Sleep paralysis

How it works

During REM sleep, the stage where most dreaming happens, the brainstem switches off the muscles of the body. This stops you from acting out your dreams⁴. In sleep paralysis, your mind wakes up before that switch is turned back on¹. You are aware. You can breathe and move your eyes. You cannot move your limbs or speak.

An episode lasts seconds to a few minutes. It ends on its own, or when someone touches you or speaks to you¹. Because the brain is still partly in REM, dream content leaks into the room. Common experiences are a sense of a presence, pressure on the chest, a shadowy figure, footsteps, or a buzzing sound¹. The chest pressure comes from the shallow, fast breathing of REM sleep, which feels wrong when you are awake to notice it.

About 7.6% of the general population report at least one episode in systematic reviews¹. Among students the figure is about 28%¹. A 2024 meta-analysis put the lifetime figure near 30%¹. It is more common in younger people, in people who sleep on their back, and after lost sleep, jet lag, or stress¹.

Is it a problem?

No. It is not a stroke, not a seizure, and not possession. Breathing continues normally the whole time. It does not damage the brain. Episodes become rarer with a regular sleep schedule, enough sleep, and sleeping on your side¹. During an episode, focus on moving one finger or toe. Small movements often break it.

See a doctor if episodes happen several times a week, or if you also fall asleep suddenly during the day or go weak when you laugh. That combination can be narcolepsy, which is treatable¹.

History and culture

Nearly every culture has a name for this. In Newfoundland it is the Old Hag, who sits on the sleeper’s chest². In Japan it is kanashibari, “bound in metal”³. Medieval Europe blamed a demon called the incubus. The painting “The Nightmare” by Henry Fuseli, from 1781, shows a creature crouched on a sleeping woman¹. Some researchers think modern reports of alien abduction describe the same experience¹.