Just as she fell asleep, Rachel awoke to a resounding crash. “It sounded as though a painting had fallen off the wall,” she recalls, “and taken down every ornament on the mantelpiece with it.”
She leapt out of bed, terrified that an intruder had broken into her apartment. It was around 2 a.m. in the sweltering Australian summer and blackouts were rolling through Melbourne — a cruelly ironic consequence of air conditioner use across the city. Her phone was dead, she couldn’t charge it, and she had no light besides a battery-powered, kewpie doll-shaped nightlight. She was also, by the by, living alone for the first time in her life, having recently come out of a relationship. Not the most sleep-friendly circumstances, heatwave and hypothetical burglar aside.
Armed with her kewpie doll, Rachel moved cautiously from room to room, searching for the source of the noise. She found nothing. No one was lurking in the closet, every painting was in place, the mantel undamaged. So she went back to bed, comforted — to the extent one can be comforted — that it was all in her head.
“Needless to say,” she says, “my sleep was troubled for the rest of the night.”
Nights like this are a regular occurrence for Rachel, who suffers from a mysterious sleep disorder known as Exploding Head Syndrome (EHS) Let’s get the obvious question out of the way: despite what its death-metal band name might lead you to believe, EHS is physically harmless. It doesn’t make your head explode, it’s not associated with any pain and there aren’t even any known physical symptoms. The emotional toll, however, can be severe, with sufferers constantly jolted from sleep with the unknown sound and the suspicion that something is wrong.
What is the glitch that causes the disorder? The truth is there’s not much we know about EHS other than the broad strokes: It’s a hypnagogic hallucination that causes patients to hear a loud noise — often described as gunfire, cymbals crashing or an explosion — as they transition from wakefulness to sleep.
Like many sleep disorders, EHS is little documented and ill-understood. The largest study of the condition, published last year in the Journal of Sleep Research, profiled only 211 undergrads, a mere 20 percent of whom reported EHS experiences. The causes remain elusive, and there’s even disagreement as to whether it’s a sleep disorder at all.
“The jury is still out as to whether EHS is caused by a neuronal dysfunction or a hearing issue,” says Dr. Daniel Kantor, professor and former president of the Florida Society of Neurology. That first term refers to a problem with the nerves that govern hearing, which might activate when they should be shutting down for sleep, causing a false sensation of sound. As Dr. Kantor also suggests, EHS may alternately be caused by problems in the inner ear, seizures or bleeding in the brain; there simply isn’t enough research to say for sure.
The Sleep Research study found that EHS may be associated with sleep paralysis, which is at least true in Rachel’s case. She’s suffered from sleep paralysis since she was thirteen — she’s 29 now — and from EHS since she was ten. “I always hear one of three sounds,” she says. “My bedroom door slamming loudly, my guitar being strummed violently on an open chord, or — most troublingly — my own name being shouted.”
As is the case with sleep paralysis, simple awareness that EHS is a hallucination might be the closest we have to a cure. “EHS may be frightening to those affected, but it is not dangerous,” says Dr. Kantor. “This reassurance can be helpful for some individuals.” He notes that certain medications, including antidepressants, have been tested “to mixed success,” but never in the setting of a large clinical trial. He also cautions patients to ensure their hallucinations are not symptoms of other, more insidious conditions.
For the vast majority of EHS victims, though, the “it’s just a dream” solution is a half-measure at best. When Rachel felt her way around her shadowy apartment hunting for an intruder, she knew perfectly well it was probably in her head. But what reasonable person would risk the off chance it’s not?
The effects of stress and lost sleep are far from harmless, and they accrue with every night of troubled slumber.
“I don’t enjoy sleeping,” says Rachel, pointing to her unfortunate combination of sleep paralysis and EHS. “I only sleep a few hours a night, usually broken. Currently I’m getting by on four hours, on average, per night.”
Hers may be an unusual case when it comes to EHS. Or it may not. Until the science catches up, we can only hope other patients are luckier than she.