Sleepwalking, or somnambulism, is perhaps the best-known arousal disorder. Sleepwalkers are usually children, although the disorder can occur in adults. Somnambulism may be caused by a number of factors, including stress, fatigue, sleep deprivation and medication.

Incidence rates vary: some people experience less than one nighttime event a month, while the most seriously affected may have nightly events. Children are more likely to be affected than adults, and boys are affected more often than girls.