Sleepwalking is often fodder for movie plots. For instance, in the comedy Step Brothers, Will Ferrell and John C. Reilly play a pair of adult siblings whose sleepwalking antics include eating coffee grounds, dismantling the Christmas tree, and pummeling the person who tried to wake them up. But in real life, sleepwalking isn’t quite so entertaining.

What Is Sleepwalking?

Sleepwalking, technically called “somnambulism,” is an abnormal sleep behavior that causes people to get up and move around while they’re still asleep. Sleepwalking affects a surprisingly large number of people, with about 30 percent of adults reporting at least one somnambulant episode in their lifetime, and just over 3.5 percent–a whopping 8.4 million people–suffering from sleepwalking on a regular basis.

It’s more common in children than adults, and those who are prone to it find that sleep deprivation can trigger a sleepwalking event. Contrary to its name, the disorder is not limited to just walking in one’s sleep. Somnambulant behaviors can range from simply sitting up and talking in bed to performing complex tasks, like drawing or cooking.

What Causes It?

The root cause of many cases of sleepwalking remains a mystery. Certain medications, particularly some used to treat insomnia, list sleepwalking as a potential side effect. Stress and sleep deprivation can cause somnambulance, and people with depression, obsessive-compulsive disorder, and alcohol dependency are more likely than others to have sleepwalking episodes.

How Should You Wake a Sleepwalker?

Prevailing wisdom is that it’s not safe to wake a sleepwalker, but this is not entirely true. Waking someone from a somnambulant episode won’t cause them to have a stroke, coronary, or panic attack, but it is possible that they could become physically violent and injure the person trying to wake them.

Sleepwalking most often occurs during deep sleep–a sleep stage called non-REM 3–and a person waking from this stage is going to be cognitively impaired for up to half an hour. This can cause them to be confused or agitated, and they may not even recognize the person trying to wake them, initiating a fight-or-flight response.

So can you wake up a sleepwalker safely? The National Sleep Foundation recommends gently guiding them back to their bed, trying not to wake them and touching them as little as possible. If you absolutely must wake a sleepwalker, make loud noises from a safe distance. Once they’re awake, explain that they’ve been sleepwalking and wait until you’re sure they are calm and coherent before approaching.

Safety Measures for Sleepwalkers

Sleepwalking can be a dangerous activity, and not just for the poor soul trying to wake a zombie. Sleepwalkers have fallen out windows, strolled into traffic, succumbed to hypothermia, and even committed murder while unconscious. Somnambulance is particularly dangerous for children.

If you or a family member suffer from this disorder, check into safety devices such as door alarms for sleepwalkers to help prevent accidents. Motion detectors and bed alarms are other types of sleepwalking alarms on the market that can either wake the sleeper before they hurt themselves or alert their caregivers (in the case of children or dementia patients, for example) who can get the sleepwalker safely back to bed. Other safety devices, like bed rails and gates at the stairs, may also help circumvent unwanted nocturnal adventures.

If the sleepwalking is caused by an underlying medical problem, such as depression, treatment for the illness often curbs the somnambulance as well. Therapy, meditation, and prescription medication have proven successful in treating many cases of sleepwalking.