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This article is about the sleep disorder. For other uses, see Sleepwalking (disambiguation) and Sleepwalker (disambiguation).
Classification and external resources
John Everett Millais, The Somnambulist, 1871.
ICD-10 F51.3[1]
ICD-9 307.4
MedlinePlus 000808
eMedicine article/1188854
MeSH D013009

Sleepwalking, also known as somnambulism or noctambulism, is a sleep disorder belonging to the parasomnia family.[2] Sleepwalkers arise from the slow wave sleep stage in a state of low consciousness and perform activities that are usually performed during a state of full consciousness. These activities can be as benign as sitting up in bed, walking to the bathroom, and cleaning, or as hazardous as cooking, driving,[3] violent gestures, grabbing at hallucinated objects,[4] or even homicide.[5][6][7]

Although generally sleepwalking cases consist of simple, repeated behaviours, there are occasionally reports of people performing complex behaviours while asleep, although their legitimacy is often disputed.[8] Sleepwalkers often have little or no memory of the incident, as their consciousness has altered into a state in which it is harder to recall memories. Although their eyes are open, their expression is dim and glazed over.[9] Sleepwalking may last as little as 30 seconds or as long as 30 minutes.[4]

Nomenclature, classification, and codification[edit]

According to a study by Dr. Christina A. Gurnett, of the Washington University School of Medicine's Department of Neurology, sleepwalking may be inherited as an autosomal dominant disorder with reduced penetrance. Genome-wide multipoint parametric linkage analysis for sleepwalking revealed a maximum logarithm of the odds score of 3.44 at chromosome 20q12-q13.12 between 55.6 and 61.4 cM.[10]


Sleep stages[edit]

Sleep is categorized into stages of a cycle between REM sleep and NREM sleep. NREM sleep is further divided into four stages: stage 1 (a light sleep period), stage 2 (a consolidated sleep period), and stage 3 and 4 (slow wave sleep periods). This is followed by stage 3, stage 2, stage 1, and a REM period. In normal adults, a cycle will last about 1.5 hours.[11] According to Lavie, Malhotra, and Pillar, "The length and content of sleep cycles change throughout the night as well as with age." Sleepwalking generally occurs during the first third of the night (between 11 p.m. and 1 a.m.)[9] during the slow wave NREM sleep stage. High delta activity within the brain usually accompanies slow wave NREM sleep, and when 20–50% of all activity is delta activity, stage 3 is scored. When delta activity reaches 50% or higher, stage 4 is scored.[11] Usually, if sleepwalking occurs at all, it will only occur once in a night.[4]


Researchers sometimes disagree about the classification of sleepwalking as an automatism. These repetitive actions may include chewing, lip-smacking, pulling at clothing, or wandering around looking confused. Epileptic automatisms are also associated "with the absence attacks of petit mal epilepsy."[12]

Some actions that take place during sleepwalking could be classified as "automatisms". The distinction between "non-insane automatism" and "insane automatism" may be important in the legal context (see Crime below).


Several experts theorize that the development of sleepwalking in childhood is due to a delay in maturation. There are also high-voltage delta waves in somnambulists up to 17 years of age. This presence might suggest an immaturity in the central nervous system, also a possible cause of sleepwalking.[4] Sleepwalking is clustered in families, and the percentage of childhood sleepwalking increases to 45% if one parent was affected, and 60% if both parents were affected. However, there is no recorded preference to male or female individuals.[9] Thus, heritable factors appear to predispose an individual to develop sleepwalking, but expression of the trait may also be influenced by environmental factors.[13] Other precipitating factors to sleepwalking are those factors which increase the slow wave sleep stage.[14] These most commonly include sleep deprivation, fever, and excessive tiredness. The use of some neuroleptics or hypnotics can also cause sleepwalking to occur.[15]

Another factor that causes a person to sleep walk is stress. Stress causes the body to act up in order to play catch up and bring the systems back to normal. When this happens, our sleep is not excluded from the changes being made. Because sleep is when our body recuperates from the day’s activities, if we go to bed stressed, we cannot fall asleep properly and our systems cannot function properly, causing a change, thus leading to occurrences such as sleep walking.[16] With stress, drug and alcohol consumption has also been linked to sleep walking activity. Though alcohol is a sedative, and usually puts a person to sleep, the quality of sleep they undergo is usually not ideal. Alcohol also tends to increase the number of times the sleeper wakes. Not only is the sleep quality an issue, but with alcohol and the risk of getting up and sleep walking, there is the additional problem with intoxication, which is increased clumsiness. With increased clumsiness comes increased danger for the sleep walker to fall into things or fall down stairs, etc. There are treatments for maintaining sleep quality, ideally lessening, or even more ideally, eliminating sleep walking.[17]


Some drugs can be prescribed for sleepwalkers, such as a low dose of benzodiazepines, such as clonazepam, and tricyclic antidepressants.[4] Many experts advise putting away dangerous items and locking doors and windows before sleep to reduce risks of harmful activity while sleepwalking. Good sleep hygiene and avoiding sleep deprivation is also recommended.[9]



According to the National Sleep Foundation in the U.S., sleepwalking is prevalent in 1–15% of the general populace.[19] Sleepwalking is most prevalent in children, and usually disappears by adolescence. Sleepwalking in adults is less common, but when it does occur, the events occur three times more often per year and last for more years than in children. Sleepwalking in old age is rare and usually indicates another disorder. Old age disorders may include delirium, drug toxicity or a seizure disorder.[4]


Sleepwalking events are common in childhood and decrease with age. According to Lavie, Malhotra and Pillar, the peak age is 4–8 years, when prevalence is 20% frequency of events.[9] Another report states that the peak age is eleven or twelve, with an estimated 25% of children having experienced at least one episode.[20] It is also known that "between 25–33% of somnambulists have nocturnal enuresis" (bed-wetting). Like sleepwalking, enuresis is more common in children and fades away as the child ages. Some children who sleepwalk are also affected by night terrors. However, night terrors are much more common in adult sleepwalkers, up to 50% more common.[4] Some parents worry about the psychological implications of sleepwalking on their child, but Larissa Hirsch, MD, editor of the website KidsHealth, says, "Sleepwalking is not usually a sign that something is emotionally or psychologically wrong with a child. And it doesn't cause any emotional harm."[18]



The persistence or onset of sleepwalking in adulthood is less common than in children. A 2012 study conducted by the Stanford University School of Medicine showed that the prevalence of sleepwalking adults in the United States was higher than once thought, with 3.7% of participants reporting two or more episodes per month.[22] It is a misconception that adult sleepwalking always indicates a psychological disorder. Sleepwalking can, however, be a symptom of people with psychological disorders. In one study, adult test subjects were given the Minnesota Multiphasic Personality Inventory, a psychiatric test. According to the study, patients showed "outwardly directed behavior patterns...suggest[ing] that these adults had difficulty handling aggression. They did not support an interpretation of sleepwalking as 'hysterical dissociation'."[4]

The Australian inventor Myra Juliet Farrell claimed to write the solutions to problems in her sleep.[23] In 2004, sleep medicine experts in Australia claimed to have successfully treated a woman who claimed to have sex with strangers in her sleep.[8] In December 2008, reports were published of a woman who sent semi-coherent emails while sleepwalking, including one inviting a friend around for dinner and drinks.[24]

Psychological disorders and drug use[edit]

In some cases, sleepwalking in adults may be a symptom of a psychological disorder or of drug use. One study, A.H.Crisp and colleagues, of St. George's Hospital Medical School in London, suggests higher levels of dissociation in adult sleepwalkers, since test subjects scored unusually high on the hysteria portion of the "Crown-Crisp Experiential Index".[25] J.E.Orme, of the Psychology Department at Middlewood Hospital, Sheffield has suggested that "A higher incidence [of sleepwalking events] has been reported in patients with schizophrenia, hysteria and anxiety neuroses.".[26] Also, patients with migraine headaches or Tourette Syndrome are 4–6 times more likely to sleepwalk. Some medications that may increase sleepwalking include: chlorpromazine (Thorazine), perphenazine (Trilafon), lithium, triazolam (Halcion), amitriptyline (Elavil, Endep), zolpidem (Ambien) and beta blockers.[4]


Sleepwalking has attracted a sense of mystery, but it had not been seriously investigated and diagnosed until the last century. The 19th-century German chemist and parapsychologist Baron Karl Ludwig von Reichenbach made extensive studies of sleepwalkers and used his discoveries to formulate his theory of the Odic force.




Because sleepwalking can result in violent behavior, legal courts sometimes deal with cases involving sleepwalkers. These cases include homicide, assault, and sexual harassment. The level of responsibility and severity of punishment has been highly debated because sleepwalkers are almost always oblivious to their activity during an episode. According to Culebras, a Professor of Neurology at the State University of New York College of Medicine, "It is conceivable that the sleepwalker has the potential to drift into a confusional arousal, a state in which violence and assault are likely when prolonged and if given the adequate circumstances. The differential diagnosis may also include other conditions in which violence related to sleep is a risk, such as REM Sleep Behavior Disorder (RSBD), fugue states, and episodic wandering."[15] In the 1963 case Bratty v Attorney-General for Northern Ireland, Lord Morris stated, "Each set of facts must require a careful examination of its own circumstances, but if by way of taking an illustration it were considered possible for a person to walk in his sleep and to commit a violent crime while genuinely unconscious, then such a person would not be criminally liable for that act."[31]

In the case of the law, an individual can be accused of non-insane automatism or insane automatism. The first is used as a defense for temporary insanity or involuntary conduct, resulting in acquittal. The latter results in a "special verdict of not guilty by reason of insanity."[32] This verdict of insanity can result in a court order to attend a mental institution.[33]

Other examples of legal cases involving sleepwalking in the defence include:

  • 1999, Arizona v. Falater: Falater, of Phoenix, Arizona, was accused of killing his wife. The court concluded that the murder was too complex to be committed while sleepwalking. Falater was charged with first-degree murder, and given life sentence with no parole.[34]
  • 2008, Brian Thomas, was accused of killing his wife while he dreamt she was an intruder, whilst on holiday in West Wales.[37] Thomas was found not guilty.[38]

Other forms[edit]

One sub category of this sleep-walking occurrence is Sleep Eating Disorder. Similar to sleep walking, the person with the disorder consumes food without being consciously aware they are actually doing this. These sleep eating disorders are more often than not induced by stress related reasons. Another major cause of this phenomenon is sleep medication, such as Ambien for example (Mayo Clinic). There are a few others, but Ambien is a more widely used sleep aid.[39] Because many sleep eaters prepare the food they consume, there are risks involving burns and such with ovens and other appliances. As expected, weight gain is also a common outcome of this disorder, because a food that is frequently found contains high carbohydrates. As with sleep walking, there are ways that sleep eating disorders can be maintained. There are some medications that calm the sleeper so they can get longer and better-quality rest, but more often than not activities such as yoga can be introduced to reduce the stress and anxiety causing the action.[40]


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Further reading[edit]

  • Nicole Edelman, Luis Montiel, and Jean-Pierre Peter: Histoire sommaire de la maladie et du somnambulisme de Lady Lincoln. Paris: Tallandier, 2009.

External links[edit]