Sleep walking often runs in families. It occurs during partial arousal from stage 4 sleep in which the sleeper does not come to full consciousness. There is usually no memory of the episode the following day.

Most cases begin in childhood and are attributed mainly to delayed development of the nervous system, and the child usually grows out of it by adolescence. Sleep walkers usually have their eyes open and shuffle about. They have poor coordination and unintelligible speech during the episode.

An EEG recording during an episode with show a combination of delta waves (indicating deep sleep), and alpha and beta waves (indicating a waking state). Sleep walkers are awake enough to do tasks that do not require their full attention and asleep enough to not remember doing the tasks. Due to their reduced coordination, safety is a major concern. Sleepwalkers have been known to walk through windows, drive, fall down stairs, etc.

Sleep walking episodes in adults usually happen during periods of major stress and are more likely to be associated with psychiatric disorders. It is not dangerous to wake a sleep walker, but experts say simply guiding them back to bed is the best course of action.