Sleep Paralysis

I've blogged a few times recently about dreams/nightmares and what they mean, but sleep paralysis is something that affects us in our sleep that is quite different altogether. For anyone who has experienced sleep paralysis it can be quite unnerving, and having episodes of it myself in my later teenage years I certainly built up an interest in the subject. Wired.com describe a sleep paralysis episode like this:

'You wake up, but you can’t move a muscle. Lying in bed, you’re totally conscious, and you realize that strange things are happening. There’s a crushing weight on your chest that’s humanoid. And it’s evil. You've awakened into the dream world'

Penn State Live Official News Source has an excellent article on the subject, which the following paragraphs are taken from:

Less than 8% of the general population experience sleep paralysis, but it is more frequent in two groups - students and psychiatric patients - 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 muscle movement is inhibited, yet ocular and respiratory movements are intact" the researchers state in the current issue of Sleep Medicine 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% of students reported experiencing sleep paralysis, while nearly 32% of psychiatric patients reported experiencing at least one episode. People with panic disorder were even more likely to experience sleep paralysis, and almost 35% 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 hallucinations 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.

Wired Science documents another researcher in Sleep Paralysis, David McCarty from Louisiana State University Health Sciences Center’s Sleep Medicine Program. He says the good news is that sleep paralysis experience is pretty standard but rarely persists or causes serious life damage. 

“It’s very common, way more common than people realize, but usually it doesn't recur,” he said. “It’s not frequent enough to make people come in and ask the doctor for help.”