While sleeping overnight at a hotel in 2006, Canadian tennis star Peter Polansky saw a dark figure with a knife standing by the doorway to his room. Still asleep, the 17-year-old athlete bolted out of bed, and in an effort to escape the phantom intruder, kicked the glass out of his window and jumped out. He plummeted three stories and landed in a courtyard, miraculously escaping death.
Though stories like these are rare, as many as 9 percent of adults are affected by so-called parasomnias, in which a person, technically asleep, engages in complex and bizarre activity. Parasomnias come in many forms, among them sleepwalking, sleep talking, and night terrors. Researchers still do not understand the origins of these odd behaviors. With rare exceptions, no one has been able to trace parasomnias to an obvious problem, such as an anatomical fault or chemical imbalance in the brain. Nonetheless, sleep disorder experts have been able to provide some help, mostly through the use of sedative drugs.
Although many parasomnias are exotic, one is very familiar: sleep talking. As anyone privy to such utterances knows, people who talk in their sleep rarely generate complete sentences, and the strings of words often make no sense. “Even in a sleep lab,” says Mark Mahowald, a sleep expert and professor of neurology of the University of Minnesota, “we’ve never picked up someone expounding at length on any topic.”
Sleepwalking is also common and well known. Here, too, the normal daytime activity is garbled and distorted. A typical sleepwalking episode in an adult man might lead him to get up because of a full bladder, take a wrong turn, go to the closet, and urinate in a shoe. A woman might instead sit down and urinate in a wastepaper basket. Other frequently reported variations of sleepwalking include moving furniture around, banging on the piano, or going for a stroll.
People even have sex during sleep (for firsthand accounts, go to www.sleepsex.com). To be sure, this behavior has not been documented in a laboratory setting, where people sleep solo. Still, researchers deem these stories highly credible. In most of these anecdotes, the behavior is initiated by the man—his partner may find out only later that he was asleep during the event. Experts say snoring during sex—they jest not—is a tip-off.
We may walk or talk in our sleep at any age, but sleep terrors, another form of parasomnia, particularly afflict children. During these distressing episodes, the sleeper sits up in a panic and may launch into piercing screams, usually sweating and breathing heavily, with eyes wide open and pupils dilated. He or she may thrash around or bolt out of bed. During such episodes, both children and adults are often inconsolable and impossible to awaken. “All you can do is direct them back to bed, and they usually will calm down on their own after a few minutes,” says David Neubauer, associate director of the Sleep Disorders Center at the Johns Hopkins University School of Medicine. Why children are especially prone to this problem is unclear. “If you simply sit a child up in bed, it’s much easier to induce sleepwalking than in an adult,” says Jerome Siegel, professor of psychiatry at the University at California at Los Angeles.
Someone waking up from a nightmare can usually describe a complex plot. Night terrors, on the other hand, have no narrative—they are an experience of fear, pure and simple. People rarely recall anything. When they do, says Neubauer, “they report a crystallized sense of something terrible about to happen.” This frequently takes the form of a single fragmentary image—a monster face, a collapsing ceiling, or engulfing flames. “One man in the midst of a sleep terror bolted out of bed, grabbed his baby from the crib, and ran out of the house,” says Neubauer. “He thought a bomb was about to go off.”
Although sleepwalkers may appear to be dreaming, this is rarely the case, laboratory studies have shown. That’s because rapid eye movement (REM) sleep, when we dream, also paralyzes our limbs, Siegel explains. As REM sleep begins, the cortex becomes as active as when we’re awake—a sign that our imaginations are running riot in those fits of nightly madness we call dreaming. Yet the pons, an area of the brain just above the spinal cord, prevents motor neurons, the controllers of muscles, from activating movements. We are rendered as limp as wet noodles as we dream away, prevented from screaming or thrashing about no matter how intense our dreams become.
In non-REM sleep, by contrast, our muscles are functional, although people who walk or talk while asleep are a bit like automatons: They have no conscious awareness, and most have total amnesia about such episodes. “Sleep is not a whole-brain phenomenon,” explains Mahowald. “Part of your brain may be awake enough to engage in complicated behaviors while other parts are asleep, so you’re not aware of what you’re doing or responsible for your actions.”
That’s important to bear in mind, he says, since on rare occasions, parasomnias take a dangerous turn. Sleepwalkers have been known to switch on stoves and cook, fall off balconies, and even get behind the wheel of a car. Some deaths classified as suicides result from circumstances similar to the ones that preceded the near-fatal fall of tennis star Peter Polansky, Mahowald believes.
A physical cause has been uncovered for one rare sleep disorder, known as REM sleep behavior disorder. This parasomnia is believed to arise from damage to pathways that block motor impulses to the limbs during REM sleep. As a result, the sleeper’s muscles are not paralyzed during REM, and she or he may literally “act out” dreams.
An individual with REM sleep behavior disorder may dream of being in a fight and slam his fist into the bedside table, says Helene Emsellem, medical director of the Center for Sleep and Wake Disorders in Chevy Chase, Maryland. In one case reported in the medical literature, a man dreamed that he was trying to snap the neck of a deer and woke up to his wife’s screams in response to his hands wrenching her neck. “When someone is prone to REM-related behavioral disorder, I often caution their sleep partners to get out of bed, turn on the lights, and call from the doorway,” says Emsellem, author of Snooze . . . or Lose!, a book on improving teenagers’ sleep habits. “Otherwise, there’s the danger that the partner will be incorporated into the dream and could be injured.” Mahowald believes people with this disorder may even be capable of killing in their sleep, although he’s the first to admit that it would be impossible to prove after the fact.
Why are some people more prone to parasomnias than others? Sleep apnea, in which breathing repeatedly stops during the night, is correlated with an increased incidence of REM sleep behavior disorder. Sleep deprivation due to jet lag or shift work is also a well-known trigger of all sorts of parasomnias. Genetics may also contribute, since the problems often run in families. Yet another cause may be alcohol or, paradoxically, sleep-promoting agents like Ambien, Halcion, and Restoril. Indeed, the Food and Drug Administration recently warned that in some cases, these drugs may be linked to sleep driving. Representative Patrick Kennedy, Democrat of Rhode Island, blamed Ambien when he crashed his car near the nation’s capital last year.
The good news is that benzodiazepines, a class of tranquilizing compounds, can often curb sleepwalking urges and related parasomnias. But psychotherapy may not help. “Contrary to popular perception,” says Mahowald, “the vast majority of parasomnias are unrelated to any kind of psychiatric disturbance.”
Fortunately, even in someone prone to sleepwalking, violent or self-injurious behaviors while asleep tend to be isolated events, never to be repeated. By the same token, that’s what makes them so scary. Despite technology that allows us to peer inside the brain, such episodes are not only mystifying but also—in Mahowald’s words—“frighteningly unpredictable.”