Sleepwalking (also called somnambulism or noctambulism) is a parasomnia or sleep disorder where the sufferer engages in activities that are normally associated with wakefulness while he or she is asleep or in a sleep-like state. Sleepwalking is usually defined by or involves the person affected apparently shifting from his or her prior sleeping position and moving around and performing normal actions as if awake (cleaning, walking and other activities). It is inexact to assume that somnambulists are unconscious during their nocturnal sleepwalking episodes. They are simply not conscious of their actions on a level where memory of the sleepwalking episode can be recalled, and because of this, unless the sleepwalker is awakened or aroused by someone else, this sleep disorder can go unnoticed. Sleepwalking is more commonly experienced in people with high levels of stress, anxiety or psychological factors and in people with genetic factors (family history), or sometimes a combination of both.

A common misconception is that sleepwalking is acting out the physical movements within a dream, but in fact, sleepwalking occurs earlier on in the night when rapid eye movement (REM), or the "dream stage" of sleep, has not yet occurred.


Sleepwalking can affect people of any age. It generally occurs when an individual moves during slow wave sleep (during stage 3 or 4 of slow wave sleep—deep sleep) (Horne, 1992; Kales & Kales, 1975). In children and young adults, up to 80% of the night is spent in SWS (50% in infants). However, this decreases as the person ages, until none can be measured in the geriatric individual. For this reason, children and young adults (or anyone else with a high amount of slow wave sleep [SWS]) are more likely to be woken up and, for the same reasons, they are witnessed to have many more episodes than the older individuals.


According to a Finnish study published in 1997, children sleepwalk more frequently than adults. Sleepwalking was reported for 6.9% of female children and 5.7% of male children, compared to rates of 3.1% for adult women and 3.9% for adult men.

Activities such as eating, bathing, urinating, dressing, driving cars, whistling, dancing, committing murder, and engaging in sexual intercourse have been reported or claimed to have occurred during sleepwalking. Contrary to popular belief, most cases of sleepwalking do not consist of walking around (without the conscious knowledge of the subject). Most cases of somnambulism occur when the person is awakened (something or someone disturbs their SWS); the person may sit up, look around and immediately go back to sleep. But these kinds of incidences are rarely noticed or reported unless recorded in a sleep clinic.

Sleepwalkers engage in their activities with their eyes open so they can navigate their surroundings, not with their eyes closed and their arms outstretched, as often parodied in cartoons and films. The subject's eyes may have a glazed or empty appearance, and if questioned, the subject will be slow to answer and may be unable to respond in an intelligible manner.


When sleepwalkers are a danger to themselves or others (for example, when climbing up or down steps or trying to use a potentially dangerous tool such as a stove or a knife), steering them away from the danger and back to bed is advisable. It has even been reported that people have died or were injured as a result of sleepwalking.. Sleepwalking should not be confused with psychosis.

Sleepwalking has in rare cases been used as a defense (sometimes successfully) against charges of murder (see Homicidal somnambulism).

In art and culture

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.

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 Kabinett des Dr. Kaligari (English title: The Cabinet of Dr. Caligari). In Shakespeare's Macbeth, Lady Macbeth sleepwalks because of her overwhelming guilt and insanity. 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 sex with her ex-husband while sleepwalking and gets pregnant.

Legal defense

In 1846, Albert Tirrell was found not guilty of murder and arson, arguing that if he did do it, he was sleepwalking at the time, the first successful acquittal using a sleepwalking defense in American legal history.

Kenneth Parks, a 23-year-old, drove his car 15 miles to his in-laws' house in May 1987. There, he attacked his father-in-law, leaving him unconscious, and stabbed his mother-in-law, killing her. He then went to the police station saying, "I think I have killed some people." He was bloody, and his hand was badly injured. Parks was unable to recount anything about the murder, and he had no motives for committing them. He was unemployed and stressed. He went to sleep that night thinking about how he was going to visit his in-laws the next day with his wife to tell them about his financial and gambling problems. After a year, he was found not guilty of murder or attempted murder. There was an appeal, but his acquittal was upheld. He did not serve time in a mental ward because "noninsane automatism" (i.e., sleepwalking) is not legally viewed as a mental disorder.

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