Sleepwalking, also known as somnambulism or noctambulism, is a phenomenon of combined sleep and wakefulness. It is classified as a sleep disorder belonging to the parasomnia family. It occurs during slow wave sleep stage, in a state of low consciousness, with performance of activities that are usually performed during a state of full consciousness. These activities can be as benign as sitting up in bed, walking to a bathroom, and cleaning, or as hazardous as cooking, driving, violent gestures, grabbing at hallucinated objects, or even homicide.
Although sleepwalking cases generally consist of simple, repeated behaviours, there are occasionally reports of people performing complex behaviours while asleep, although their legitimacy is often disputed. 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. This may last from 30 seconds to 30 minutes.
Sleepwalking occurs during slow-wave sleep (N3) of non-rapid eye movement sleep (NREM sleep) cycles. It typically occurs within the first third of the night when slow-wave sleep is most prominent. Usually, it will occur once in a night, if at all.
Signs and symptoms
- No warning: Typically, there is no physiological forewarning that indicates a sleepwalking episode is about to occur. There is no twitching, no increase in heart rate or breathing (directly preceding the episode), and no significant variations in brain waves; there is just quiet, slow-wave sleep until abrupt central nervous system (CNS) arousal prompts the heart rate to accelerate and the sleepwalking begins.
- Glassy-eyed stare/blank expression: During a sleepwalking episode, pupils are typically dilated.
- Disorientation consequent to awakening: The sleepwalker could be confused and perplexed, and might not know why/how they got out of bed; however, the disorientation will go away within minutes.
- Meaningless talk: It is very common that people talk while sleepwalking, but it is typically gibberish.
- Amnesia linked to the event: When children sleepwalk, they usually do not remember anything that happened during their sleepwalking episode. Sleepwalking in adults, however, can vary greatly; they could remember nothing, have a cloudy memory of it, or they might be able to recall the events fairly well.
In the study “sleepwalking and sleep terrors in prepubera children”, it was found that, if a child had another sleep disorder such as restless leg syndrome (RLS) or sleep-disorder breathing (SDB), there was a greater chance of sleepwalking. The study found that 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 (e.g., 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.
In some cases, sleepwalking in adults may be a symptom of a psychological disorder. One study suggests higher levels of dissociation in adult sleepwalkers, since test subjects scored unusually high on the hysteria portion of the “Crown-Crisp Experiential Index”. Another suggested that “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.
The cause of sleepwalking is not known. A number of, as yet unproven, hypotheses are suggested for why it might occur. These include a delay in the maturity of the central nervous system, increased slow wave sleep, sleep deprivation, fever, and excessive tiredness.
There may be a genetic component to sleepwalking. One study found that sleepwalking occurred in 45% of children who have one parent who sleepwalked, and in 60% of children if both parents sleepwalked. Thus, heritable factors may predispose an individual to sleepwalking, but expression of the behavior may also be influenced by environmental factors. Genetic studies using common fruit flies as experimental models reveal a link between night sleep and brain development mediated by evolutionary conserved transcription factors such as AP-2 
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 3.14 at chromosome 20q12-q13.12 between 55.6 and 61.4 cM.
Medications, primarily in four classes—benzodiazepine receptor agonists and other GABA modulators, antidepressants and other serotonergic agents, antipsychotics, and β-blockers— have been associated with sleepwalking. The best evidence of medications causing sleepwalking is for Zolpidem and sodium oxybate—all other reports are based on associations noted in case reports.
A number of conditions, such as Parkinson’s Disease, are thought to trigger sleepwalking in people without a previous history of sleepwalking.
Three common diagnostic systems that are generally used for sleepwalking disorders are International Classification of Diagnoses, the International Classification of Sleep Disorders 3, and the Diagnostic and Statistical Manual. Polysomnography is the only accurate measure of sleepwalking. Other measures commonly used include self-report, parent, partner or house-mate report.
Sleepwalking should not be confused with alcohol- or drug-induced blackouts, which can result in amnesia for events similar to sleepwalking. During an alcohol-induced blackout (drug-related amnesia), a person is able to actively engage and respond to their environment (e.g. having conversations or driving a vehicle), however the brain does not create memories for the events. Alcohol-induced blackouts can occur with blood alcohol levels higher than 0.06g/dl. A systematic review of the literature found that approximately 50% of drinkers have experienced memory loss during a drinking episode and have had associated negative consequences similar to sleepwalkers, including injury and death.
There are two subcategories of sleepwalking: sleepwalking with sleep-related eating, and sleepwalking with sleep-related sexual behavior (sexsomnia).
Sleep eating involves consuming food while asleep. These sleep eating disorders are more often than not induced for stress related reasons. Another major cause of this sleep eating subtype of sleepwalking is sleep medication, such as Ambien for example (Mayo Clinic). There are a few others, but Ambien is a more widely used sleep aid. 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 consumed contains high carbohydrates. As with sleepwalking, 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 activities such as yoga can also be introduced to reduce the stress and anxiety causing the action.
There have been no clinical trials to show that any psychological or pharmacological intervention is effective in preventing sleepwalking episodes. Despite this, a wide range of treatments have been used with sleepwalkers. Psychological interventions have included psychoanalysis, hypnosis, scheduled or anticipatory waking, assertion training, relaxation training, managing aggressive feelings, sleep hygiene, classical conditioning (including electric shock), and play therapy. Pharmacological treatments have included an anticholinergic (biperiden), antiepileptics (carbamazepine, valproate), an antipsychotic (quetiapine), benzodiazepines (clonazepam, diazepam, flurazepam, imipramine, and triazolam), melatonin, a selective serotonin reuptake inhibitor (paroxetine), a barbiturate (sodium amytal) and herbs.
There is no evidence about whether waking sleepwalkers is harmful or not, though the sleepwalker is likely to be disoriented if awakened because sleepwalking occurs during the deepest stage of sleep.
Unlike other sleep disorders, sleepwalking is not associated with daytime behavioral or emotional problems—this may be because the sleepwalker’s sleep is not disturbed—unless they are woken, they are still in a sleep state while sleepwalking.
Maintaining the safety of the sleepwalker and others and seeking treatment for other sleep problems is recommended. Reassurance is recommended if sleepwalking is not causing any problems. However, if it causes distress or there is risk of harm, hypnosis and scheduled waking are recommended as treatments.
For those whose sleepwalking episodes turn to be hazardous, a door alarm may offer a measure of protection. There are various kinds of door alarms that can attach to a bedroom door and when the door is opened, the alarm sounds off. The intention is that the sound will fully awaken the person and interrupt the sleepwalking episode, or if the sleepwalker lives with others, the sound will prompt them to check on the person.
Sleepwalkers should aim to have their bedrooms on the first floor of a home, apartment, dorm, hotel, etc.
Also, sleepwalkers should not have easily accessible weapons (loaded guns, knives) in the bedroom or any room of the house for that matter. If there are weapons, they should be locked away with keys secluded from the sleepwalker.
The lifetime prevalence of sleepwalking is estimated to be 4.6%–10.3%. A meta-analysis of 51 studies, that included more than 100,000 children and adults, found that sleepwalking is more common in children with an estimated 5%, compared with 1.5% of adults, sleepwalking at least once in the previous 12 months. The rate of sleepwalking does not vary across ages during childhood.
Sleepwalking has attracted a sense of mystery, but it had not been seriously investigated and diagnosed until the 19th century. The German chemist and parapsychologist Baron Karl Ludwig von Reichenbach (1788–1869) made extensive studies of sleepwalkers and used his discoveries to formulate his theory of the Odic force.
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.
In 1907, Sigmund Freud spoke about sleepwalking to the Vienna Psychoanalytic Society (Nunberg and Federn). He believed that sleepwalking was connected to fulfilling sexual wishes and was surprised that a person could move without interrupting their dream. At that time, Freud suggested that the essence of this phenomenon was the desire to go to sleep in the same area as the individual had slept in childhood. Ten years later, he speculated about somnambulism in the article “A Metapsychological Supplement to the Theory of Dreams” (1916–17 ). In this essay, he started to clarify and expand his hypothetical ideas on dreams. The dreams is a fragile equilibrium that is only partially successful because the repressed unconscious impulses of the unconscious system. This does not obey the wishes of the ego and maintain their countercathexis. Another reason why dreams are partially successful is because certain preconscious daytime thoughts can be resistant and these can retain a part of their cathexis as well. It is probable how unconscious impulses and day residues can come together and result in a conflict. Freud then wondered about the outcome of this wishful impulse which represents an unconscious instinctual demand and then it becomes a dream wish in the preconscious. Furthermore, Freud stated that this unconscious impulse could be expressed as mobility during sleep. This would be what is observed in somnambulism, though what actually makes it possible remains unknown.
Society and culture
Sleepwalking can sometimes result in injury, assault, or the death of someone else. A model that considers a combination of biological, psychological and social factors has been proposed to explain violent behaviour during sleepwalking. The model has yet to be tested empirically, but if proven, may provide directions for prevention and treatment for at risk sleepwalkers.
Because these sleepwalking behaviours occur without volition, sleepwalking can be used as a legal defense. However, sleepwalking is a difficult case to prove. It is impossible to prove absolutely that a crime occurred in the context of a sleepwalking episode because there is no objective means to assess it retrospectively. It relies on probability and circumstantial evidence of a behavior that often has no witnesses (including the defendant, because amnesia is a feature of sleepwalking). Even a history of sleepwalking does not support that it was a factor during any given event.
Alternative explanations, such as malingering and alcohol and drug-induced amnesia, need to be excluded. 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.” 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.”
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.
Other examples of legal cases involving sleepwalking in the defense include:
- 1846, Albert Tirrell used sleepwalking as a defense against charges of murdering Maria Bickford, a prostitute living in a Boston brothel.
- 1981, Steven Steinberg, of Scottsdale, Arizona was accused of killing his wife and acquitted on the grounds of temporary insanity.
- 1991, R v Burgess: Burgess was accused of hitting his girlfriend on the head with a wine bottle and then a video tape recorder. Found not guilty, at Bristol Crown Court, by reason of insane automatism.
- 1992, R. v. Parks: Parks was accused of killing his mother-in-law and attempting to kill his father-in-law. He was acquitted by the Supreme Court of Canada.
- 1994, Pennsylvania v. Ricksgers: Ricksgers was accused of killing his wife. He was sentenced to life in prison without parole.
- 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 convicted of first-degree murder and sentenced to life with no possibility of parole.
- 2001, California v. Reitz: Stephen Reitz killed his lover, Eva Weinfurtner. He told police he had no recollection of the attack but he had “flashbacks” of believing he was in a scuffle with a male intruder. His parents testified in court that he had been a sleepwalker since he was a child but the court did not buy it and convicted Reitz of first-degree murder in 2004. 
- 2008, Brian Thomas was accused of killing his wife while he dreamt she was an intruder, whilst on holiday in West Wales. Thomas was found not guilty.
In the Malcolm in the Middle season 6 episode “Hal Sleepwalks”, Reese takes advantage of Hal’s sleepwalking by having him do things for Reese, only to learn how much he fears Malcolm’s genius despite loving him.
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