How Sleepwalking Works

By: Katie Lambert  | 
A man sleepwalking into the lawn.
Sleepwalking is a strange phenomenon that is classified as parasomnia. Betsie Van der Meer / Getty Images

Key Takeaways

  • Sleepwalking, or somnambulism, is characterized by walking or performing other complex behaviors while in a state of partial arousal from deep, non-REM sleep.
  • Sleepwalking occurs during deep sleep stages. It involves a disconnect between brain functions, where the brain is less active but the body can still move.
  • Factors contributing to sleepwalking include genetics, sleep deprivation, stress and some medications.

Sleepwalking is an intriguing phenomenon. The fact that you're sleeping while performing physical feats is pretty amazing. How can a person be unconscious but still coordinate his or her limbs in order to walk, talk and, sometimes, even drive? How do we know when we're really awake?

Doctor: You see, her eyes are open. Gentlewoman: Ay, but their sense is shut. — Macbeth, Act V Scene 1

Sleepwalking is also known as somnambulism, so add that to your SAT vocab. It's classified as a parasomnia, an abnormal behavior during sleep that's disruptive. Common parasomnias include bed-wetting and teeth grinding. Drs. Hobson and Silvestri describe parasomnias as "errors in timing and balance" in the brain as it transitions between waking and sleeping [source: sleepwalking5.htm">Hobson].


Think of how complex the brain is and how many tasks it performs: It keeps you breathing, it reminds your heart to beat, it records all the memories of your life, and it enables you to laugh, cry, love and converse. Now think of how you sleep, how your body moves from dreams to no dreams and back again, how you might steal covers from your partner or snore or move around, how sometimes you wake up rested and other days you wake up anxious. It's a complex process controlled by a complex organ: There's plenty of room for glitches.

What makes a sleeping body rise? People used to think that sleepwalkers were acting out their dreams and subconscious desires and fears. Take Shakespeare's Lady Macbeth, who during the day conceals the depth of her treachery, but at night in her sleep confesses her guilt. Others associate it with the occult, as in "Dracula" when the vampire is finally able to sink his teeth into Lucy while she sleeps. Others insist that it's purely a physical response, illustrated by the case of the title character in Bellini's opera "La Sonnambula," who incurs all sorts of trouble by the innocent actions she performs while she sleeps (more on this later).

In this article, we'll explore the whys of sleepwalking: why it happens the way it does, why it happens at all and why it's so fascinating.


Characteristics of Sleepwalking

An image is projected onto the facade of the Museum of Modern Art during a public art project by artist Doug Aitken in New York City. "Sleepwalkers" explored how people experience memory and narrative in an urban environment.
Spencer Platt/Getty Images

You've probably seen sleepwalkers in the movies traveling down staircases with eyes shut and arms outstretched, but let's learn the facts.

The DSM-IV, a handbook for mental health professionals, defines sleepwalking by these criteria:


  • You leave your bed while sleeping, usually in the first third of your sleep pattern.
  • Others find it difficult to wake you during an episode of sleepwalking.
  • You can't remember what happened while you were sleepwalking.
  • When you do wake up from an episode, you're confused.
  • You aren't suffering from dementia or another physical disorder.
  • It impairs your work or social life.

[source: Szelenberger]

Now let's take a look at some of these criteria. During the first third of the night, your body is in NREM (non-REM) — your deepest stage of sleep. NREM sleep is when you tend to toss and turn in bed. Your brain quiets down, which means that you aren't dreaming. So sleepwalkers aren't acting out their dreams. Think of it this way: In NREM sleep, your brain isn't very active, but your body is. In REM sleep, your brain is very active while your body isn't.

The brain is resistant to arousal during deep sleep, which explains why it's difficult to wake a sleepwalker. And if you do manage to wake one up, the sleepwalker is likely to exhibit signs of confusion for several minutes and have little to no memory of anything that happened.

Sleepwalking episodes can last from a few seconds to half an hour. Sleepwalkers usually have glassy-looking eyes and blank expressions on their faces. They might look awake but act clumsy. Sleepwalkers are capable of performing a variety of activities, from simply getting up and walking around the room to driving a car or playing an instrument.

Sleepwalking occurs most often in children, and more commonly in boys than in girls.
Sarma Ozols/Getty Images

Sleepwalkers are most often children. Lots more people than you realize have stories about sleepwalking when they were kids — their parents found them wandering on the front lawn, or they walked down the street in their pajamas. Kids tend to grow out of it. The adult population of sleepwalkers is much smaller. Sleepwalking also runs in families, and occurs more often in boys than in girls.

So now to the million-dollar question: Why do some of us get up and walk around in the middle of the night?


Why Do People Sleepwalk?

Sleep stages

People used to think that sleepwalkers acted out their dreams. They also thought that sleepwalking had to do with epilepsy, hysteria, dissociative disorders or even your own secret wishes.

To be perfectly honest, no one knows exactly why people sleepwalk, but we'll talk about some possibilities.


We've mentioned that sleepwalking occurs during your deepest stages of sleep, stages 3 and 4, when brainwaves are very slow. During the day, your brain is a beehive of activity — during NREM sleep it is barely humming. Your body, however, is still active, and hasn't completely quieted down for the day. So what we have here is a body that can still move, paired with a sleepy brain.

Mental health professionals refer to sleepwalking as a "disorder of arousal," which means that something triggers the brain into arousal from deep sleep, so the person is in a transition state between sleeping and waking.

The fact that most sleepwalkers are children is significant, especially since most of them grow out of it. A child's brain develops very quickly and is primed to soak up all kinds of stimuli. Drooling babies grow into reading kindergartners in five years — do you think you'll experience the same kind of brain development in the next five years?

Some suggest that a child's brain is simply too immature to completely understand the cycles of waking and sleeping — think of sleep as having fuzzy borders. Other propose that since children develop so quickly, perhaps some areas of the brain outpace others in development, or certain aspects of development take precedence.

NREM sleep is also when your body repairs itself and releases hormones, including growth hormones. Children spend a lot of their time growing, and it's possible that the release of hormones has something to do with triggering arousal from sleep.

Most adult sleepwalkers also sleepwalked as children — it rarely begins in adulthood except as a symptom of another disorder. Children tend to sleepwalk more when they are overly tired or stressed. The same factors affect adults, as well as certain medicines, alcohol and fever illnesses.

Of course, in some people, sleepwalking isn't so harmless. Sleepwalking has been linked to seizures, REM sleep disorders and organic brain disorders like Parkinson's and Alzheimer's. If your child is sleepwalking, he or she will probably either grow out of it or can be helped by a regular sleep schedule and some stress reduction. If you're an adult and start sleepwalking, it might be a good idea to talk to a doctor.


Sleepwalking and the Arts

Circa 1865: Italian-born British operatic soprano Adelina Patti in the opera "La Sonnambula"
Hulton Archive/Getty Images

Sleepwalking is a popular phenomenon to depict within the arts, possibly because it's a way to explore boundaries and convey psychological elements. Shakespeare, for one, used a sleepwalking scene in "Macbeth" to expose a key element in Lady Macbeth's character development. Her ruthless ambition leads her to concoct a murder plot — only it turns out that she doesn't have the stomach for it. Her gentlewoman brings a doctor to see Lady Macbeth as she walks the castle in her sleep, confessing her sins and attempting to wash the blood from her hands. Sleep takes away the mask she wears during the day and calls forth her confessions without her permission — the sleeping body rebels against the waking mind.

In Bellini's opera "La Sonnambula," a sleepwalking incident leads to chaos. A sleepwalking woman is accused of being unfaithful to her husband when she innocently awakens in another man's room. In the opera, the other characters only believe the sleepwalker's story when they see her walking along a high bridge. They don't wake her because the shock might cause her to fall and perish. Her innocence is proven only by her proximity to danger. This is the sort of instance that maybe gave rise to the myth that waking a sleepwalker is harmful.


1958: Nina Vyroubova and Serge Golovine in "The Sleepwalker," by International Ballet of the Marquees de Cuevas­
Lipnitzki/Roger Viollet/Getty Images

Legendary choreographer George Balanchine's ballet "La Sonnambula" uses some of Bellini's music, but changes the story. The ballet tells the tale of a poet who attends a baron's ball, meets a beautiful sleepwalker and is murdered by the host of the ball in a fit of jealousy. When the poet encounters the sleepwalker, he can't wake her. After he dies, his body is brought to her to hold. It's interesting to see a ballet that involves sleepwalking, the physical aspect of the sleepwalking is the most important. The ballerina dancing the part of the sleepwalker must perform a complicated pas de deux while making it clear to the audience that she's asleep. The element of sleepwalking adds an eerie, mystical feeling that enhances the darker undertones of the ballet.

A scene from the German silent film "The Cabinet of Dr. Caligari," directed by Robert Wiene
Hulton Archive/Getty Images

"The Cabinet of Dr. Caligari" is possibly the world's first horror movie, and its plot centers on the idea of a murdering sleepwalker controlled by an evil doctor. The film's German Expressionist style helps set the tone for madness and sinister forces, with dramatic shadows and warped-looking sets. In "Dracula," the vampire is finally able to sink his teeth into Lucy during a bout of sleepwalking.

In the arts, sleepwalking is linked to blood, danger and the occult, but most of all, loss of control. Sleepwalkers cede their fate to the hands of those around them. Part of the fascination with sleepwalking might be because it involves a state of transition, a person with his or her feet in two different spheres, straddling the border. Part of it is also fear — what fantasies or dark deeds might you act in your sleep, unbeknownst to yourself? What if your body roams the night, but leaves its soul and mind behind? Sleepwalking has a zombie-like component to it.


Other Parasomnias

Sleep-eating is one side effect of Ambien.
© Blasius Erlinger/Getty Images

Sleepwalking isn't the only parasomnia. There's also sleepsex, sometimes called sexsomnia or SBS (somnambulistic sexual behavior). It's pretty much what it sounds like — sexual behavior during sleep. People with this condition might touch themselves sexually or initiate sex while asleep. They only know it happened when their roommate or partner mentions the incident. One man was actually acquitted of rape after using the defense that he was asleep at the time of the assault [source: The Independent]. People with sexsomnia tend to be sleepwalkers or have other parasomnias.

Just as disconcerting? Sleep-eating. You might associate sleep eating with the sleep aid Ambien. As the drug grew in popularity, stories began to crop up about people eating in their sleep. And not just getting up for a sandwich — eating from tubs of margarine or eating cigarettes and raw meat. People wake up with crumbs in the bed or start putting on the pounds and have no idea why. They might come into the kitchen only to find tortilla chips all over the counters and cheese on the floor — sloppy preparation seems to be a hallmark of sleep-eating. Ambien outsells all other RX sleep aids in its class, despite the possible strange side effects [source: NY Times]. Some people report that the problem stops after they switch to another drug, and that Ambien itself is the problem. Some doctors say that sleep-eating might just be another symptom of whatever's causing your sleepwalking in the first place.


Some people clench or grind their teeth while they sleep, a condition called bruxism. The grinding noise can be loud enough to wake up your sleeping partner — some people say it sounds like the person is chewing rocks. It can damage the teeth, give you headaches and make your jaw hurt. If you're awake and grinding your teeth, you'll notice when it starts to hurt and you'll stop, but when you're asleep, the body isn't as attuned. One doctor claims that sleep bruxism results in 250 lbs. of pressure on the tooth [source: NY Times]. Stress makes bruxism worse, and some doctors recommend anti-anxiety medications for strong cases, although a special mouthguard should help.

Sleep bruxism could result in 250 pounds of pressure on the tooth.
Holloway/Getty Images

Sleep talking, sometimes called somniloquy, might wake up the person next to you, but it's harmless. Someone who sleep talks might just make noises, or could have a long one-sided conversation with you. Sleep enuresis is a fancy term for bed-wetting. REM sleep behavior disorder (RBD) is a bit like sleepwalking, only someone with RBD is acting out during REM sleep, the stage where your muscles shouldn't be moving at all. RBD usually results in people acting out their dreams, like the false perception people have of sleepwalking.

For more information on sleep and sleep disorders, check out the links that follow.


Frequently Asked Questions

What triggers sleepwalking episodes?
Sleepwalking episodes can be triggered by sleep deprivation, stress, fever and certain medications.
Can sleepwalking be cured?
While there's no cure for sleepwalking, managing stress, maintaining a regular sleep schedule and minimizing sleep disruptions can reduce the frequency of episodes. In some cases, medication may be prescribed to manage underlying conditions.

Lots More Information

Related Articles

More Great Links

  • "Ambien May Prompt Sleep Eating." CBS News. March 15, 2006.
  • Blakey, Rea. "Sleep eating - a behavioral food fight." July 2, 2002.
  • "The Boston Tragedy: Tirrell Murdering Mary Ann Bickford." National Police Gazette, 1846. The History Project, University of California, Davis.
  • Chan, Allison and Christian Guilleminault. "Review of Somnambulism in Children." Current Pediatric Reviews. 2005, Vol. 1 No. 2.
  • DeNoon, Daniel J. "Ambien Linked to 'Sleep Eating.'" WebMD. March 15, 2006.
  • "Do not scorn her with words fierce and bitter: Maria Bickford." An exhibition from the collections of the John Hay Library. Brown University Library. 1996.
  • Fenwick, Peter. "Somnambulism and the Law: A Review." Behavioral Sciences & the Law. 1987. Vol. 5, No. 3, p. 343-357.
  • Hobson, J. Allan and Lia Silvestri. "Parasomnias." Harvard Mental Health Letter. Feb. 1999.
  • Improving Sleep: A Guide to Getting a Good Night's Rest (2005); 2005, p34-353, 2p. Harvard Health Publications
  • Juan, Dr. Stephen. "What is sexsomnia?" The Register. Feb. 3, 2007.
  • Kisselgoff, Anna. "Ballet: 'La Sonnambula.'" The New York Times. July 8, 1983.
  • MacDonald, Ann. "Brain Development in Childhood." The DANA Foundation. November 2007.
  • Plazzi, G., et al. "Sleepwalking and other ambulatory behaviours during sleep." Neurological Sciences. Dec2005 Supplement 3, Vol. 26, ps193-s198, 6p
  • "Repertory Index: La Sonnambula." New York City Ballet.
  • Sample, Ian. "Why do people sleepwalk?" The Guardian. March 24, 2005.
  • Saul, Stephanie. "Study Links Ambien Use to Unconscious Food Forays." New York Times. March 14, 2006.
  • Schadler, Jay. "Sleeping with the Enemy." ABC News. July 26, 2006.
  • Smith-Spark, Laura. "How sleepwalking can lead to killing." BBC News. March 18, 2005.
  • Szelenberger, Waldemar, Szymon Niemcewicz and Anna Justyna Dabrowska. "Sleepwalking and night terrors: Psychopathological and psychophysiological correlates." International Review of Psychiatry. August 2005; 17(4): 263-270
  • Van DeCaar, Paul. "A Lineman in My Bed: Notes on Teeth Grinding." New York Times. Nov. 13, 2007.
  • Wenner, Melinda. "Study: 'Sexsomnia' Causes People to Have Sex in Their Sleep." FOX News. June 5, 2007.,2933,277373,00.html