Psychologists chase down sleep demons

Psychologists chase down sleep demons
This is The Nightmare. Credit: John Henry Fuseli

What do Moby Dick, the Salem witch trials and alien abductions all have in common? They all circle back to sleep paralysis.

Less than 8 percent of the general population experiences sleep paralysis, but it is more frequent in two groups -- students and -- according to a new study by psychologists at Penn State and the University of Pennsylvania.

Sleep paralysis is defined as "a discrete period of time during which voluntary is inhibited, yet ocular and respiratory movements are intact," the researchers state in the current issue of Reviews. Hallucinations may also be present in these transitions to or from sleep.

Alien abductions and incubi and succubi, as well as other demons that attack while people are asleep, are implicated as different cultural interpretations of sleep paralysis. The Salem witch trials are now thought possibly to involve the townspeople experiencing sleep paralysis. And in the 19th-century novel Moby Dick, the main character Ishmael experiences an episode of sleep paralysis in the form of a malevolent presence in the room.

Brian A. Sharpless, clinical assistant professor of psychology and assistant director of the psychological clinic at Penn State, noted that some people who experience these episodes may regularly try to avoid going to sleep because of the unpleasant sensations they experience. But other people enjoy the sensations they feel during sleep paralysis.

"I realized that there were no real sleep paralysis prevalence rates available that were based on large and diverse samples," Sharpless said. "So I combined data from my previous study with 34 other studies in order to determine how common it was in different groups."

He looked at a total of 35 published studies from the past 50 years to find lifetime sleep paralysis rates. These studies surveyed a total of 36,533 people. Overall he found that about one-fifth of these people experienced an episode at least once. Frequency of sleep paralysis ranged from once in a lifetime to every night.

When looking at specific groups, 28 percent of students reported experiencing sleep paralysis, while nearly 32 percent of psychiatric patients reported experiencing at least one episode. People with panic disorder were even more likely to experience sleep paralysis, and almost 35 percent of those surveyed reported experiencing these episodes. Sleep paralysis also appears to be more common in non-Caucasians.

"Sleep paralysis should be assessed more regularly and uniformly in order to determine its impact on individual functioning and better articulate its relation to other psychiatric and medical conditions," said Sharpless. He looked at a broad range of samples, and papers were included from many different countries.

People experience three basic types of during sleep paralysis -- the presence of an intruder, pressure on the chest sometimes accompanied by physical and/or sexual assault experiences and levitation or out-of-body experiences.
Up to this point there has been little research conducted on how to alleviate sleep paralysis or whether or not people experience episodes throughout their lives.

"I want to better understand how sleep paralysis affects people, as opposed to simply knowing that they experience it," said Sharpless. "I want to see how it impacts their lives."

Sharpless hopes to look at relationships between sleep paralysis and post-traumatic stress disorder in the future.

This research was supported in part by the National Institute of Mental Health.

Explore further

Out-of-body experiences may be caused by arousal system disturbances in brain

Citation: Psychologists chase down sleep demons (2011, October 17) retrieved 20 June 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Oct 19, 2011
this happened to me a couple of times, long ago. I had been practicing complete relaxation as a possible means of getting to sleep more easily. The technique involves first clenching muscles tightly so as to then let them relax completely, starting with the toes, feet, calves, thighs, etc, then doing the arms, working up to the head. Probably most people of heard of this.

So, effectively, I was teaching my body how to not move at all while lying supine. I think I just learned it too well; I habituated my brain and muscles to an extreme of relaxation, although it never seemed to help me actually get to sleep, if I recall correctly. But as is normal with dreams, this new [in]activity spontaneously occurred while I was dreaming. Probably an example of newly learned behaviour being consolidated during sleep but it backfired because made so immobile that normal shifting of the body during sleep just didn't happen.

Oct 19, 2011
... cont And I can vouch that it scared the crap out of me as I slowly became aware of being paralysed. Even after I opened my eyes I was stuck until a rush of adrenaline [I guess] woke me up enough for the motor cortex to muscles connections to be restored.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more