Sleepwalking, or somnambulism, is one of the most striking arousal disorders, if only because it can scare other members of the household. Like many parasomnias, the causes of somnambulism are a mystery even to scientists. It is believed that the condition can be aggravated by stress, fatigue, sleep deprivation and some medications. Sleepwalking most often occurs during deep sleep (stage 3) early in the night. (Another scientific name is noctambulism.)
Sleepwalking more often happens in children (most often in ages 6 to 12, more often in boys than girls). It used to be thought rare in adults, but a Stanford study released in 2012 estimated that 3.6% of American adults have sleepwalked in the past year. Indeed, kids who have somnambulism are more apt to experience night terrors, which has led some experts to suggest that the two are related. People who sleep "deep" (spend a lot of time in Stage 3) are more likely to experience both sleepwalking and night terrors. Sleepwalkers have different patterns with some individuals only walking a few times a year and others almost every night. Sleepwalking appears to run in families. This sleep disorder affects an estimated 10 percent of all people at least once in their lives.
Sleepwalkers have no memory of their excursions when they awake. They have open eyes and blank expressions, and cannot be easily awoken while walking. When they are awoken, they are often confused. Measured EEG activity shows different brain patterns in recently awoken sleepwalkers. Children sometimes urinate during their sleepwalking and somnambulants sometimes talk.
Sometimes the person just sits up in bed and appears awake before lying down again. More dangerous behavior including cooking and driving have also been recorded. People often injure themselves during walking episodes, especially through falling down or tripping. There is an urban myth that it is dangerous to awaken a sleepwalker, and while waking someone up when they are in a sleepwalking state might cause them stress, it is not true that the shock would kill them. It is usually more dangerous to let them walk while sleeping, given the potential for injury.
The cause of sleepwalking is not known, but it has been proposed that a sudden arousal from NREM sleep is the cause. Both sleepwalking and night terrors are most likely early in the night, during the first episode of slow wave sleep.
In bad cases when conditions warrant, doctors sometimes prescribe a benzodiazepine for sleepwalking, but this type of medication has side effects and most doctors are reluctant to prescribe it unless the condition is particularly dangerous. Hypnosis is also used sometimes.
The more common way to deal with sleepwalking in children is to let them outgrow it. During the period when they experience sleepwalking, and for adults with the condition, you can help them by encouraging good sleep hygiene, keeping the floor picked up to eliminate tripping hazards, locating the bedroom on the ground floor, and locking doors and windows. More on kids getting to sleep.
A famous sleepwalking depiction was in Shakespeare's MacBeth, Act 5, Scene 1. While good theater, and perhaps decent pop psychology, this scene is not an accurate representation of sleepwalking. Lady MacBeth plays out actions related to the story and her own guilt in murders. This was often represented as a woman's "hysteria" which has also been discredited as a common psychological problem.
(Trivia: Dymphna, a 7th Century Irish woman, is the patron saint of sleepwalkers.)