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, violent gestures, or even homicide. Other activities that may attend sleepwalking include: moaning, talking, gesturing, and grabbing at apparently hallucinated objects. 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 a 30 seconds or as long as 30 minutes.
Sleepwalking has always 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 sleep (rapid eye movement) 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.
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's no recorded preference to male or female individuals. 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 hypnosis can also cause sleepwalking to occur.