Science of Sleepwalking

Sleepwalkers have been known to cook while asleep and even commit murders. FirstScience investigates why people sleepwalk.

There are countless stories of sleepwalkers suddenly waking up and finding themselves naked in their backyards. Between 1 and 15% of the population are prone to sleepwalking, which involves people getting up and walking around  while asleep and often doing bizarre things. Frequent sleepwalking can lead to health problems since it interrupts normal patterns of sleep. But what causes sleepwalking and are there ways to control it?

Why do people sleepwalk? Scientists are stil investigating the specific pathways and processes involved.

Possible causes

Sleepwalking occurs in the deep stage of sleep when slow brain waves begin to appear. It is one of a group of disorders known as parasomnias: unusual behaviours or activities that occur during sleep. These range from teeth grinding and restless leg syndrome to having sex or eating while asleep.

But when you get down to what drives these bizarre behaviours, the science gets slightly hazy. Sleepwalking has long been considered a disorder linked to parts of the brain that control arousal, however, the specific pathways and processes involved are still unknown.

Our bodies function according to a 24 hour cycle called a circadian rhythm, where brain wave activity and hormones fluctuate partly under the influence of external factors such as light, but also due to internal regulation. Some researchers believe that slight differences in this cycle could be linked to sleepwalking.

Sue Wilson, a Research Fellow in Psychopharmacology at the University of Bristol in the UK, runs a sleep clinic and is investigating the causes of sleepwalking. Her research has focused on the link between stress hormones and parasomnias. "We think that perhaps sleepwalkers have different circadian rhythms of stress - they're more stressed after a night's sleep than normal sleepers," she says. A sleepwalker's stress levels can get even higher when they become concerned about their sleepwalking. "It's a vicious circle," says Wilson, "they worry about sleepwalking so they have insomnia. And of course, if you sleep deprive yourself you go into a deeper sleep and so you're more likely to sleepwalk."