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In this exploration of sleepwalking, basic as well as more advanced sleep phenomena are discussed, and the disorder itself is described, including its historical and cultural significance.

A long, varied group of contributing factors are summarized, including such proximal causes as sleep-related seizures, illicit drug use, and medication-induced side effects; longer-term issues, such as insomnia, partial sleep deprivation, and chronic sleep deprivation; hormone levels; psychiatric illness; unusual sleep states, such as nocturnal dissociative states and confusional arousals; and a range of other considerations, such as alcohol abuse and task-specific complex behaviours commonly reported among sleep-disordered professional athletes.

The relationship between sleepwalking and other sleep disorders is considered, as is the relationship between sleepwalking and criminal behaviour. Finally, our field’s current understanding is presented, including the most commonly used assessment tools and recommended treatment algorithms.

Introducing the topic: Sleepwalking, or somnambulism, has a long, rich history replete with literary, mythic, and scientific explorations.

Known to many solely from fictional portrayals of bizarre occurrences – bodies ensnared in peculiar locations, seemingly mindful individuals deemed unconscious, or very rarely, tragic cases in which a person lost his or her life to a strange and inexplicable sleep-related event – sleepwalking is fascinating in the array of questions it poses for modern science.

Anyone who has personally experienced a sleepwalking episode is well aware of how mystifying the behaviour can be. It appears to be continuous unconscious walking; yet, on the surface, the affected individual appears to be conscious to some extent, interacting with his or her surroundings.

Definition and History

Thus, the ancient Greek phrase μεστη γαρ ειναι της φρενος, which occurs in Thucydides and Æschylus, designates the entire mental condition of the noctambulist, and has reference to all mental, and therefore, also, to all physiological aberrations, created either by moral suffering or by disease of the human organism.

On the other hand, in his tragedies, Sophocles occasionally deems it necessary to indicate by special actions the weakened mental capabilities of certain characters, who neither sleep nor wake, and whose sluggishness of mind or, rather, their spiritual drunkenness, often constitutes an essential element of the tragic situation.

These are generally either demented or stupefied, and are incapable of forming sound judgments. In all these cases the local – namely, the practical tendency which appears especially in the actions of men (individuals and communities) – is more prominently brought forward than the personal.

As long as its efforts have not been entirely frustrated, the influence of ‘fate’ disguises itself under various forms, elaborating externally its great work of life, by a continuous but gradually changing division of thought, action, and willing into willingness, doing, and object of the action.

As soon as this division becomes predominant, such men do that which has been termed somnambulistic, or rather, what has been designated as sleep-walking.

The terms somnambulism, noctambulism, and night-walking signify the peculiar phenomenon in question. The dictionary gives, as the primary meaning of ‘somnambulism,’ the act of walking in one’s sleep, and, as a secondary meaning, a condition of which the chief characteristic is an apparent intermediate state between sleeping and waking.

The current popular idea of the sleepy wayfarer is thus expressed with considerable accuracy, and agrees with numerous experiences of everyday life. Since these walks in his sleep, and, during this condition, is without consciousness, to ‘sleep-walk’ or ‘night-walk’ are well-adapted synonyms.

This wandering from a purely local standpoint, and of wandering in time and knowledge. The approach of various stages of unconsciousness, or, more properly speaking, of the various degrees of activity of the sleeping consciousness, has always appealed to the abstractions of superstitious observers, who, induced to interpret real phenomena in conformity with fantastic dogmas, have ascribed to somnambulism an entirely peculiar nature.


Based on a case-control study performed in 2006, the reported relative risk for children with inadequate sleep who walked in their sleep was 3.5 when compared with control children. Inadequate sleep was also more common in children (2–14 years of age) who sleepwalked in an Australian study performed in 2008.

Behavioural episodes during sleep can be triggered by modifiable risk factors, with the potential benefit of improving the quality of sleep.

Among adults who were admitted to a sleep clinic, 17.2% reported at least one episode of somnambulism during their lifetime. There is a major increase in the prevalence of somnambulism during prepubescent years with decreased frequency after puberty.

The prevalence in adults (0.5–4.0%) is slightly greater than other extremely complex behaviours such as night terrors. Despite self-limited status, somnambulistic events are potentially harmful, with a reported rate of injury ranging from 2.7 to 26.6% of frequent somnambulists sleeping alone.

Somnambulism is a major factor in family discord, and, in most episodes, it serves as a trigger for medicolegal interactions.


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