What is sleep paralysis?

Sleep paralysis consists of a period of inability to perform voluntary movements either at sleep onset (called hypnogogic or predormital form) or upon awakening (called hypnopompic or postdormtal form).

Sleep paralysis may also be referred to as isolated sleep paralysis, familial sleep paralysis, hynogogic or hypnopompic paralysis, predormital or postdormital paralysis

What are the symptoms?


A complaint of inability to move the trunk or limbs at sleep onset or upon awakening
Presence of brief episodes of partial or complete skeletal muscle paralysis
Episodes can be associated with hypnagogic hallucinations or dream-like mentation (act or use of the brain)


Polysomnography (a sleep recording) shows at least one of the following:


suppression of skeletal muscle tone
a sleep onset REM period
dissociated REM sleep


Is it harmful?

Sleep paralysis is most often associated with narcolepsy, a neurological condition in which the person has uncontrollable naps. However, there are many people who experience sleep paralysis without having signs of narcolepsy. Sometimes it runs in families. There is no known explanation why some people experience this paralysis. It is not harmful, although most people report feeling very afraid because they do not know what is happening, and within minutes they gradually or abruptly are able to move again; the episode is often terminated by a sound or a touch on the body.

In some cases, when hypnogogic hallucinations are present, people feel that someone is in the room with them, some experience the feeling that someone or something is sitting on their chest and they feel impending death and suffocation. That has been called the “Hag Phenomena” and has been happening to people over the centuries. These things cause people much anxiety and terror, but there is no physical harm.