Sleepwalking, also known as somnambulism, is a sleep disorder belonging to the parasomnia family. Sleepwalkers arise from the slow wave sleep stage in a state of low consciousness and perform activities that are usually performed during the day. These activities can be as benign as sitting up in bed, walking to the bathroom, and cleaning, or as hazardous as cooking, driving, extremely violent gestures, or even homicide. Other activities such as eating, bathing, urinating, talking, dressing/undressing, texting, emailing, exercising, walking a dog, painting, whistling, dancing, moaning, gesturing, grabbing at apparently hallucinated objects, committing murder, and/or engaging in sexual intercourse are some of the activities that have been reported or claimed to have occurred during sleepwalking. 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. Sleepwalkers often have little or no memory of the incident, as they are not truly conscious. Although their eyes are open, their expression is dim and glazed over. Sleepwalking may last as little as 30 seconds or as long as 30 minutes.
Sleepwalking has attracted a sense of mystery, but it has not been seriously investigated and diagnosed until the last century. Sleepwalking was initially thought to be a dreamer acting out a dream. For example, in one study published by the Society for Science & the Public in 1954, this was the conclusion: “Repression of hostile feelings against the father caused the patients to react by acting out in a dream world with sleepwalking, the distorted fantasies they had about all authoritarian figures, such as fathers, officers and stern superiors.” This same group published an article twelve years later with a new conclusion: “Sleepwalking, contrary to most belief, apparently has little to do with dreaming. In fact, it occurs when the sleeper is enjoying his most oblivious, deepest sleep—a stage in which dreams are not usually reported.” More recent research has discovered that sleepwalking is actually a disorder of NREM (non-rapid eye movement) arousal. Acting out a dream is the basis for a REM (rapid eye movement) sleep disorder called REM Behavior Disorder (or REM Sleep Behavior Disorder, RSBD). More accurate data about sleep is due to the invention of technologies such as the electroencephalogram (EEG) by Hans Berger in 1924 and BEAM by Frank Duffy in the early 1980s.
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. 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.) 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. Usually, if sleepwalking occurs at all, it will only occur once in a night.
Researchers sometimes disagree about the classification of sleepwalking as an automatism. According to the popular source of MedicineNet, an automatism is “an unconscious movement that may resemble simple repetitive tics or may be a complex sequence of natural-looking movements.” The individual often won't remember what they were doing or how they were doing it. 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.” 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.” This verdict of insanity can result in a court order to attend a mental institution. Some actions that take place during sleepwalking could be classified as automatisms.
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. 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. Thus, heritable factors appear to predispose an individual to develop sleepwalking, but expression of the trait may be also influenced by environmental factors. Other precipitating factors to sleepwalking are those factors which increase the slow wave sleep stage. These most commonly include sleep deprivation, fever, and excessive tiredness. The use of some neuroleptics or hypnotics can also cause sleepwalking to occur.
According to the National Sleep Foundation, sleepwalking is prevalent in 1–15% of the general populace. 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.
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. 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. 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.”
In the study "sleepwalking and sleep terrors in prepubera children" they found that if a child had another sleepdisorder such as restless leg syndrom (RLS) or sleep-disorder breathing (SDB) that they had a greater chance of sleepwalking. The study found children with chronic parasomnias may often also present SDB or, to a lesser extent, RLS. Furthermore, the disappearance of the parasomnias after the treatment of the SDB or RLS periodic limb movement syndrome suggests that the latter may trigger the former. The high frequency of SDB in family members of children with parasomnia provided additional evidence that SDB may manifest as parasomnias in children. Children with parasomnias are not systematically monitored during sleep, although past studies have suggested that patients with sleep terrors or sleepwalking have an elevated level of brief EEG arousals. When children receive polysomnographies, discrete patterns (eg, nasal flow limitation, abnormal respiratory effort, bursts of high or slow EEG frequencies) should be sought; apneas are rarely found in children. Children’s respiration during sleep should be monitored with nasal cannula/pressure transducer system and/or esophageal manometry, which are more sensitive than the thermistors or thermocouples currently used in many laboratories. The clear, prompt improvement of severe parasomnia in children who are treated for SDB, as defined here, provides important evidence that subtle SDB can have substantial health-related significance. Also noteworthy is the report of familial presence of parasomnia. Studies of twin cohorts and families with sleep terror and sleepwalking suggest genetic involvement of parasomnias. RLS and SDB have been shown to have familial recurrence. RLS has been shown to have genetic involvement.
The persistence or onset of sleepwalking in adulthood is far less common than in children. 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'."
In some cases, sleepwalking in adults may be a symptom of a psychological disorder or of drug use. One study done by A.H. Crisp et al. of St. George's Hospital Medical School in London supports the possibility of dissociation in adult sleepwalkers because the test subjects scored unusually high on the hysteria portion of the Crown-Crisp experiential index. According to J.E. Orme, an expert in psychology, “A higher incidence [of sleepwalking events] has been reported in patients with schizophrenia, hysteria and anxiety neuroses.” Also, patients with migraine headaches or Tourette Syndrome are 4–6 times more likely to sleepwalk. Some medications that may precipitate sleepwalking include: Chlorpromazine (Thorazine), perphenazine (Trilafon), lithium, benzodiazepine (Triazolam), amitriptylin (Elavel, Endep), Zolpidem (Ambien) and beta blockers.
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 should 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." In the 1963 case Bratty v. Attorney-General for Northern Ireland, Lord Morris of Borth-y-Gest 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."
Examples of sleepwalking cases include:
There are some drugs that can be prescribed for sleepwalkers such as a low dose benzodiazepine, tricyclic antidepressants, and clonazepam. However, for most sleepwalkers, many experts advise putting away dangerous items and locking doors and windows before sleep to reduce risks of harmful activity. Good sleep hygiene and avoiding sleep deprivation is also recommended.
There are conflicting viewpoints on whether it is harmful to wake a sleepwalker. Some experts say that sleepwalkers should be gently guided back to bed without waking them. Others counter that idea and state that waking a sleepwalker may result in their disorientation, but it is not harmful.
Sleepwalking has been found as a theme in many dramatic works. It is a major plot element in the classic silent German Expressionist film Das Cabinet des Dr. Caligari (English title: The Cabinet of Dr. Caligari). In Shakespeare's Macbeth, Lady Macbeth sleepwalks because of her overwhelming guilt and insanity. Sleepwalking is also central for Charles Brockden Brown's 1799 novel Edgar Huntly, Or, Memoirs of a Sleepwalker and in Heinrich Von Kleist's play The Prince of Homburg.
In the film version of Harry Potter and the Half Blood Prince, Luna Lovegood claims that she sleepwalks at night and, as a result, wears her shoes to bed. Also, in the Harry Potter and the Prisoner of Azkaban film Harry Potter uses this as an excuse as to why he was out of bed after hours, when he was really looking for Peter Pettigrew on the Marauder's Map. A sleepwalking murder is the main subject of the 2010 movie In My Sleep.
Italian composer Vincenzo Bellini's opera La Sonnambula is named after its heroine, a sleepwalker. In Dario Argento's Phenomena (1985), the protagonist, Jennifer Corvino (Jennifer Connelly), witnesses a murder while sleepwalking. In the film adaptation of Silent Hill, the protagonist's daughter suffers from sleepwalking. In the House episode "Role Model", a woman has sexsomnia (sexual intercourse with her ex-husband while sleepwalking) and becomes pregnant. In the movie Step Brothers, the main characters, Brennan and Dale, both sleepwalk. In the 1947 Disney animated short "Sleepy Time Donald", Donald Duck is a prolonged sleepwalker, and Daisy Duck steers him away from many hazards.
Dr. John William Polidori, a friend of Lord Byron's, earned his medical degree from the University of Edinburgh in 1815 with a treatise on sleepwalking. He was present at the famous gathering at the Villa Diodati on 16 June 1816 when Byron issued a challenge to him, Percy Bysshe Shelley, Mary Godwin and Claire Clairmont to write a ghost story. Polidori wrote "The Vampyre", the first vampire story in English.