Substance use disorder
Encyclopedia
Substance use disorders include substance abuse
Substance abuse
A substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...

 and substance dependence
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

. In DSM-IV, the conditions are formally diagnosed as one or the other, but it has been proposed that DSM-5
DSM-5
The next edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders , commonly called DSM-5 , is currently in consultation, planning and preparation...

 combine the two into a single condition called "Substance-use disorder".

Terminology and usage

Although the term substance can refer to any physical matter, "substance abuse" has come to refer to the overindulgence in and dependence of a drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...

 or other chemical leading to effects that are detrimental to the individual's physical and mental health, or the welfare
Quality of life
The term quality of life is used to evaluate the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of...

 of others.

The disorder is characterized by a pattern of continued pathological use of a medication, non-medically indicated drug or toxin
Drug abuse
Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts...

, which results in repeated adverse social consequences related to drug use, such as failure to meet work, family, or school obligations, interpersonal conflicts, or legal problems. There are on-going debates as to the exact distinctions between substance abuse and substance dependence
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

, but current practice standard distinguishes between the two by defining substance dependence in terms of physiological and behavioral symptoms of substance use, and substance abuse in terms of the social consequences of substance use.

Substance abuse may lead to addiction or substance dependence. Medically, physiologic dependence requires the development of tolerance
Physiological tolerance
Physiological tolerance or drug tolerance is commonly encountered in pharmacology, when a subject's reaction to a drug is reduced at a later time even though the dose or concentration at the effect site is the same. This means that larger doses are required to achieve the same effect...

 leading to withdrawal
Withdrawal
Withdrawal can refer to any sort of separation, but is most commonly used to describe the group of symptoms that occurs upon the abrupt discontinuation/separation or a decrease in dosage of the intake of medications, recreational drugs, and alcohol...

 symptoms. Both abuse and dependence are distinct from addiction
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

 which involves a compulsion
Compulsive behavior
Compulsive behavior is behavior which a person does compulsively—in other words, not because they want to behave that way, but because they feel they have to do so....

 to continue using the substance despite the negative consequences, and may or may not involve chemical dependency. Dependence almost always implies abuse, but abuse frequently occurs without dependence, particularly when an individual first begins to abuse a substance. Dependence involves physiological processes while substance abuse reflects a complex interaction between the individual, the abused substance and society.

Substance abuse is sometimes used as a synonym for drug abuse
Drug abuse
Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts...

, drug addiction, and chemical dependency, but actually refers to the use of substances in a manner outside sociocultural conventions. All use of controlled drug
Controlled Drug
The United Kingdom Misuse of Drugs Act 1971 aimed to control the possession and supply of numerous listed drugs and drug-like substances as a controlled substance. The act allowed and regulated the use of some Controlled Drugs by various classes of persons The United Kingdom Misuse of Drugs Act...

s and all use of other drugs in a manner not dictated by convention (e.g. according to physician's orders or societal norms) is abuse according to this definition, however there is no universally accepted definition of substance abuse.

The physical harm for twenty drugs was compared in an article in the Lancet (see diagram, above right). Physical harm was assigned a value from 0 to 3 for acute harm, chronic harm and intravenous harm. Shown is the mean physical harm. Not shown, but also evaluated, was the social harm.

Substance use may be better understood as occurring on a spectrum from beneficial to problematic use. This conceptualization moves away from the ill-defined binary antonyms of "use" vs. "abuse" (see diagram, lower right) towards a more nuanced, public health-based understanding of substance use.

Mediators & Moderators

When a predictor variable and an outcome variable have a significant relationship, which is, in turn, influenced by a third variable, the relationship is said to be mediated by the third variable. In this relationship the predictor variable influences the mediating variable in a causal manner. This mediating variable then leads to the outcome, creating the relationship between the predictor and outcome. It is only because of this mediating variable that a relationship between the predictor and outcome exists. Also, quasi-causal inferences may be drawn from mediated relationships. Mediation is best illustrated by the following model:

As demonstrated by the chart below, numerous studies have examined factors which mediate substance abuse or dependence. In these examples, the predictor variables lead to the mediator which in turn leads to the outcome, which is always substance abuse or dependence. For example, research has found that being raised in a single-parent home can lead to increased exposure to stress and that increased exposure to stress, not being raised in a single-parent home, leads to substance abuse or dependence. The following are some, but by no means all, of the possible mediators of substance abuse.
Predictor Variables Mediator Variables Outcome Variable
Single-parent Home Exposure to Stress, Association w/ Deviant Peers Substance Abuse or Dependence
Child Abuse
Child abuse
Child abuse is the physical, sexual, emotional mistreatment, or neglect of a child. In the United States, the Centers for Disease Control and Prevention and the Department of Children And Families define child maltreatment as any act or series of acts of commission or omission by a parent or...

/Neglect
Child neglect
Child neglect is defined as:# "the failure of a person responsible for a child’s care and upbringing to safeguard the child’s emotional and physical health and general well-being"...

PTSD symptoms, Stressful Life Events, Criminal Behavior Substance Abuse or Dependence
Parental Substance Abuse
Witnessing Violence
Physical
Physical abuse
Physical abuse is abuse involving contact intended to cause feelings of intimidation, injury, or other physical suffering or bodily harm.-Forms of physical abuse:*Striking*Punching*Belting*Pushing, pulling*Slapping*Whipping*Striking with an object...

/Sexual Abuse
Sexual abuse
Sexual abuse, also referred to as molestation, is the forcing of undesired sexual behavior by one person upon another. When that force is immediate, of short duration, or infrequent, it is called sexual assault. The offender is referred to as a sexual abuser or molester...


Delinquency Status
Substance Abuse or Dependence


When a variable indicates the conditions under which a specific effect occurs as well as displays how the direction or strength varies within a given relationship, the variable is said to moderate the relationship. Another explanation is that a moderator variable indicates that an effect only occurs under specific conditions. Unlike a relationship containing a mediator variable, the impact of the predictor variable on the outcome is dependent on the value of the moderating variable. Also unlike a relationship involving mediation, no causal inferences can be drawn from a moderated relationship; relationships can only be described as correlated. However, moderated relationships do identify interaction effects between predictor and moderator variables. Moderation is best illustrated by the following model:

As demonstrated by the chart below, numerous studies have examined factors which moderate substance abuse or dependence. In these examples, the moderator variable impacts the level to which the strength of the relationship varies between a given predictor variable and the outcome of substance abuse or dependence. For example, there is a significant relationship between psychobehavioral risk factors, such as tolerance of deviance, rebelliousness, achievement, perceived drug risk, familism, family church attendance and other factors, and substance abuse and dependence. That relationship is moderated by familism which means that the strength of the relationship is increased or decreased based on the level of familism present in a given individual.
Predictor Variables Moderator Variables Outcome Variable
Psychobehavioral Risk Familism
Family Church Attendance
Substance Abuse or Dependence
Victimization Effects Race/Ethnicity
Physical/Sexual Abuse
Substance Abuse or Dependence
Family History of Alcoholism Gender Substance Abuse or Dependence


Mediation and moderation research continues to inform the field’s knowledge and understanding of a pervasive and dangerous threat to public health, substance abuse and dependence. As the relationships between various predictor variables and the factors which influence them are more closely scrutinized, clinicians and researchers are provided with the necessary information to create more sophisticated and relevant methods of prevention and intervention. While these factors are important to the development of SUDs, there are plenty of other factors both known and unknown that influence the development of this disorder. As such, continued research is both necessary and invaluable.

Additional Mediators and Moderators of Substance Abuse

Mediators and Moderators Defined:
Baron and Kenny (1986) define a moderator as, “a qualitative (e.g., sex, race, class) or quantitative (e.g., level of reward) variable that affects the direction and/or strength of the relation between and independent or predictor variable and a dependent or criterion variable” (p. 1174). Moderators may operate as protective factors, decreasing the strength of the relationship between the predictor variable and the outcome. Conversely, moderators may heighten risk levels and strengthen the effects of the predictor on the outcome. In either instance, moderators do not explain why the connection exists, but rather affect the strength and direction of the relationship between the variables.

A mediator, as defined by Baron and Kenny (1986), “represents the generative mechanism through which the focal independent variable is able to influence the dependent variable of interest” (p. 1173). Unlike moderators, mediators can explain the relationship between the predictor variable and outcome. Holmbeck (1997) elaborated on Baron and Kenny’s definition by adding, “the nature of the mediated relationship is such that the independent variable influences the mediator which, in turn, influences the outcome” (p. 600).
Examples of mediators and moderators in empirical research:

Examples of mediators and moderators can be found in several empirical studies. For example, Pilgrim et al.’s hypothesized mediation model posited that school success and time spent with friends mediated the relationship between parental involvement and risk-taking behavior with substance use (2006). More specifically, the relationship between parental involvement and risk-taking behavior is explained via the interaction with third variables, school success and time spent with friends. In this example, increased parental involvement led to increased school success and decreased time with friends, both of which were associated with decreased drug use. Another example of mediation involved risk-taking behaviors. As risk-taking behaviors increased, school success decreased and time with friends increased, both of which were associated with increased drug use.
A second example of a mediating variable is depression. In a study by Lo and Cheng (2007), depression was found to mediate the relationship between childhood maltreatment and subsequent substance abuse in adulthood. In other words, childhood physical abuse is associated with increased depression, which in turn, in associated with increased drug and alcohol use in young adulthood. More specifically, depression helps to explain how childhood abuse is related to subsequent substance abuse in young adulthood.

A third example of a mediating variable is an increase of externalizing symptoms. King and Chassin (2008) conducted research examining the relationship between stressful life events and drug dependence in young adulthood. Their findings identified problematic externalizing behavior on subsequent substance dependency. In other words, stressful life events are associated with externalizing symptoms, such as aggression or hostility, which can lead to peer alienation or acceptance by socially deviant peers, which could lead to increased drug use. The relationship between stressful life events and subsequent drug dependence however exists via the presence of the mediation effects of externalizing behaviors.

An example of a moderating variable is level of cognitive distortion. An individual with high levels of cognitive distortion might react adversely to potentially innocuous events, and may have increased difficulty reacting to them in an adaptive manner (Shoal & Giancola, 2005). In their study, Shoal and Giancola investigated the moderating effects of cognitive distortion on adolescent substance use. Individuals with low levels of cognitive distortion may be more apt to choose more adaptive methods of coping with social problems, thereby potentially reducing the risk of drug use. Individuals with high levels of cognitive distortions, because of their increased misperceptions and misattributions, are at increased risk for social difficulties. Individuals may be more likely to react aggressively or inappropriately, potentially alienating themselves from their peers, thereby putting them at greater risk for delinquent behaviors, including substance use and abuse. In this study, social problems are a significant risk factor for drug use when moderated by high levels of cognitive distortions.

Terminology

In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, physical dependence
Physical dependence
Physical dependence refers to a state resulting from chronic use of a drug that has produced tolerance and where negative physical symptoms of withdrawal result from abrupt discontinuation or dosage reduction...

, abuse
Drug abuse
Substance abuse, also known as drug abuse, refers to a maladaptive pattern of use of a substance that is not considered dependent. The term "drug abuse" does not exclude dependency, but is otherwise used in a similar manner in nonmedical contexts...

 of, and withdrawal
Withdrawal
Withdrawal can refer to any sort of separation, but is most commonly used to describe the group of symptoms that occurs upon the abrupt discontinuation/separation or a decrease in dosage of the intake of medications, recreational drugs, and alcohol...

 from drugs
DRUGS
Destroy Rebuild Until God Shows are an American post-hardcore band formed in 2010. They released their debut self-titled album on February 22, 2011.- Formation :...

 and other substances
Substance abuse
A substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...

 is outlined in the Diagnostic and Statistical Manual of Mental Disorders
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

 (DSM-IV TR). It does not use the word 'addiction' at all. It has instead a section about Substance dependence
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

:
"Substance dependence When an individual persists in use of alcohol or other drugs despite problems related to use of the substance, substance dependence
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

 may be diagnosed. Compulsive and repetitive use may result in tolerance to the effect of the drug and withdrawal symptoms when use is reduced or stopped. This, along with Substance Abuse
Substance abuse
A substance-related disorder is an umbrella term used to describe several different conditions associated with several different substances .A substance related disorder is a condition in which an individual uses or abuses a...

 are considered Substance Use Disorders..."


Terminology has become quite complicated in the field. Pharmacologists continue to speak of addiction from a physiologic standpoint (some call this a physical dependence
Physical dependence
Physical dependence refers to a state resulting from chronic use of a drug that has produced tolerance and where negative physical symptoms of withdrawal result from abrupt discontinuation or dosage reduction...

); psychiatrists refer to the disease state as psychological dependence
Substance dependence
The section about substance dependence in the Diagnostic and Statistical Manual of Mental Disorders does not use the word addiction at all. It explains:...

; most other physicians refer to the disease as addiction. The field of psychiatry is now considering, as they move from DSM-IV to DSM-V, transitioning from "substance dependence" to "addiction" as terminology for the disease state.

Addiction is now narrowly defined as "uncontrolled, compulsive use"; if there is no harm being suffered by, or damage done to, the patient or another party, then clinically it may be considered compulsive
Compulsive behavior
Compulsive behavior is behavior which a person does compulsively—in other words, not because they want to behave that way, but because they feel they have to do so....

, but to the definition of some it is not categorized as 'addiction'. In practice, the two kinds of addiction are not always easy to distinguish. Addictions often have both physical and psychological components.

There is also a lesser known situation called pseudo-addiction. A patient will exhibit drug-seeking behavior reminiscent of psychological addiction, but they tend to have genuine pain or other symptoms that have been under-treated. Unlike true psychological addiction, these behaviors tend to stop when the pain is adequately treated.

Physical and psychological dependency

The medical community now makes a careful theoretical distinction between physical dependence (characterized by symptoms of withdrawal
Withdrawal
Withdrawal can refer to any sort of separation, but is most commonly used to describe the group of symptoms that occurs upon the abrupt discontinuation/separation or a decrease in dosage of the intake of medications, recreational drugs, and alcohol...

) and psychological dependence (or simply addiction).

The DSM definition of addiction can be boiled down to compulsive use of a substance (or engagement in an activity) despite ongoing negative consequences—this is also a summary of what used to be called "psychological dependency." Physical dependence, on the other hand, is simply needing a substance to function. Humans are all physically dependent on oxygen, food and water. A drug can cause physical dependence and not addiction (for example, some blood pressure medications, which can produce fatal withdrawal symptoms if not tapered) and can cause addiction without physical dependence (the withdrawal symptoms associated with cocaine are all psychological, there is no associated vomiting or diarrhea as there is with opiate withdrawal).

Physical dependency

Physical dependence
Physical dependence
Physical dependence refers to a state resulting from chronic use of a drug that has produced tolerance and where negative physical symptoms of withdrawal result from abrupt discontinuation or dosage reduction...

 on a substance is defined by the appearance of characteristic withdrawal
Withdrawal
Withdrawal can refer to any sort of separation, but is most commonly used to describe the group of symptoms that occurs upon the abrupt discontinuation/separation or a decrease in dosage of the intake of medications, recreational drugs, and alcohol...

 symptoms when the substance is suddenly discontinued. Opiates, benzodiazepine
Benzodiazepine
A benzodiazepine is a psychoactive drug whose core chemical structure is the fusion of a benzene ring and a diazepine ring...

s, barbiturate
Barbiturate
Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

s, alcohol
Alcohol
In chemistry, an alcohol is an organic compound in which the hydroxy functional group is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms....

 and nicotine
Nicotine
Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

 induce physical dependence. On the other hand, some categories of substances share this property and are still not considered addictive: cortisone
Cortisone
Cortisone is a steroid hormone. It is one of the main hormones released by the adrenal gland in response to stress. In chemical structure, it is a corticosteroid closely related to corticosterone. It is used to treat a variety of ailments and can be administered intravenously, orally,...

, beta blocker
Beta blocker
Beta blockers or beta-adrenergic blocking agents, beta-adrenergic antagonists, beta-adrenoreceptor antagonists or beta antagonists, are a class of drugs used for various indications. They are particularly for the management of cardiac arrhythmias, cardioprotection after myocardial infarction ,...

s and most antidepressant
Antidepressant
An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;...

s are examples. So, while physical dependency can be a major factor in the psychology of addiction and most often becomes a primary motivator in the continuation of an addiction, the initial primary attribution of an addictive substance is usually its ability to induce pleasure, although with continued use the goal is not so much to induce pleasure as it is to relieve the anxiety caused by the absence of a given addictive substance, causing it to become used compulsively.

Some substances induce physical dependence or physiological tolerance
Physiological tolerance
Physiological tolerance or drug tolerance is commonly encountered in pharmacology, when a subject's reaction to a drug is reduced at a later time even though the dose or concentration at the effect site is the same. This means that larger doses are required to achieve the same effect...

 - but not addiction — for example many laxative
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...

s, which are not psychoactive; nasal decongestant
Decongestant
A decongestant or nasal decongestant is a type of drug that is used to relieve nasal congestion.-Pharmacology:The vast majority of decongestants act via enhancing norepinephrine and epinephrine or adrenergic activity by stimulating the α-adrenergic receptors...

s, which can cause rebound congestion if used for more than a few days in a row; and some antidepressants, most notably venlafaxine
Venlafaxine
Venlafaxine is an antidepressant of the serotonin-norepinephrine reuptake inhibitor class. First introduced by Wyeth in 1993, now marketed by Pfizer, it is licensed for the treatment of major depressive disorder , as a treatment for generalized anxiety disorder, and comorbid indications in...

, paroxetine
Paroxetine
Paroxetine is an SSRI antidepressant. Marketing of the drug began in 1992 by the pharmaceutical company SmithKline Beecham, now GlaxoSmithKline...

 and sertraline
Sertraline
Sertraline hydrochloride is an antidepressant of the selective serotonin reuptake inhibitor class. It was introduced to the market by Pfizer in 1991. Sertraline is primarily used to treat major depression in adult outpatients as well as obsessive–compulsive, panic, and social anxiety disorders in...

, as they have quite short half-lives
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

, so stopping them abruptly causes a more rapid change in the neurotransmitter balance in the brain than many other antidepressants. Many non-addictive prescription drugs should not be suddenly stopped, so a doctor should be consulted before abruptly discontinuing them.

The speed with which a given individual becomes addicted to various substances varies with the substance, the frequency of use, the means of ingestion, the intensity of pleasure or euphoria, and the individual's genetic and psychological susceptibility. Some people may exhibit alcoholic tendencies from the moment of first intoxication, while most people can drink socially without ever becoming addicted. Opioid dependent individuals have different responses to even low doses of opioids than the majority of people, although this may be due to a variety of other factors, as opioid use heavily stimulates pleasure-inducing neurotransmitters in the brain. Nonetheless, because of these variations, in addition to the adoption and twin studies that have been well replicated, much of the medical community is satisfied that addiction is in part genetically moderated. That is, one's genetic makeup may regulate how susceptible one is to a substance and how easily one may become psychologically attached to a pleasurable routine.

Eating disorder
Eating disorder
Eating disorders refer to a group of conditions defined by abnormal eating habits that may involve either insufficient or excessive food intake to the detriment of an individual's physical and mental health. Bulimia nervosa, anorexia nervosa, and binge eating disorder are the most common specific...

s are complicated pathological mental illnesses and thus are not the same as addictions described in this article. Eating disorders, which some argue are not addictions at all, are driven by a multitude of factors, most of which are highly different than the factors behind addictions described in this article. It has been reported, however, that patients with eating disorders can successfully be treated with the same non-pharmacological protocols used in patients with chemical addiction disorders.
Gambling is another potentially addictive behavior with some biological overlap. Conversely gambling urges have emerged with the administration of Mirapex
Pramipexole
Pramipexole is a non-ergoline dopamine agonist indicated for treating early-stage Parkinson's disease and restless legs syndrome...

 (pramipexole), a dopamine agonist
Agonist
An agonist is a chemical that binds to a receptor of a cell and triggers a response by that cell. Agonists often mimic the action of a naturally occurring substance...

.

The obsolete term physical addiction is deprecated, because of its connotations. In modern pain management with opioids physical dependence is nearly universal. While opiates are essential in the treatment of acute pain, the benefit of this class of medication in chronic pain is not well proven. Clearly, there are those who would not function well without opiate treatment; on the other hand, many states are noting significant increases in non-intentional deaths related to opiate use. High-quality, long-term studies are needed to better delineate the risks and benefits of chronic opiate use.

Psychological dependency

In the now outdated conceptualization of the problem, psychological dependency leads to psychological withdrawal symptoms (such as cravings
Craving (withdrawal)
When going through withdrawal, craving is a psychological urge to administer a discontinued medication or recreational drug.-Duration:The duration that cravings last after discontinuation varies substantially between different addictive drugs...

, irritability
Irritability
Irritability 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; It is usually used to refer to anger or frustration....

, insomnia
Insomnia
Insomnia is most often defined by an individual's report of sleeping difficulties. While the term is sometimes used in sleep literature to describe a disorder demonstrated by polysomnographic evidence of disturbed sleep, insomnia is often defined as a positive response to either of two questions:...

, depression
Depression (mood)
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...

, anorexia
Anorexia (symptom)
Anorexia is the decreased sensation of appetite...

, etc). Addiction can in theory be derived from any rewarding behaviour, and is believed to be strongly associated with the dopaminergic system
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

 of the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

's reward system
Reward system
In neuroscience, the reward system is a collection of brain structures which attempts to regulate and control behavior by inducing pleasurable effects...

 (as in the case of cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...

 and amphetamines). Some claim that it is a habitual
Habit (psychology)
Habits are routines of behavior that are repeated regularly and tend to occur subconsciously. Habitual behavior often goes unnoticed in persons exhibiting it, because a person does not need to engage in self-analysis when undertaking routine tasks...

 means to avoid undesired activity, but typically it is only so to a clinical level in individuals who have emotional, social, or psychological dysfunctions
Mental illness
A mental disorder or mental illness is a psychological or behavioral pattern generally associated with subjective distress or disability that occurs in an individual, and which is not a part of normal development or culture. Such a disorder may consist of a combination of affective, behavioural,...

 (psychological addiction is defined as such), replacing normal positive stimuli not otherwise attained.

A person who is physically dependent, but not psychologically dependent can have their dose slowly dropped until they are no longer physically dependent. However, if that person is psychologically dependent, they are still at serious risk for relapse into abuse and subsequent physical dependence.

Psychological dependence does not have to be limited only to substances; even activities and behavioural patterns can be considered addictions, if they become uncontrollable, e.g. problem gambling, Internet addiction
Internet addiction disorder
Internet addiction disorder , or, more broadly, Internet overuse, problematic computer use or pathological computer use, is excessive computer use that interferes with daily life...

, computer addiction
Computer addiction
Computer addiction is a loosely used term for the excessive use of computers to the extent that it interferes with daily life. Excessive use may explain problems in social interaction, mood, personality, work ethic, relationships, thought processes, or sleep deprivation.The Diagnostic and...

, sexual addiction
Sexual addiction
Sexual addiction is a popular model to explain hypersexuality—sexual urges, behaviors, or thoughts that appear extreme in frequency or feel out of one's control...

 / pornography addiction
Pornography addiction
Pornography addiction, or more broadly overuse of pornography, is excessive pornography use that interferes with daily life.There is no diagnosis of pornography addiction in the current Diagnostic and Statistical Manual of Mental Disorders , and as with the broader proposed diagnosis of sexual...

, overeating
Overeating
Overeating generally refers to the long-term consumption of excess food in relation to the energy that an organism expends , leading to weight gainingand often obesity. It may be regarded as an eating disorder....

, self-injury, compulsive buying
Compulsive buying disorder
Compulsive buying disorder is characterized by an obsession with shopping and buying behavior that causes adverse consequences. Most persons with CBD meet the criteria for an axis II disorder....

, or work addiction.

Management

Early editions of the American Psychiatric Association's
American Psychiatric Association
The 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...

 Diagnostic and Statistical Manual of Mental Disorders
Diagnostic and Statistical Manual of Mental Disorders
The Diagnostic and Statistical Manual of Mental Disorders is published by the American Psychiatric Association and provides a common language and standard criteria for the classification of mental disorders...

 (DSM) described addiction as a physical dependency to a substance that resulted in withdrawal symptoms in its absence. Recent editions, including DSM-IV, have moved toward a diagnostic instrument that classifies such conditions as dependency, rather than addiction.

Addiction severity index

Some medical systems, including those of at least 15 states of the United States, refer to an Addiction Severity Index to assess the severity of problems related to substance use. The index assesses problems in six areas: medical, employment/support, alcohol and other drug use, legal, family/social, and psychiatric.

Detoxification

Early treatment of acute withdrawal often includes medical detoxification, which can include doses of anxiolytic
Anxiolytic
An anxiolytic is a drug used for the treatment of anxiety, and its related psychological and physical symptoms...

s or narcotics to reduce symptoms of withdrawal. An experimental drug, ibogaine
Ibogaine
Ibogaine is a naturally occurring psychoactive substance found in a number of plants, principally in a member of the Apocynaceae family known as Iboga . A hallucinogen with both psychedelic and dissociative properties, the substance is banned in some countries; in other countries it is being used...

, is also proposed to treat withdrawal and craving.

Neurofeedback
Neurofeedback
Neurofeedback , also called neurotherapy, neurobiofeedback or EEG biofeedback is a type of biofeedback that uses realtime displays of electroencephalography or functional magnetic resonance imaging to illustrate brain activity, often with a goal of controlling central nervous system activity...

 therapy has shown statistically significant improvements in numerous researches http://www.neurofeedback-scotland.com/alpha.html conducted on alcoholic as well as mixed substance abuse population. In chronic opiate addiction, a surrogate drug such as methadone
Methadone
Methadone is a synthetic opioid, used medically as an analgesic and a maintenance anti-addictive for use in patients with opioid dependency. It was developed in Germany in 1937...

 is sometimes offered as a form of opiate replacement therapy
Opiate replacement therapy
Opioid replacement therapy is the medical procedure of replacing an illegal opioid drug such as heroin with a longer acting but less euphoric opioid, usually methadone or buprenorphine, that is taken under medical supervision. In some countries patients may be treated with slow-release morphine...

. But treatment approaches universal focus on the individual's ultimate choice to pursue an alternate course of action.

Tailoring treatment

Therapists often classify patients with chemical dependencies as either interested or not interested in changing.

Treatments usually involve planning for specific ways to avoid the addictive stimulus, and therapeutic interventions intended to help a client learn healthier ways to find satisfaction. Clinical leaders in recent years have attempted to tailor intervention approaches to specific influences that affect addictive behavior, using therapeutic interviews in an effort to discover factors that led a person to embrace unhealthy, addictive sources of pleasure or relief from pain.
Treatment modality matrix
Behavioral pattern Intervention Goals
Low self-esteem
Self-esteem
Self-esteem is a term in psychology to reflect a person's overall evaluation or appraisal of his or her own worth. Self-esteem encompasses beliefs and emotions such as triumph, despair, pride and shame: some would distinguish how 'the self-concept is what we think about the self; self-esteem, the...

, anxiety, verbal hostility
Relationship therapy, client centered approach Increase self esteem, reduce hostility and anxiety
Defective personal constructs, ignorance of interpersonal means Cognitive restructuring
Cognitive restructuring
Cognitive restructuring, sometimes used synonymously with Debating, is the process of learning to identify irrational or maladaptive thoughts and challenge their veracity using strategies such as logical disputation....

 including directive and group therapies
Insight
Focal anxiety such as fear of crowds Desensitization Change response to same cue
Undesirable behaviors, lacking appropriate behaviors Aversive conditioning, operant conditioning, counter conditioning Eliminate or replace behavior
Lack of information Provide information Have client act on information
Difficult social circumstances Organizational intervention, environmental manipulation, family counseling Remove cause of social difficulty
Poor social performance, rigid interpersonal behavior Sensitivity training, communication training, group therapy Increase interpersonal repertoire, desensitization to group functioning
Grossly bizarre behavior Medical referral Protect from society, prepare for further treatment
Adapted from: Essentials of Clinical Dependency Counseling, Aspen Publishers


From the applied behavior analysis
Applied Behavior Analysis
Applied behavior analysis is a science that involves using modern behavioral learning theory to modify behaviors. Behavior analysts reject the use of hypothetical constructs and focus on the observable relationship of behavior to the environment...

 literature and the behavioral psychology literature, several evidenced-based intervention programs have emerged (1) behavioral marital therapy (2) community reinforcement approach (3) cue exposure therapy and (4) contingency management strategies. In addition, the same author suggests that social skills training adjunctive to inpatient treatment of alcohol dependence is probably efficacious.

Causes

Several explanations (or "models") have been presented to explain addiction. These divide, more or less, into the models which stress biological or genetic causes for addiction, and those which stress social or purely psychological causes. Of course there are also many models which attempt to see addiction as both a physiological and a psycho-social phenomenon.

Psycho-social

  • The free-will model or "life-process model
    Life-process model of addiction
    The life-process model of addiction is the view that addiction is not a disease but rather a habitual response and a source of gratification and security that can be understood only in the context of social relationships and experiences....

    " proposed by Thomas Szasz
    Thomas Szasz
    Thomas Stephen Szasz is a psychiatrist and academic. Since 1990 he has been Professor Emeritus of Psychiatry at the State University of New York Health Science Center in Syracuse, New York. He is a well-known social critic of the moral and scientific foundations of psychiatry, and of the social...

     and later refined by Jeffrey Schaler questions the very concept of "addiction". Free-will model theorists argue that addiction cannot be a disease, because drug-taking is a behavior, and all behaviors are choice
    Choice
    Choice consists of the mental process of judging the merits of multiple options and selecting one of them. While a choice can be made between imagined options , often a choice is made between real options, and followed by the corresponding action...

    s. Szasz views addiction as a metaphor, and that the only reason to make the distinction between habit and addiction "is to persecute somebody." Free-will model theorists believe that individuals are capable of deliberate action in pursuit of chosen goals, and that physiology alone can never determine whether a person will take a drug, or how often they will take it. Although the free-will model of addiction has received much research support, it is opposed by groups like the American Psychiatric Association
    American Psychiatric Association
    The 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...

     and the National Institute of Mental Health
    National Institute of Mental Health
    The National Institute of Mental Health is one of 27 institutes and centers that make up the National Institutes of Health...

    .

  • The pleasure
    Pleasure
    Pleasure describes the broad class of mental states that humans and other animals experience as positive, enjoyable, or worth seeking. It includes more specific mental states such as happiness, entertainment, enjoyment, ecstasy, and euphoria...

     model proposed by professor Nils Bejerot
    Nils Bejerot
    Nils Bejerot was a Swedish psychiatrist and criminologist best known for his work on drug abuse and for coining the phrase, Stockholm syndrome.-Work:...

    . Addiction "is an emotional fixation (sentiment) acquired through learning, which intermittently or continually expresses itself in purposeful, stereotyped behavior with the character and force of a natural drive, aiming at a specific pleasure or the avoidance of a specific discomfort." "The pleasure mechanism may be stimulated in a number of ways and give rise to a strong fixation on repetitive behavior. Stimulation with drugs is only one of many ways, but one of the simplest, strongest,and often also the most destructive" "If the pleasure stimulation becomes so strong that it captivates an individual with the compulsion and force characteristic of natural drives, then there exists...an addiction" The pleasure model is used as one of the reason for zero tolerance
    Zero tolerance
    Zero tolerance imposes automatic punishment for infractions of a stated rule, with the intention of eliminating undesirable conduct. Zero-tolerance policies forbid persons in positions of authority from exercising discretion or changing punishments to fit the circumstances subjectively; they are...

     for use of illicit drugs.

  • The experiential model devised by Stanton Peele
    Stanton Peele
    Stanton Peele, Ph. D., J.D., is a licensed psychologist, attorney, practicing psychotherapist and the author of books and articles on the subject of alcoholism, addiction and addiction treatment.His awards have included:1989...

     argues that addictions occur with regard to experiences generated by various involvements, whether drug-induced or not. This model is in opposition to the disease, genetic, and neurobiological approaches. Among other things, it proposes that addiction is both more temporary or situational than the disease model claims, and is often outgrown through natural processes.

  • The opponent-process model generated by Richard Soloman states that for every psychological event A will be followed by its opposite psychological event B. For example, the pleasure one experiences from heroin is followed by an opponent process of withdrawal, or the terror of jumping out of an airplane is rewarded with intense pleasure when the parachute opens. This model is related to the opponent process color theory. If you look at the color red then quickly look at a gray area you will see green. There are many examples of opponent processes in the nervous system including taste, motor movement, touch, vision, and hearing. Opponent-processes occurring at the sensory level may translate "down-stream" into addictive or habit-forming behavior.

  • The allostatic (stability through change) model generated by George Koob
    George Koob
    George F. Koob, is a Professor and Chair of the Committee on the Neurobiology of Addictive Disorders at The Scripps Research Institute and Adjunct Professor of Psychology, Psychiatry, and Skaggs School of Pharmacy and Pharmaceutical Sciences at the University of California, San Diego.- Biography...

     and Michel LeMoal is a modification of the opponent process theory where continued use of a drug leads to a spiralling of uncontrolled use, negative emotional states and withdrawal and a shift into use to new allostatic set point which is lower than that maintained before use of the drug.

  • The cultural
    Culture
    Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

     model recognizes that the influence of culture is a strong determinant of whether or not individuals fall prey to certain addictions. For example, alcoholism is rare among Saudi Arabia
    Saudi Arabia
    The Kingdom of Saudi Arabia , commonly known in British English as Saudi Arabia and in Arabic as as-Sa‘ūdiyyah , is the largest state in Western Asia by land area, constituting the bulk of the Arabian Peninsula, and the second-largest in the Arab World...

    ns, where obtaining alcohol is difficult and using alcohol is prohibited. In North America, on the other hand, the incidence of gambling
    Gambling
    Gambling is the wagering of money or something of material value on an event with an uncertain outcome with the primary intent of winning additional money and/or material goods...

     addictions soared in the last two decades of the 20th century, mirroring the growth of the gaming industry. Half of all patients diagnosed as alcoholic are born into families where alcohol is used heavily, suggesting that familiar influence, genetic factors, or more likely both, play a role in the development of addiction. What also needs to be noted is that when people don't gain a sense of moderation through their development they can be just as likely, if not more, to abuse substances than people born into alcoholic families.

  • The moral
    Moral
    A moral is a message conveyed or a lesson to be learned from a story or event. The moral may be left to the hearer, reader or viewer to determine for themselves, or may be explicitly encapsulated in a maxim...

     model states that addictions are the result of human weakness, and are defects of character
    Moral character
    Moral character or character is an evaluation of a particular individual's durable moral qualities. The concept of character can imply a variety of attributes including the existence or lack of virtues such as integrity, courage, fortitude, honesty, and loyalty, or of good behaviors or habits...

    . Those who advance this model do not accept that there is any biological basis for addiction. They often have scant sympathy for people with serious addictions, believing either that a person with greater moral strength could have the force of will to break an addiction, or that the addict demonstrated a great moral failure in the first place by starting the addiction. The moral model is widely applied to dependency on illegal substances, perhaps purely for social or political reasons, but is no longer widely considered to have any therapeutic value. Elements of the moral model, especially a focus on individual choices, have found enduring roles in other approaches to the treatment of dependencies.

  • Similarly, the rational addiction
    Rational addiction
    Rational addiction is the hypothesis that addictions can be usefully modeled as specific kinds of rational, forward-looking, optimal consumption plans. The canonical theory is due to Kevin M. Murphy and Nobel Prize Winner Gary S. Becker...

     model hypothesizes that addictions (to heroin, tobacco, television, etc.) can be usefully modeled as specific kinds of rational, forward-looking, optimal consumption plans. In other words, addiction is perceived as a rational response to individual and/or environmental factors.

  • The chemical model : Nearly all drugs, directly or indirectly, target the brain’s reward system by flooding the circuit with dopamine. As a person continues to overstimulating the “reward circuit”, the brain adapts to the overwhelming surges in dopamine by producing less of the hormones or by reducing the number of receptors in the reward circuit. As a result, the chemical’s impact on the reward circuit is lessened, reducing the abuser’s ability to enjoy the things that previously brought pleasure. This decrease compels those addicted to dopamine to increase the drug consumption in order to attempt to bring their "feel-good" hormone level back to normal —an effect known as tolerance. Development of dopamine tolerance can eventually lead to profound changes in neurons and brain circuits, with the potential to severely compromise the long-term health of the brain. Modern antipsychotics are designed to block dopamine function. Unfortunately, this blocking can also cause relapses in depression, and can increase addictive behaviors.

  • Finally, the blended model attempts to consider elements of all other models in developing a therapeutic approach to dependency. It holds that the mechanism of dependency is different for different individuals, and that each case must be considered on its own merits.

Physiological

  • The disease model of addiction
    Disease model of addiction
    The disease model of addiction describes an addiction as a lifelong disease involving biologic and environmental sources of origin. The traditional medical model of disease requires only that an abnormal condition be present that causes discomfort, dysfunction, or distress to the individual...

     holds that addiction is a disease
    Disease
    A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

    , coming about as a result of either the impairment of neurochemical
    Neurochemistry
    Neurochemistry is the specific study of neurochemicals, which include neurotransmitters and other molecules such as neuro-active drugs that influence neuron function. This principle closely examines the manner in which these neurochemicals influence the network of neural operation...

     or behavioral processes, or of some combination of the two. Within this model, addictive disease is treated by specialists in Addiction Medicine
    Addiction Medicine
    Addiction medicine is a medical specialty that deals with the treatment of addiction. The specialty often crosses over into other areas, since various aspects of addiction fall within the fields of public health, psychology, social work, psychiatry, and internal medicine, among others...

    . Within the clinical field, the American Medical Association
    American Medical Association
    The American Medical Association , founded in 1847 and incorporated in 1897, is the largest association of medical doctors and medical students in the United States.-Scope and operations:...

    , National Association of Social Workers, and American Psychological Association
    American Psychological Association
    The American Psychological Association is the largest scientific and professional organization of psychologists in the United States. It is the world's largest association of psychologists with around 154,000 members including scientists, educators, clinicians, consultants and students. The APA...

     all have policies which are predicated on the theory that addictive processes represent a disease state. Most treatment approaches, as well, are based on the idea that dependencies are behavioral dysfunctions, and, therefore, contain, at least to some extent, elements of physical or mental disease. Organizations such as the American Society of Addiction Medicine
    American Society of Addiction Medicine
    The American Society of Addiction Medicine is a physician society with a focus on addiction and its treatment.- History :ASAM has its roots in research and clinical traditions that pre-date its founding in the early 1950s, when Ruth Fox, M.D. began regular meetings with other physicians interested...

     believe the research-based evidence for addiction's status as a disease is overwhelming.

  • The genetic
    Genetics
    Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

     model posits a genetic predisposition to certain behaviors. It is frequently noted that certain addictions "run in the family," and while researchers continue to explore the extent of genetic influence, many researchers argue that there is strong evidence that genetic predisposition is often a factor in dependency.


The development of addiction is thought to involve a simultaneous process of 1) increased focus on and engagement in a particular behavior and 2) the attenuation or "shutting down" of other behaviors. For example, under certain experimental circumstances such as social deprivation
Social deprivation
Social deprivation is the reduction or prevention of culturally normal interaction between an individual and the rest of society. This social deprivation is included in a broad network of correlated factors that contribute to social exclusion; these factors include mental illness, poverty, poor...

 and boredom, animals allowed the unlimited ability to self-administer certain psychoactive drugs will show such a strong preference that they will forgo food, sleep, and sex for continued access. The neuro-anatomical correlate of this is that the brain regions involved in driving goal-directed behavior grow increasingly selective for particular motivating stimuli and rewards, to the point that the brain regions involved in the inhibition of behavior can no longer effectively send "stop" signals. A good analogy is to imagine flooring the gas pedal in a car with very bad brakes. In this case, the limbic system is thought to be the major "driving force" and the orbitofrontal cortex is the substrate of the top-down inhibition.

A specific portion of the limbic circuit known as the mesolimbic
Mesolimbic pathway
The mesolimbic pathway is one of the dopaminergic pathways in the brain. The pathway begins in the ventral tegmental area of the midbrain and connects to the limbic system via the nucleus accumbens, the amygdala, and the hippocampus as well as to the medial prefrontal cortex...

 dopaminergic system is hypothesized to play an important role in translation of motivation to motor behavior- and reward-related learning in particular. It is typically defined as the ventral tegmental area (VTA), the nucleus accumbens, and the bundle of dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...

-containing fibers that are connecting them. This system is commonly implicated in the seeking out and consumption of rewarding stimuli or events, such as sweet-tasting foods or sexual interaction. However, its importance to addiction research goes beyond its role in "natural" motivation: while the specific site or mechanism of action may differ, all known drugs of abuse have the common effect in that they elevate the level of dopamine in the nucleus accumbens. This may happen directly, such as through blockade of the dopamine re-uptake mechanism (see cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...

). It may also happen indirectly, such as through stimulation of the dopamine-containing neurons of the VTA that synapse onto neurons in the accumbens (see opiates). The euphoric effects of drugs of abuse are thought to be a direct result of the acute increase in accumbal dopamine.

The human body has a natural tendency to maintain homeostasis
Homeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...

, and the central nervous system is no exception. Chronic elevation of dopamine will result in a decrease in the number of dopamine receptors available in a process known as downregulation. The decreased number of receptors changes the permeability of the cell membrane located post-synaptically, such that the post-synaptic neuron is less excitable- i.e.: less able to respond to chemical signaling with an electrical impulse, or action potential
Action potential
In physiology, an action potential is a short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and...

. It is hypothesized that this dulling of the responsiveness of the brain's reward pathways contributes to the inability to feel pleasure, known as anhedonia
Anhedonia
In psychology and psychiatry, anhedonia is defined as the inability to experience pleasure from activities usually found enjoyable, e.g. hobbies, exercise, social interaction or sexual activity....

, often observed in addicts. The increased requirement for dopamine to maintain the same electrical activity is the basis of both physiological tolerance
Physiological tolerance
Physiological tolerance or drug tolerance is commonly encountered in pharmacology, when a subject's reaction to a drug is reduced at a later time even though the dose or concentration at the effect site is the same. This means that larger doses are required to achieve the same effect...

 and withdrawal associated with addiction.

Downregulation can be classically conditioned. If a behavior consistently occurs in the same environment or contingently with a particular cue, the brain will adjust to the presence of the conditioned cues by decreasing the number of available receptors in the absence of the behavior. It is thought that many drug overdoses are not the result of a user taking a higher dose than is typical, but rather that the user is administering the same dose in a new environment.

In cases of physical dependency on depressant
Depressant
A depressant, or central depressant, is a drug or endogenous compound that depresses the function or activity of a specific part of the brain...

s of the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 such as opioids, barbiturate
Barbiturate
Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

s, or alcohol, the absence of the substance can lead to symptoms of severe physical discomfort. Withdrawal from alcohol or sedatives such as barbiturates or benzodiazepines (valium-family) can result in seizures and even death. By contrast, withdrawal from opioids, which can be extremely uncomfortable, is rarely if ever life-threatening. In cases of dependence and withdrawal, the body has become so dependent on high concentrations of the particular chemical that it has stopped producing its own natural versions (endogenous ligands) and instead produces opposing chemicals. When the addictive substance is withdrawn, the effects of the opposing chemicals can become overwhelming. For example, chronic use of sedatives (alcohol, barbiturate
Barbiturate
Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

s, or benzodiazepines) results in higher chronic levels of stimulating neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...

s such as glutamate. Very high levels of glutamate kill nerve cells, a phenomenon called excitatory neurotoxicity.

Epidemiology

Note: Citation or some explanation here is needed badly.

Addiction and drug control legislation

Most countries have legislation which brings various drugs and drug-like substances under the control of licensing systems. Typically this legislation covers any or all of the opiates, amphetamines, cannabinoids
Cannabinoids
Cannabinoids are a class of chemical compounds that include the phytocannabinoids , and chemical compounds that mimic the actions of phytocannabinoids or have a similar structure...

, cocaine
Cocaine
Cocaine is a crystalline tropane alkaloid that is obtained from the leaves of the coca plant. The name comes from "coca" in addition to the alkaloid suffix -ine, forming cocaine. It is a stimulant of the central nervous system, an appetite suppressant, and a topical anesthetic...

, barbiturate
Barbiturate
Barbiturates are drugs that act as central nervous system depressants, and can therefore produce a wide spectrum of effects, from mild sedation to total anesthesia. They are also effective as anxiolytics, as hypnotics, and as anticonvulsants...

s, hallucinogens (tryptamines, LSD
LSD
Lysergic acid diethylamide, abbreviated LSD or LSD-25, also known as lysergide and colloquially as acid, is a semisynthetic psychedelic drug of the ergoline family, well known for its psychological effects which can include altered thinking processes, closed and open eye visuals, synaesthesia, an...

, phencyclidine
Phencyclidine
Phencyclidine , commonly initialized as PCP and known colloquially as angel dust, is a recreational dissociative drug...

, and psilocybin
Psilocybin
Psilocybin is a naturally occurring psychedelic prodrug, with mind-altering effects similar to those of LSD and mescaline, after it is converted to psilocin. The effects can include altered thinking processes, perceptual distortions, an altered sense of time, and spiritual experiences, as well as...

) and a variety of more modern synthetic drugs, and unlicensed production, supply or possession may be a criminal offense.

Usually, however, drug classification under such legislation is not related simply to addictiveness. The substances covered often have very different addictive properties. Some are highly prone to cause physical dependency, whilst others rarely cause any form of compulsive need whatsoever.

Also, although the legislation may be justifiable on moral grounds to some, it can make addiction or dependency a much more serious issue for the individual. Reliable supplies of a drug become difficult to secure as illegally produced substances may have contaminants. Withdrawal from the substances or associated contaminants can cause additional health issues and the individual becomes vulnerable to both criminal abuse and legal punishment. Criminal elements that can be involved in the profitable trade of such substances can also cause physical harm to users.

Opposition to common views

Thomas Szasz
Thomas Szasz
Thomas Stephen Szasz is a psychiatrist and academic. Since 1990 he has been Professor Emeritus of Psychiatry at the State University of New York Health Science Center in Syracuse, New York. He is a well-known social critic of the moral and scientific foundations of psychiatry, and of the social...

 denies that addiction is a psychiatric problem. In many of his works, he argues that addiction is a choice, and that a drug addict is one who simply prefers a socially taboo substance rather than, say, a low risk lifestyle. In Our Right to Drugs, Szasz cites the biography of Malcolm X
Malcolm X
Malcolm X , born Malcolm Little and also known as El-Hajj Malik El-Shabazz , was an African American Muslim minister and human rights activist. To his admirers he was a courageous advocate for the rights of African Americans, a man who indicted white America in the harshest terms for its...

 to corroborate his economic views towards addiction: Malcolm claimed that quitting cigarettes was harder than shaking his heroin addiction. Szasz postulates that humans always have a choice, and it is foolish to call someone an 'addict' just because they prefer a drug
Drug
A drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...

 induced euphoria
Happiness
Happiness is a mental state of well-being characterized by positive emotions ranging from contentment to intense joy. A variety of biological, psychological, religious, and philosophical approaches have striven to define happiness and identify its sources....

 to a more popular and socially welcome lifestyle.

Professor John Booth Davies at the University of Strathclyde
University of Strathclyde
The University of Strathclyde , Glasgow, Scotland, is Glasgow's second university by age, founded in 1796, and receiving its Royal Charter in 1964 as the UK's first technological university...

 has argued in his book The Myth of Addiction that 'people take drugs because they want to and because it makes sense for them to do so given the choices available' as opposed to the view that 'they are compelled to by the pharmacology of the drugs they take'. He uses an adaptation of attribution theory (what he calls the theory of functional attributions) to argue that the statement 'I am addicted to drugs' is functional, rather than veridical. Stanton Peele
Stanton Peele
Stanton Peele, Ph. D., J.D., is a licensed psychologist, attorney, practicing psychotherapist and the author of books and articles on the subject of alcoholism, addiction and addiction treatment.His awards have included:1989...

 has put forward similar views.

Experimentally, Bruce K. Alexander used the classic experiment of Rat Park
Rat Park
Rat Park was a study into drug addiction conducted in the late 1970s , by Canadian psychologist Bruce K. Alexander and his colleagues at Simon Fraser University in British Columbia, Canada....

to show that 'addicted' behaviour in rats only occurred when the rats had no other options. When other options and behavioural opportunities were put in place, the rats soon showed far more complex behaviours.
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