

You may be unable to move your arms or legs, body and head. You can breathe and think, but you may be unable to speak.

The paralysis may last for only seconds or a few minutes. Then it disappears and you are able to move again.

This describes a typical episode of sleep paralysis. It is a common sleep disorder that is classified as a “parasomnia.” Episodes can cause you to feel intense anxiety.

Sleep paralysis occurs when the line between sleep and wakefulness is blurred. Normally your brain paralyzes many of your muscles during the stage of rapid eye movement sleep – or REM sleep. This paralysis is called “atonia.”

You may experience sleep paralysis if atonia lingers as you wake up from REM sleep; it also may occur if you transition quickly from wakefulness into REM sleep.

Sleep paralysis may occur together with hallucinations. You may imagine that you see or hear something; you even may think that someone else or something is in the room with you.

Across cultures the strange sensation of sleep paralysis has evoked some vivid descriptions. In 1664 a Dutch physician published a case history of a woman with sleep paralysis. “’The devil lay upon her and held her down,” he wrote.

In Japan sleep paralysis is called “kanashibari.” The term is rooted in Buddhism; long ago it was believed that Buddhist monks could use magic to paralyze others.

In Newfoundland sleep paralysis has been called an attack of “Old Hag.” In China it has been labeled “ghost oppression.” A new study reports that in Mexico people may say that sleep paralysis feels like “a dead body climbed on top of me.”

Sleep deprivation may trigger an episode of sleep paralysis. Other related factors may include stress and sleep related leg cramps.

Sleep paralysis tends to be only a mild problem; there are no medical complications. But it also can be one symptom of narcolepsy.

Learn more about parasomnias.