A young woman looks at her alarm clock while she lies in bed. Nearly one in five young people suffers from what’s called “exploding head syndrome,” a new study suggests.

People with the syndrome are startled awake from sleep by sudden loud noises—even the sensation of an explosion—that occur in their head, the researchers explained.

The syndrome tends to occur when a person is falling asleep. It may be caused by brain cells associated with hearing firing all at once, said study author Brian Sharpless, director of the psychology clinic at Washington State University.

“That’s why you get these crazy-loud noises that you can’t explain, and they’re not actual noises in your environment,” Sharpless said in a university news release.

Sharpless said conventional wisdom holds that exploding head syndrome is a rare condition that occurs primarily in people older than 50. But he had his doubts about that.

“I didn’t believe the clinical lore that it would only occur in people in their 50s. That didn’t make a lot of biological sense to me,” said Sharpless.

This new survey proved him right, he said.

Of 211 college students questioned, 18 percent said they had experienced exploding head syndrome at least once. Some said the problem had a significant impact on their lives.

More than one-third who experienced exploding head syndrome also experienced isolated sleep paralysis, a disorder in which a person can’t move or speak when waking up.

The study was published online recently in the Journal of Sleep Research.

Exploding head syndrome lasts just a few seconds but can be extremely frightening, leading people to think they’re having a seizure or a stroke, Sharpless noted. Some people are so rattled by the experience that they don’t even tell their spouse.

“They may think they’re going crazy and they don’t know that a good chunk of the population has had the exact same thing,” said Sharpless, who added there are no effective treatments for the syndrome.

However, just getting a diagnosis and learning they aren’t alone can help some people, he added.