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Sleep paralysis
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Sleep paralysis is a condition that may occur in normal subjects or be associated with narcolepsy, cataplexy, and hypnagogic hallucinations. The pathophysiology of this condition is closely related to the normal hypotonia that occur during REM sleep. When considered to be a disease, isolated sleep paralysis is classified as MeSH D020188.
Physiologically, it is closely related to the paralysis that occurs as a natural part of REM (rapid eye movement) sleep, which is known as REM atonia.
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Sleep paralysis is a condition that may occur in normal subjects or be associated with narcolepsy, cataplexy, and hypnagogic hallucinations. The pathophysiology of this condition is closely related to the normal hypotonia that occur during REM sleep. When considered to be a disease, isolated sleep paralysis is classified as MeSH D020188.
Physiologically, it is closely related to the paralysis that occurs as a natural part of REM (rapid eye movement) sleep, which is known as REM atonia. Sleep paralysis occurs when the brain awakes from a REM state, but the body paralysis persists. This leaves the person fully conscious, but unable to move. In addition, the state may be accompanied by terrifying hallucinations (hypnopompic or hypnagogic) and an acute sense of danger. Sleep paralysis is particularly frightening to the individual due to the vividness of such hallucinations. The hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as a dream, since completely fanciful, or dream-like, objects may appear in the room alongside one's normal vision. Some scientists have proposed this condition as an explanation for alien abductions and ghostly encounters. A study by Susan Blackmore and Marcus Cox of the University of the West of England supports the suggestion that alien abductions are related to sleep paralysis rather than to temporal lobe lability.
The paralysis can last from several seconds to several minutes "after which the individual may experience panic symptoms and the realization that the distorted perceptions were false". When there is an absence of narcolepsy, sleep paralysis is referred to as isolated sleep paralysis (ISP). "ISP appears to be far more common and recurrent among African Americans than among White Americans or Nigerian Blacks", and is often referred to within African American communities as "the witch riding your back"
Symptoms
Symptoms of sleep paralysis can be either one of the following or a combination:
- Paralysis: this occurs after waking up or shortly before falling asleep. The person cannot move any body part, and only has minimal control over blinking, breathing, and very rarely, movement of the jaw. This paralysis is the same paralysis that occurs when dreaming. The brain paralyzes the muscles to prevent possible injury during dreams, as some body parts may move during dreaming. If the person wakes up suddenly, the brain may still think that it is dreaming, and sustains the paralysis.
- Hallucinations: Images or speaking that appear during the paralysis. The person may think that someone is standing beside them or they may hear strange sounds. These may be dreamlike, possibly causing the person to think that they are still dreaming. Often it is reported as feeling a weight on one's chest, as if being underneath a person or heavy object.
These symptoms can last from mere seconds to several minutes (although they can feel like much longer) and can be frightening to the person. There may be some body movement, but it is very unlikely and hard for a person to accomplish.
Possible causes
Sleep paralysis occurs during REM sleep, thus preventing the body from manifesting movements made in the subject's dreams. Very little is known about the physiology of sleep paralysis. However, some have suggested that it may be linked to post-synaptic inhibition of motor neurons in the pons region of the brain. In particular, low levels of melatonin may stop the depolarization current in the nerves, which prevents the stimulation of the muscles, to prevent the body from enacting the dream activity (e.g. preventing a sleeper from flailing his legs when dreaming about running).
Several studies have concluded that many or most people will experience sleep paralysis at least once or twice in their lives.
A study conducted by Sedaghat F. et al. has investigated the prevalence of sleep paralysis among Iranian medical students. 24.1% of students reported experiencing sleep paralsis at least once in their lifetime. The same result was reported among Japanese, Nigerian, Kuwaiti, Sudanese and American.
Many people who commonly enter sleep paralysis also suffer from narcolepsy. In African Americans, panic disorder occurs with sleep paralysis more frequently than in Caucasians.
Some reports read that various factors increase the likelihood of both paralysis and hallucinations. These include:
- Sleeping in a face upwards or supine position
- Irregular sleeping schedules; naps, sleeping in, sleep deprivation
- Increased stress
- Sudden environmental/lifestyle changes
- A lucid dream that immediately precedes the episode.
Treatment
Treatment starts with patient education about sleep stages and about the muscle atonia that is typically associated with REM sleep. For most healthy individuals, avoiding chronic sleep deprivation is enough to relieve symptoms. It is recommended that patients be evaluated for narcolepsy if symptoms persist.
Related phenomena
Many perceptions associated with sleep paralysis (visceral buzzing, loud sounds, adrenal mental state, presences, and the paralysis itself) also constitute a common phase in the early progression of episodes referred to as out of body experiences. Mental focus varies between the two conditions; paralysis sufferers tend to fixate on reestablishing operation of the body, whereas subjects of out-of-body episodes are more occupied by perceived non-equivalence with the body.
Folklore
Complete references to many cultures are given in the References section
- In African culture, isolated sleep paralysis is commonly referred to as "the witch riding your back".
- In the Cambodian, Laotian and Thai culture, sleep paralysis is referred to as "pee umm" and "khmout sukkhot". It describes an event where the person is sleeping and dreams that ghostly figure(s) are either holding him/her down or the ghosts can just be near. The person usually thinks that they are awake but is unable to move or make any noises. This is not to be confused with "pee khao" and "khmout jool" which refers to a ghost possession.
- In Hmong culture, sleep paralysis describes an experience called "dab tsog" or "crushing demon" from the compound phrase "dab" (demon) and "tsog" (crush). Often the sufferer claims to be able to see a tiny figure, no larger than a child, sitting on his or her chest. What is alarming is that a vast number of American Hmong, mainly males, have died in their sleep prompting the Centers for Disease Control to create the term "Sudden Unexpected Nocturnal Death Syndrome" (see Sudden unexplained death syndrome) or "SUNDS" for short; this is now theorized to be a form of Brugada syndrome.
- In Vietnamese culture, sleep paralysis is referred to as "ma de", meaning "held down by a ghost" or "bong de", meaning "held down by a shadow". Many people in this culture believe that a ghost has entered one's body, causing the paralyzed state.
- In Chinese culture, sleep paralysis is widely known as "???/???" (pinyin: gui ya shen) or "???/???" (pinyin: gui ya chuáng), which literally translate into "ghost pressing on body" or "ghost pressing on bed." A more modern term is "??/??" (pinyin: mčng yan); notice that the character "?/?" (pinyin: yan) is composed of "?/?" (pinyin: yŕn), "to detest", and "?" (pinyin: gui), "ghost, demon".
- In Japanese culture, sleep paralysis is referred to as kanashibari (, literally "bound or fastened in metal," from kane "metal" and shibaru" to bind, to tie, to fasten"). This term is occasionally used by English speaking authors to refer to the phenomenon both in academic papers and in pop psych literature.
- In Hungarian folk culture sleep paralysis is called "lidércnyomás" ("lidérc pressing") and can be attributed to a number of supernatural entities like "lidérc" (wraith), "boszorkány" (witch), "tündér" (fairy) or "ördögszereto" (demon lover). The word "boszorkány" itself stems from the Turkish root "bas-", meaning "to press".
- In Iceland folk culture sleep paralysis is generally called having a "Mara". Mara is an old Icelandic word for a mare but has taken on the meaning for a sort of a devil that sits on ones chest at night, trying to suffocate the victim.
- In Malta, folk culture attributes a sleep paralysis incident to an attack by the "Haddiela" who is the wife of the "Hares", the entity in Maltese folk culture which haunts the individual in similar ways as to those of a poltergeist. As believed in folk culture, to rid oneself of the Haddiela, one must place a piece of silverware or a knife under the pillow prior to sleep.
- Kurdish people call this phenomenon a "mottaka", they believe that some one, in a form of a ghost or perhaps an evil spirit, turns up on top the of the person in the middle of the night and suffocates him/her. Apparently this happens usually when some one has done something bad.
- In New Guinea, people refer to this phenomenon as "Suk Ninmyo", believed to originate from sacred trees that use human essence to sustain its life. The trees are said to feed on human essence during night as to not disturb the human's daily life, but sometimes people wake unnaturally during the feeding, resulting in the paralysis.
- In Turkish culture, sleep paralysis is often referred to as "karabasan" ("The dark presser/assailer"). It is believed to be a creature which attacks people in their sleep, pressing on their chest and stealing their breath.
- In Mexico, it's believed that sleep paralysis is in fact the spirit of a dead person getting on the person and impeding movement, calling this "se me subió el muerto" (the dead person got on me).
- In many parts of the Southern United States, the phenomenon is known as a "hag", and the event is said to often be a sign of an approaching tragedy or accident.
- Ogun Oru is a traditional explanation for nocturnal disturbances among the Yoruba of Southwest Nigeria; ogun oru (nocturnal warfare) involves an acute night-time disturbance that is culturally attributed to demonic infiltration of the body and psyche during dreaming. Ogun oru is characterized by its occurrence, a female preponderance, the perception of an underlying feud between the sufferer's earthly spouse and a 'spiritual' spouse, and the event of bewitchment through eating while dreaming. The condition is believed to be treatable through Christian prayers or elaborate traditional rituals designed to exorcise the imbibed demonic elements.
- In Greece and Cyprus, it is believed that sleep paralysis occurs when a ghost-like creature or Demon named Mora, Vrahnas or Varypnas (Greek: ???a, ??a????, ?a??p???) tries to steal the victim's speech or sits on the victim's chest causing asphyxiation.
- In Zimbabwean Shona culture the word Madzikirira is used to refer something really pressing one down. This mostly refers to the spiritual world in which some spirit—especially an evil one—tries to use its victim for some evil purpose. The people believe that witches can only be people of close relations to be effective, and hence a witches often try to use one's spirit to bewitch one's relatives.
- In Ethiopian culture the word Dukak is used. Dukak is believed to be some form of evil spirit that possesses people during their sleep. This experience is also believed to be related to use of Khat. Most Khat users experience sleep paralysis when quitting after a long time of use.
- In Ireland it is also known as "the hag". The expression originates from reports of an old woman that was believed to be seen near the sufferer during paralysis.
- Several studies have shown that African-Americans may be predisposed to isolated sleep paralysis also known as "the witch is riding you" or "the haint is riding you". In addition, other studies have shown that African-Americans who have frequent episodes of isolated sleep paralysis, i.e., reporting having one or more sleep paralysis episodes per month coined as "sleep paralysis disorder," were predisposed to having panic attacks. This finding has been replicated by other independent researchers
- In Pakistani culture, it is an encounter with evil jinns and demons. It is also assumed that it is due to the black magic performed by enemies and jealous persons. Curses could also result in ghoul haunting a person. Some homes and locations are also haunted by these satanic beings.
- In Korean Culture, sleep paralysis is known as ???? ("ga-ui nool-lim"), which means "pressed by a nightmare".
- In Tamil and Sri Lankan Culture, this particular phenomenon is referred to as 'Amuku Be" or 'Amuku Pei' meaning "the ghost that forces one down".
- In Malay of Malay Peninsula, sleep paralysis is known as 'kena tindih', which means "being pressed". Incidents are commonly considered to be the work of a malign agency; occurring in what are explained as blind spots in the field of vision, they are reported as demonic figures.
- In Newfoundland and Labrador, it is known as the 'Old Hag'. In island folklore, the Hag can be summoned to attack a third party, like a curse. In his 1982 book, The Terror that Comes in the Night, David J. Hufford writes that in local culture the way to call the Hag is to recite the Lord's Prayer backwards. It is also common for believers to claim that those who are not wakened from this paralysis will die.
External links
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- from Stanford University
- from University of Waterloo
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