorrectly cite the original finding of UCLA Medical Center from 2000 as "proof" that marijuana leaves the users at higher risk for cancer of the lung, and cancerous tumors, even though the researchers at the UCLA Medical Center have revised their finding with a more in-depth study on the effects of the use of marijuana. This seemed to contradict assumptions made after some studies, like those from Dale Geirringer et al., which found that 118 carcinogens were produced when marijuana underwent combustion, and two carcinogens {2-Methyl-2, 4(2H-1-benzopyran-5-ol) & 5-[Acetyl benz[e]azulene-3,8-dione} formed when marijuana underwent vaporization with the
Volcano VaporizerThe Volcano Vaporizer is a vaporizer machine consisting of a conical heater base with controls for manipulating the airflow and temperature. It is used for aromatherapy, smokeless ingestion of cannabis or other herbs, and culinary preparation. The air collection system consists of a heatproof bag,...
. To help explain this seemingly chemical proof of carcinogenity inherent in the process of combustion, Tashkin noted that "one possible explanation for the new findings, he said, is that THC, a chemical in marijuana smoke, may encourage aging cells to die earlier and therefore be less likely to undergo cancerous transformation."
In a study of ten smokers with mild respiratory issues Hii et al. found evidence of lung disease in the form of severe bullae (fluid-filled, thin-walled blisters) of different shapes and sizes. Despite such lung disease, the patients chest x-rays were normal and lung function was only mildly reduced in nearly half of the patients. The cannabis-smoking patient group was, on average, 41 years old—considerably younger than previously research tobacco-smoking patients with lung disease, who had an average age of between 62–67 years. The researchers conclude that the younger age of lung disease and poorer lung function may be due to different smoking patterns demonstrated in cannabis smokers, who have been found to inhale larger amounts of smoke, which is held in the lungs for longer periods of time.
Reducing health risks
The health consequences of cannabis use may vary depending on method of use. Proposed safer alternatives include:
- Filtered cigarettes (see below).
- Vaporizer
A vaporizer is a device used to extract and deliver via inhalation the active ingredients of plant material, commonly cannabis, tobacco, or any of many other herbs or blends . Vaporization is an alternative to smoking...
s (see above), devices for inhaling THC without burning the cannabis; top temperature 210°C (410°F) compared to 815°C (1500°F) in a burning cigarette.
- Electronic cigarette; contains rechargeable battery and a heating element which vaporizes, in most brands, liquid nicotine from a cartridge; cannabinol (honey oil
Honey oil is a specific type of hash oil produced by some solvents, most commonly butane, and isopropanol. Sometimes called butane hash oil or BHO , or simply "oil", it is traditionally a dark viscous liquid made by solvent extraction of cannabis resin...
) would be loaded into the cartridge instead of nicotine, providing benefits to cannabis users at low initial cost.
- Long-stemmed one-hitters or "semi-vaporization" utensils provide 25 mg servings in a 1/4" or 6-mm-inner-diameter screened crater. This minimizes carbon monoxide intake and eliminates side-stream smoke.
- Eating cannabis brownie
Cannabis foods concerns the preparation and cooking of foods with the drug cannabis in herbal or resin form as an alternate way to experience the effects of the drug without smoking it. Commonly it is cooked into a cake, cookie, brownie, or other baked product to be distributed socially. There are...
s or other foods containing cannabutter, budderBudder is a concentrated form of THC, the main psychoactive chemical in cannabis .- Comparison with other cannabis-related drugs :...
or THCThe acronym THC has several possible meanings:* Tetrahydrocannabinol, the main active chemical compound in Cannabis* Toronto Hemp Company, the world's largest Hemp and Cannabis Culture store, located in Toronto, Canada....
. Consuming cannabis edibles is by far the safest method, as the respiratory system is unaffected and is highly unlikely to harm the stomach.
- Bong
For the Dinosaur Jr. song "The Lung", see You're Living All Over MeA bong, also commonly known as a water pipe, is a smoking device, generally used to smoke cannabis, tobacco, or other substances. The construction of a bong and its principle of action is similar to that of the hookah...
s: specialized pipes filtering, often cooling and sometimes diffusing smoke through water. However, evidence suggests that use of water pipes proportionally filters out higher concentrations of THC as well. Therefore, waterpipe users need to inhale more carcinogenic smoke to get equal amounts of THC as, say, with an unfiltered joint.
- High potency cannabis and cannabis extracts, such as hashish
Hashish is a preparation of cannabis composed of the compressed stalked resin glands called trichomes, collected from the cannabis plant. It contains the same active ingredients but in higher concentrations than other parts of the plant such as the buds or the leaves...
or honey oilHoney oil is a specific type of hash oil produced by some solvents, most commonly butane, and isopropanol. Sometimes called butane hash oil or BHO , or simply "oil", it is traditionally a dark viscous liquid made by solvent extraction of cannabis resin...
, allowing the absorption of the same amount of cannabinoids while inhaling less smoke.
- Bleach- and glue-free papers such as Aleda and RAW
RAW is a brand of cigarette rolling paper used in the process of RYO . It contains a "proprietary" blend of vegan unbleached fibers, resulting in a thin, brown translucent paper...
.
Like all smoke, cannabis smoke contains tars which, unlike cannabinoids themselves, are rich in carcinogenic polycyclic aromatic hydrocarbons, a prime culprit in smoking-related cancers.
Vaporizers, by heating the cannabis active constituents and aromatic substances to be inhaled without combustion of the preparation, almost exclude the risk altogether. A 2000
study conducted by NORML and MAPS found that the two tested vaporizers delivered significantly fewer carcinogens than a cigarette.
Behavioral effects
Government studies often point to statistical data accumulated by methods like the National Household Survey on Drug Abuse (NHSDA), the
Monitoring the FutureMonitoring the Future is an annual survey given to 50,000 8th, 10th and 12th graders in the United States to determine drug use trends and patterns, including scales measuring behaviors, attitudes, and values. The survey started in 1975, with 12th graders. It was expanded in 1991 to include 8th...
study (MTF), and the
Arrestee Drug Abuse MonitoringArrestee Drug Abuse Monitoring, or ADAM, was a survey conducted by the U.S. Department of Justice to gauge the prevalence of alcohol and illegal drug use among prior arrestees...
(ADAM) program, which claim lower school averages and higher
dropout-In science:*Dropout .*Dropout .*Dropout .*Dropout as a type of sampling bias in scientific studies-Popular culture:*The Drop-out a 2010 upcoming film starring Cher and Johnny Knoxville....
rates among users than nonusers. However, the major contributor to a lack of credibility in these studies, is that in many cases, like with NHSDA and MTF, these surveys are usually self-administered and may be anonymous. The likeliness of over or under representing data definitely undermines the effectiveness of these instruments. The ADAM study is conducted anonymously, but only seeks information from a sample of people who have been arrested for drug-related offenses. Socially deviant behavior may be found more frequently in individuals of the criminal justice system compared to those in the general population, including non users. In response, independent studies of college students have shown that there was no difference in grade point average, and achievement, between marijuana users and nonusers, but the users had a little more difficulty deciding on career goals, and a smaller number were seeking advanced professional degrees. Laboratory studies of the relationship between motivation and marijuana outside of the classroom, where volunteers worked on operant tasks for a wage representing a working world model, also fail to distinguish a noticeable difference between users and non users.
A USC study of 4,400 Internet users found that "adults apparently do not increase their risk for depression by using marijuana", and in fact show less self-reported symptoms of depression.
Gateway drug hypothesis
The
gateway drugThe gateway drug theory is the hypothesis that the habitual use of less deleterious drugs may lead to a future risk of using more dangerous hard drugs and crime....
hypothesis asserts that the use of cannabis may ultimately lead to the use of harder drugs. For the most part, it was commonly thought that cannabis gateways to other drugs because of
socialSociology is the scientific or systematic study of human societies. It is a branch of social science that uses various methods of empirical investigation and critical analysis to develop and refine a body of knowledge about human social structure and activity, often with the goal of applying such...
factors. For example, the
criminalizationCriminalization or criminalisation, in criminology, is "the process by which behaviors and individuals are transformed into crime and criminals". Previously legal acts may be transformed into crimes by legislation or judicial decision...
of cannabis in many countries associates its users with
organized crimeOrganized crime or criminal organizations can be defined as a transnational grouping of highly centralized enterprises run by criminals for the purpose of engaging in illegal activity, most commonly for the purpose of generating a monetary profit...
promoting the
illegal drug tradeThe illegal drug trade is a global black market consisting of the cultivation, manufacture, distribution and sale of illegal controlled drugs. Most jurisdictions prohibit trade, except under license, of many types of drugs by drug control laws...
.
A July 2006 study by Ellgren
et al. strictly tested lab rats for the biological mechanism of the gateway drug effect. The study administered 6 "
teenageAdolescence Adolescence Adolescence (lat adolescere, (to grow) is a transitional stage of physical and mental human development that occurs between childhood and adulthood. This transition involves biological (i.e. pubertal), social, and psychological changes, though the biological or...
" (28 and 49 days old) rats delta-9-tetrahydrocannabinol, and 6 were the
controlWhen an experiment is being conducted to investigate the effect of a single variable of interest on a particular system, a scientific control is used to minimize unintended influences on that system. Such unintended influences include researcher bias, environmental changes, and biological variation...
. One week after the first part was completed, catheters were inserted in the
jugular veinThe jugular veins are veins that bring deoxygenated blood from the head back to the heart via the superior vena cava.-Internal and external:There are two sets of jugular veins: external and internal....
of all of the adult rats and they were able to self-administer themselves
heroinHeroin, or diacetylmorphine , also known as diamorphine , is a semi-synthetic opioid drug synthesized from morphine, a derivative of the opium poppy. It is the 3,6-diacetyl ester of morphine...
by pushing a lever. The study found that initially both groups behaved the same and began to self-administer heroin frequently, but then stabilized at different levels. The rats that had previously been administered THC consumed about 1.5 times more heroin than those that had not. Because many THC receptors interact with the opioid system, the study surmised that adolescent cannabis use overstimulates and alters the pleasure and reward structures of the brain, thus increasing the already high risk of addiction for people who start to use heroin. However, the rats took up self-administration at the same rate regardless of adolescent THC exposure, and observed levels of "drug-seeking behavior" were also the same.
PsychopharmacologistPsychopharmacology is the study of drug-induced changes in mood, sensation, thinking, and behavior....
Ian Stolerman, from
King's College LondonKing's College London is a British higher education institution and co-founding constituent college of the University of London. Founded by King George IV and the Duke of Wellington in 1829, its royal charter is predated, in England, only by those of the Universities of Oxford and Cambridge...
, finds the biological cannabis gateway drug effect "somewhat preliminary", and states "it's too early to say there's a consensus, but a small number of studies like this suggest that there is a physiological basis for this effect." Other drugs, he notes, such as cocaine and amphetamines are involved in another brain pathway called the dopaminergic system. Cells in that system also interact with THC receptors and could be modified by cannabis exposure. Cannabinoid receptors are 10 times more prevalent in the brain than opioid receptors. According to Dr. Hurd, one of the study leaders, two other drugs that also stimulate opioid cells, and could therefore also feasibly cause a gateway effect, are
nicotineNicotine is an alkaloid found in the nightshade family of plants which constitutes approximately 0.6–3.0% of dry weight of tobacco, with biosynthesis taking place in the roots, and accumulating in the leaves...
and alcohol.
However, a December 2006 study by the
American Psychiatric AssociationThe American Psychiatric Association is the main professional organization of psychiatrists and trainee psychiatrists in the United States, and the most influential worldwide. Its some 38,000 members are mainly American but some are international...
challenges these findings. A 12 year study on 214 boys from ages 10–12 showed that adolescents who used marijuana prior to using other drugs, including alcohol and tobacco, were no more likely to develop a substance abuse disorder than other subjects in the study. "This evidence supports what's known as the common liability model ... states the likelihood that someone will transition to the use of illegal drugs is determined not by the preceding use of a particular drug, but instead by the user's individual tendencies and environmental circumstances," investigators stated in a press release. They added, "The emphasis on the drugs themselves, rather than other, more important factors that shape a person's behavior, has been detrimental to drug policy and prevention programs."
Models used in a 2002 study by
RANDThe RAND Corporation is a nonprofit global policy think tank first formed to offer research and analysis to the United States armed forces by Douglas Aircraft Company and currently financed predominantly by the U.S. government, a private endowment, predominantly pharmaceutical corporations,...
cast doubt on the gateway effect and show "that the marijuana gateway effect is not the best explanation for the link between marijuana use and the use of harder drugs," as noted by Andrew Morral, associate director of RAND's Public Safety and Justice unit and lead author of the study.
Memory and intelligence
A 2002
longitudinal studyA longitudinal study is a correlational research study that involves repeated observations of the same items over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the life...
published in the
Canadian Medical Association JournalThe Canadian Medical Association Journal is a general medical journal that is published biweekly by the Canadian Medical Association . It showcases innovative research and ideas aimed at improving health for people in Canada and globally...
concluded that "marijuana does not have a long-term negative impact on global intelligence", and that "current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week." In fact, current light users and former users showed larger IQ gains than those who had never used cannabis.
A 2008 study suggests that long-term, heavy cannabis use (over five joints daily for more than ten years) are associated with structural abnormalities in the hippocampus and amygdala areas of the brain. The hippocampus, thought to regulate emotion and memory, and the amygdala, involved with fear and aggression, tended to be smaller in heavy and long term cannabis users than in controls (volume was reduced by an average of 12 percent in the hippocampus and 7.1 percent in the amygdala). The study concluded that "heavy daily cannabis use across protracted periods exerts harmful effects on brain tissue and mental health."
A 2002 study published in
NeurologyNeurology is a scientific journal published by the American Academy of Neurology....
concluded that "very heavy use of marijuana is associated with persistent decrements in neurocognitive performance even after 28 days of abstinence."
The strongest evidence regarding cannabis and memory focuses on its short-term negative effects on short-term and working memory. Evidence also suggests that long-term effects exist, but these appear to be reversible except possibly in very heavy users.
A 1998
Journal of Neuroscience in vitroA procedure performed in vitro is performed not in a living organism but in a controlled environment, such as in a test tube or Petri dish...
research, which was carried out on hippocampal cells excised from decapitated rats, using THC carried in ethanol to saturate the neurons, suggests that THC is toxic for cultured hippocampal neurons.
A 1998 report by INSERM and CNRS, which was directed by Dr. Pierre-Bernard Roques, determined that, "former results suggesting anatomic changes in the brain of chronic cannabis users, measured by tomography, were not confirmed by the accurate modern
neuro-imaging techniquesNeuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
(such as MRI) ... Moreover, morphological impairment of the hippocampus [which plays a part in memory and navigation] of rat after administration of very high doses of THC was not shown."
Legal and political constraints on open research
In many countries, experimental science regarding cannabis is restricted due to its
illegalitySince the 20th century, most countries have enacted laws affecting the legality of cannabis regarding the cultivation, use, possession, or transfer of cannabis for recreational use. Many jurisdictions have lessened the penalties for possession of small quantities of cannabis, so that it is punished...
. Thus, cannabis as a drug is often hard to fit into the structural confines of medical research because appropriate, research-grade samples are difficult to obtain for research purposes, unless granted under authority of national governments.
United States
This issue was recently highlighted in the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
by the clash between
Multidisciplinary Association for Psychedelic StudiesThe Multidisciplinary Association for Psychedelic Studies is a U.S.-based non-profit organization that assists scientists to design, fund, obtain approval for and report on studies into the risks and benefits of psychedelic drugs...
(MAPS), an independent research group, and the
National Institute on Drug AbuseThe National Institute on Drug Abuse is a United States federal-government research institute whose mission is to "lead the Nation in bringing the power of science to bear on drug abuse and addiction."-History:...
(NIDA), a
federal agencyThe federal government of the United States is the central government entity established by the United States Constitution, which shares sovereignty over the United States with the governments of the individual U.S. states. The federal government has three branches: the legislative, executive, and...
charged with the application of science to the study of drug abuse. The NIDA largely operates under the general control of the
Office of National Drug Control PolicyThe White House Office of National Drug Control Policy , a former cabinet level component of the Executive Office of the President of the United States, was established in 1988 by the Anti-Drug Abuse Act...
(ONDCP), a
White House officeThe Executive Office of the President consists of the immediate staff of the President of the United States, as well as multiple levels of support staff reporting to the President. The EOP is headed by the White House Chief of Staff, currently Rahm Emanuel.-History:In 1939, during Franklin D...
responsible for the direct coordination of all legal, legislative, scientific, social and political aspects of federal drug control policy.
The cannabis that is available for research studies in the United States is grown at the
University of MississippiThe University of Mississippi, also known as Ole Miss, is a public, coeducational research university located in Oxford, Mississippi. Founded in 1848, the school is composed of the main campus in Oxford and three branch campuses located in Booneville, Tupelo, and Southaven...
and solely controlled by the NIDA, which has veto power over the
Food and Drug AdministrationThe Food and Drug Administration is a Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, tobacco products, dietary supplements, Medication drugs, vaccines, Biopharmaceutical, blood transfusion,...
(FDA) to define accepted protocols. Since 1942, when cannabis was removed from the U.S. Pharmacopoeia and its medical use was prohibited, there have been no legal (under federal law) privately funded cannabis production projects. This has resulted in a limited amount of research being done and possibly in NIDA producing cannabis which has been alleged to be of very low potency and inferior quality.
MAPS, in conjunction with Professor
Lyle CrakerLyle E. Craker is a Professor in the Department of Plant, Soil and Insect Sciences at the University of Massachusetts. Since 2005, Craker has been trying to obtain a permit from the United States Drug Enforcement Administration to grow marijuana for research purposes.-Education:In 1963, Craker...
, PhD, the director of the Medicinal Plant Program of the University of Massachusetts at Amherst, sought to provide independently grown cannabis of more appropriate research quality for FDA-approved research studies, and encountered opposition by NIDA, the ONDCP, and the U.S.
Drug Enforcement AdministrationThe Drug Enforcement Administration is a federal law enforcement agency under the United States Department of Justice, tasked with combating drug smuggling and use within the U.S...
(DEA).
United Kingdom
In countries such as the United Kingdom a license for growing cannabis is required if it is to be used for botanical or scientific reasons. It is referred to as a "controlled drug". In such countries a greater depth and variety of scientific research has been performed. Recently several habitual smokers were invited to partake in various tests by British medical companies in order for the UK government to ascertain the influence of cannabis on operating a motor vehicle.
Pathogens and microtoxins
Most
microorganismA microorganism or microbe is an organism that is microscopic...
s found in cannabis only affect plants and not humans, but some microorganisms, especially those that proliferate when the herb is not correctly dried and stored, can be harmful to humans. Some users may store marijuana it in an airtight bag or jar in a
refrigeratorA refrigerator is a cooling appliance comprising a thermally insulated compartment and a heat pump—chemical or mechanical means—to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which spoil...
to prevent fungi and bacterial growth.
Fungi
The fungi
Aspergillus flavusAspergillus flavus is a fungus. It is a common mold in the environment, and can cause storage problems in stored grains. It can also be a human pathogen, associated with aspergillosis of the lungs and sometimes causing corneal, otomycotic, and nasoorbital infections. Many strains produce...
,
Aspergillus fumigatusAspergillus fumigatus is a fungus of the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in immuno-compromised individuals....
,
Aspergillus nigerAspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food...
,
Aspergillus parasiticusAspergillus parasiticus is a mold known to produce aflatoxin, although strains of it exist that do not produce this carcinogen. It is sometimes found on black olives....
,
Aspergillus tamarii,
Aspergillus sulphureus,
Aspergillus repens,
Mucor hiemalisMucor hiemalis is a fungal plant pathogen.Morphology and cell structure: M. hiemalis grows in expanding gray colonies. It grows branched sporangiophores that yielding yellow to dark brown sporangia which can mate to form black-brown, spiny zygospores.Physiology: M. hiemalis is nitrate positive and...
(not a human pathogen),
Penicillin chrysogenum,
Penicillin italicum and
Rhizopus nigrans have been found in moldy cannabis.
AspergillusAspergillus is a genus of a few hundred molds found throughout much of nature worldwide. Aspergillus was first catalogued in 1729 by the Italian priest and biologist Pier Antonio Micheli. Viewing the fungi under a microscope, Micheli was reminded of the shape of an aspergillum , and named the genus...
mold species can infect the lungs via smoking or handling of infected cannabis and cause opportunistic and sometimes deadly
AspergillosisAspergillosis is the name given to a wide variety of diseases caused by fungi of the genus Aspergillus. The most common forms are allergic bronchopulmonary aspergillosis, pulmonary aspergilloma and invasive aspergillosis. Most humans inhale Aspergillus spores every day...
. Some of the microorganisms found create
aflatoxinAflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, most notably Aspergillus flavus and Aspergillus parasiticus. Aflatoxins are toxic and among the most carcinogenic substances known...
s, which are toxic and carcinogenic. Researchers suggest that moldy cannabis thus be discarded.
Mold is also found in smoke from mold infected cannabis, and the lungs and nasal passages are a major means of contracting fungal infections. "Levitz and Diamond (1991) suggested baking marijuana in home ovens at 150 °C [302 °F], for five minutes before smoking. Oven treatment killed conidia of A. fumigatus, A. flavus and A. niger, and did not degrade the active component of marijuana, tetrahydrocannabinol (THC)."
Bacteria
Cannabis contaminated with
Salmonella muenchen was positively
correlatedIn statistics, correlation indicates the strength and direction of a relationship between two random variables. The commonest use refers to a linear relationship. In general statistical usage, correlation or co-relation refers to the departure of two random variables from independence...
with dozens of cases of
salmonellosisSalmonellosis is an infection with Salmonella bacteria. Most persons infected with Salmonella develop diarrhea, fever, vomiting, and abdominal cramps, 12 to 72 hours after infection. In most cases, the illness lasts 3 to 7 days; most affected persons recover without treatment...
in 1981. "Thermophilic actinomycetes" were also found in cannabis.
See also
- Contact high
Contact high is a phenomenon that sometimes occurs in people and animals who come into contact with someone who is under the influence of drugs. It involves a supposed transfer of the psychological state of highness. This is often attributed to things such as stale latent cannabis smoke and...
- Harm reduction
Harm reduction, or harm minimisation, refers to a range of pragmatic and evidence-based public health policies designed to reduce the harmful consequences associated with drug use and other high risk activities ....
- Health effects of tobacco smoking
The health effects of tobacco are the circumstances, mechanisms, and factors of tobacco consumption on human health. Epidemiological research have been focused primarily on tobacco smoking, which has been studied more extensively than any other form of consumption.Tobacco use leads most commonly to...
- Medical cannabis
Medical cannabis refers to the use of the dried flowers and subtending leafs and stems from pistillate Cannabis plants as a physician-recommended drug or herbal therapy....
- National Cannabis Prevention and Information Centre
The National Cannabis Prevention and Information Centre or NCPIC, is an Australian centre funded by the Commonwealth Department of Health and Ageing....
- Psychoactive drug
A psychoactive drug, psychopharmaceutical or psychotropic substance is a chemical substance that acts primarily upon the central nervous system where it alters brain function, resulting in changes in perception, mood, consciousness and behavior...
- Responsible drug use
Responsible drug use is a harm reduction strategy which argues that people can use drugs, with reduced or eliminated risk of negatively affecting other parts of their lives or those of others...
- Tradable smoking pollution permits
Tradable smoking pollution permits were proposed by the economists Robert Haveman and John Mullahy of the University of Wisconsin–Madison. as an alternative to smoking bans to solve the problem of cigarette-smoking "externalities" in public bars and restaurants...
External links
- How marijuana works from HowStuffWorks
- Microbiological contaminants of marijuana
- Cannabis Use and Psychosis from National Drug and Alcohol Research Centre, Australia
- The key research on cannabis use and mental illness at BBC News
- Provision of Marijuana and Other Compounds For Scientific Research recommendations of The National Institute on Drug Abuse National Advisory Council
- Scientific American Magazine (December 2004 Issue) The Brain's Own Marijuana
- Ramström, J. (2003), Adverse Health Consequences of Cannabis Use, A Survey of Scientific Studies Published up to and including the Autumn of 2003, National institute of public health, Sweden, Stockholm.
- Hall, W., Solowij, N., Lemon, J., The Health and Psychological Consequences of Cannabis Use. Canberra: Australian Government Publishing Service; 1994.
- World Health Organisation, PROGRAMME ON SUBSTANCE ABUSE, Cannabis: a health perspective and research agenda;1997.
- Cannabis and mental health factsheet
- Bibliography of scholarly histories on cannabis and hashish. (Updated to include article abstracts.)
- Marijuana and Immunity
- The National Cannabis Prevention and Information Centre (Australia)
- EU Research paper on the potency of Cannabis (2004)(.pdf)
- Driving under the influence of cannabis: a brief review of the literature
- Cannabis Contamination Research Brief
- Cannabinoids and appetite
- NCPIC e-zine December 2007/ January 2008 Commentary on cannabis toxicity research and Moir report
- Cannabis and mental health factsheet
- Cannabis use and reproduction
- Evidence-based answers to cannabis questions
- NCPIC Cannabis and alcohol factsheet