Sleep Paralysis Explained
What it is, why it happens, and what you can do about it.
Sleep paralysis is a short period, usually seconds to a couple of minutes, when you are awake or half awake but cannot move or speak. It is frightening, especially the first time, and it often comes with a sense of a presence in the room or pressure on the chest. It is also common and harmless in itself. This guide explains what is happening in the body, why it produces such vivid experiences, what raises the odds of an episode, and what seems to help.
What sleep paralysis is
During REM sleep, the stage in which most vivid dreaming happens, the brain switches off most of your voluntary muscles. This is called REM atonia, and it is protective: it stops you acting out your dreams. In sleep paralysis, the awareness comes back before the muscle switch-off has finished. You wake up, or partly wake up, while your body is still in the REM state, so you are conscious but cannot move.
It can happen as you fall asleep, which is called hypnagogic sleep paralysis, or as you wake up, which is called hypnopompic. The second kind is more often described in the accounts people share. Sleep researchers class it as a type of parasomnia, a group of unusual events linked to sleep, and not as a sign of a dangerous illness.
What it feels like
The core feature is being unable to move while you are aware of your surroundings. Many people also report one or more of these:
- A feeling of pressure on the chest or difficulty taking a full breath.
- A sense that someone or something is in the room, often threatening.
- Seeing, hearing or feeling things that are not there, such as footsteps, whispers, shadows or a figure by the bed.
- Strong fear, sometimes with a racing heart.
- A sensation of floating or being pulled, in some episodes.
These experiences are hallucinations produced by a brain that is partly in dream mode and partly awake. The threat-detecting parts of the brain are very active in REM sleep, which helps explain why the sense of danger is so common. The feeling that breathing is difficult is also explained: the breathing muscles that keep you alive keep working, but the chest can feel heavy because the other muscles are still switched off.
Why it happens: the common triggers
Researchers do not fully understand why it happens to some people on some nights, but several factors are linked to a higher chance of an episode:
- Sleep deprivation and an irregular schedule. Shift work, jet lag and late nights can all disrupt the normal passage into and out of REM sleep.
- Sleeping on your back. Many people report episodes more often in this position, though the reason is not settled.
- Stress and anxiety. Episodes are more common in periods of high stress.
- Other sleep problems. Sleep paralysis is more frequent in people with narcolepsy, and in people with sleep apnoea or other disrupted sleep.
- Family history. Some studies suggest it can run in families.
- Alcohol, and some medicines or substances. These can fragment sleep, and withdrawing from some of them can make REM sleep more intense.
| Question | Short answer |
|---|---|
| How long does it last? | Usually seconds to a couple of minutes |
| Is it dangerous? | Not in itself |
| How common is it? | About 8% of people in the general population, per a widely cited review, and more among students and people with anxiety |
| Who gets it? | Any age, though it often begins in the teens |
| What helps most? | Regular, sufficient sleep and lower stress |
Is sleep paralysis dangerous?
On its own, it is not. It cannot kill you, and your breathing continues throughout. The fear and the hallucinations are distressing but do not cause physical harm. What matters more is how often it happens and how it affects your sleep and your days. If you are having episodes often, are afraid to go to sleep because of them, or are very sleepy during the day, it is worth talking to a doctor. Frequent episodes can be a sign of another sleep problem such as narcolepsy, which can be treated.
What to do during an episode
Evidence for any single technique is limited, but these are widely suggested by sleep specialists and by people who experience it:
- Remind yourself that it is sleep paralysis, that it is temporary and that it is harmless. Knowing what is happening reduces the fear, which can shorten the episode.
- Focus on breathing slowly and calmly.
- Try to move something small, such as a finger, a toe or your eyes, instead of struggling with the whole body.
- Do not fight the hallucinations. Try to treat them as a dream that has spilled into waking.
How to make it less likely
- Keep a regular sleep schedule and aim for enough hours. This is the most consistent recommendation.
- If you notice episodes mostly when lying on your back, try sleeping on your side.
- Cut back on alcohol and heavy meals close to bedtime.
- Wind down before bed, and look for ways to manage stress, such as exercise or relaxation techniques.
- Keep a note of when episodes happen. A dream journal helps you spot patterns in timing, sleep position and stress.
Sleep paralysis in folklore and culture
People have reported this experience for centuries, and many cultures explained it as a supernatural visit. In English the old word mare, a spirit that sat on a sleeper's chest, gives us the word nightmare. Newfoundland tradition speaks of the Old Hag. In Brazil it is linked to the Pisadeira, a figure said to tread on the chests of those who sleep on a full stomach. In many places there are similar stories of a weight on the chest, a presence in the room and an inability to cry out. Our guide to Irish dream folklore looks at how dreams and the night were understood in Irish tradition, and the Samhain guide on Gods of Ireland covers the folklore creatures of the night that Irish tradition associates with that time of year.
Seen alongside the science, these stories describe the same pattern of symptoms: the paralysis, the chest pressure and the sense of a presence. It is a good example of how a real sleep event was explained in terms of the beliefs of the time. If you want to know what your own dream imagery might mean, you can look up individual symbols in the dream dictionary, though for sleep paralysis itself the useful information is practical.
Sleep paralysis and dreams
Sleep paralysis is not itself a dream, but it borrows the imagery of one. Because the hallucinations come from the REM system, they often feel like a nightmare that you are awake for. People sometimes confuse it with night terrors, which happen in deep sleep, and with a false awakening, in which you dream that you have woken up. Sleep paralysis can also be the doorway to a lucid dream for people who practise it, which is covered in our lucid dreaming guide, but it is not something to chase if the experience frightens you.
Want to know what a specific symbol in your own dream means?
Try the free AI Dream Analyzer →Frequently Asked Questions
What causes sleep paralysis?
It happens when you become aware during REM sleep, while the brain is still keeping your muscles switched off. It is more likely with poor or irregular sleep, stress, sleeping on your back and some other sleep disorders.
Can sleep paralysis kill you?
No. Sleep paralysis cannot kill you. Your breathing and heartbeat continue normally, and the episode passes on its own, usually within seconds or a couple of minutes.
How long does sleep paralysis last?
Most episodes last from a few seconds to a couple of minutes, though they can feel much longer because of the fear.
Is sleep paralysis a demon or a spirit?
No. The sense of a presence is a hallucination produced by the brain in a half-awake REM state. Many cultures explained it in terms of spirits, but there is a well-understood physical cause.
How do I stop sleep paralysis?
Regular, sufficient sleep and lower stress are the most reliable steps. During an episode, staying calm and trying to move a finger or toe can help. If episodes are frequent or you are sleepy in the day, see a doctor.