MYSTERIES · GHOSTS AND MYSTERIES

Zmora, or sleep paralysis: when something sits on your chest

In folk tales, it was the zmora that would sit upon the chest of a sleeping person in the night. Today we know it is sleep paralysis, but the experience is no less terrifying for that.

Ezostylia Editorial Team · facts checked in sources · updated 31.10.2026

What it looks like

A person wakes up or is falling asleep and suddenly discovers that they cannot move or cry out. They often feel a pressure on their chest, a presence in the room, see a figure by the bed, or hear footsteps. An episode usually lasts from a few seconds to a few minutes and passes on its own.

What happens in the brain

During the REM phase of sleep, the brain switches off muscle tone so that we do not act out our dreams. During sleep paralysis, consciousness has already woken up whilst the muscles are still "switched off," and dream imagery overlays the real room. Hence the realistic hallucinations.

How often it occurs

According to a review of 35 studies (Sharpless and Barber, 2011), approximately 7.6% of the general population, 28.3% of students, and 31.9% of psychiatric patients have experienced at least one episode of sleep paralysis in their lifetime. It is encouraged by sleep deprivation, irregular hours, stress, and sleeping on one's back.

Zmora and her sisters

The Slavic zmora, mara, or gniotek is a creature that strangles sleeping people in the night. Similar figures are known the world over: the Nordic mara (hence the English word nightmare), the old hag in Newfoundland, kanashibari in Japan. Johann Heinrich Füssli's famous painting "The Nightmare" from 1781 depicts a demon sitting on the chest of a sleeping woman.

What helps

regular sleep times and a sufficiently long sleep,
sleeping on one's side rather than on one's back,
less alcohol and fewer screens before bed,
during an episode: calm breathing and attempting to move a finger or the tongue,
when episodes are frequent or sudden daytime sleepiness appears, it is worth speaking to a doctor, as they can sometimes be a symptom of narcolepsy.

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Sources

A clinician's guide to recurrent isolated sleep paralysis (Dove Press) · Sleep paralysis, Wikipedia

FAQ

Frequently asked questions

Is sleep paralysis dangerous?

In itself, no, though it can be very frightening. Frequent episodes, particularly when accompanied by daytime sleepiness, are worth consulting a doctor about.

How often do people experience sleep paralysis?

According to the review by Sharpless and Barber (2011), approximately 7.6% of the general population, 28.3% of students, and 31.9% of psychiatric patients have experienced it at least once.