Sleep is mysterious. Every animal on the planet needs it, but each one does it a little differently—and scientists still don’t know why sleep is so important. So it’s even more puzzling when sleep doesn’t go as it should. Difficulty sleeping affects nearly all of us at one time or another. According to the Centers for Disease Control and Prevention, more than a third of Americans are not getting enough sleep, and the American Sleep Association reports that between 50 and 70 million Americans suffer from sleep disorders.
Insomnia and sleep apnea are two of the most common sleep disorders, but there are other, lesser-known conditions that can be as baffling as the phenomenon of sleep itself. They are grouped under the category of parasomnias, or abnormalities in sleep behavior, and can range from merely annoying to the positively frightening. Here’s a look at four of the most unusual: exploding head syndrome, sleepwalking, sleep paralysis, and catathrenia (sleep groaning). (What follows should not be construed as medical advice—if you think you might have a sleep disorder, talk to your doctor!)
Exploding head syndrome
With one of the most unnecessarily alarming names for a medical condition in history, exploding head syndrome is not what it sounds like—although sound does play a key role. Officially recognized by the American Academy of Sleep Medicine and the American Sleep Association, Exploding Head Syndrome is a rare condition characterized by brief, intense auditory hallucinations. Usually, patients report hearing something like a cymbal crash, a gunshot, or an explosion as they fall asleep or wake up. Sometimes referred to as “exploding head disorder,” “exploding brain syndrome,” or “exploding syndrome,” there is still disagreement about how exploding head syndrome is diagnosed.
Nobody knows what causes Exploding Head Syndrome—some scientists think it could be caused by minor seizures in the brain’s temporal lobe, while others speculate it could be the result of stress or anxiety. Although startling, Exploding Head Syndrome is supposed to be painless. (There is little evidence of people experiencing Exploding Head Syndrome while awake.) There’s no standard treatment, although some patients have responded well to antidepressants. Interestingly, one researcher claimed recently to have found the earliest known written report of Exploding Head Syndrome. The French philosopher Rene Descartes once described a dream in which he heard a loud bang before seeing a bright flash of light as he awoke.
Perhaps the only thing stranger than your body rendering itself defenseless and immobile every night is wandering around while in that unconscious state. Formerly called “somnambulism,” sleepwalking is the most well-known parasomnia, with countless depictions in popular media (most recently in the movie “Sleepwalk with Me,” by comedian Mike Birbiglia).
According to the American Sleep Association, about 8.4 million people (3.6% of the U.S. population) are prone to sleepwalking. The condition is more common in children, who usually outgrow it by their teenage years. Similarly to Exploding Head Syndrome, it’s not clear what causes sleepwalking, and it’s not linked to any other conditions, but there are some risk factors. Those who suffer from depression, anxiety, or obsessive-compulsive disorder are more likely to sleepwalk. Sleepwalking usually occurs during deep sleep, right before the REM stage, when it’s harder to wake up.
There is no standard treatment for sleepwalking, and doctors usually recommend creating a safe environment to avoid injuries. Contrary to popular belief, it’s not dangerous to wake someone while they’re sleepwalking.
One of the most unsettling things about sleep is that our bodies are literally paralyzed during the REM stage. (Scientists think this might be a way to prevent us from acting out our dreams.) But what if you were conscious while your body was incapacitated? For some, that isn’t just a hypothetical question.
Sleep paralysis usually occurs just as someone drifts off to sleep or upon waking. For a brief moment, you are conscious but feel like you can’t move your limbs. On top of that, sleep paralysis is often accompanied by startling sensations and even visions, such as a shadowy figure looming in the corner of the room. Some scientists believe these visions could be the result of the brain’s heightened response to danger—“you can’t move, something must be wrong!”—while other research suggests visions correlate with stressful life events and belief in the paranormal. In general, doctors consider sleep paralysis to be a harmless (albeit scary and unpleasant) anomaly.
Catathrenia (sleep groaning)
Recognized only recently in medical literature, catathrenia is a rare condition characterized by groaning during sleep. The strangest thing is that catathrenia bears no clear relationship to either snoring (that involves inhaling, while groaning involves exhaling), sleep talking, or any more serious breathing problems. As with many parasomnias, scientists simply don’t know what causes catathrenia. The groaning can be loud or soft—some groans lasting as long as 30 seconds, accompanied by snorting or sighing—and they usually occur during REM sleep or deep sleep. The condition isn’t dangerous, although the patients may wake up with a sore throat. Catathrenia tends to affect men more than women, and is usually more bothersome to partners than to the patients themselves. If your partner is prone to catathrenia, doctors suggest wearing earplugs.