Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea; they are not medical tools.
Tap the buttons and slide the sliders.
Tap the sleeper. Which part is asleep in the in-between moment?
Step through REM sleep, sleep paralysis and full wakefulness: what differs between them?
Tap the sleeper. Can they move yet?
Drag along the night. When does REM sleep come, and when does it get longer?
Scrub the hypnogram: where do the REM periods fall, and how do they change toward morning?
Slide through the night. When do dreams come?
A typical pattern, simplified. Real nights vary from person to person.
Turn the switch off. What would the dreamer's body do?
Disable atonia in this toy model: this is why REM muscle paralysis exists.
Turn the switch off. What happens?
A made-up demo: without the switch, dream movements can get through, but this animation isn’t how a real sleeper would move.
Turn the dial from asleep to awake. Where is the brain awake but the muscles still off?
Turn the dial: sleep paralysis is the window where wakefulness has returned but atonia hasn’t ended.
Turn the dial. Where is the brain awake but the body still asleep?
The dial is a simple picture of the idea, not a measurement.
Switch each habit. Which make sleep paralysis more likely?
Toggle the well-established risk factors and watch the illustrative meter.
The meter is a rough guide with made-up numbers, not real odds.
Tick off each step. What can you do if it happens?
Tick off what helps during an episode, what prevents it, and when to see a doctor.
Tap each step to make your calm plan.
Sometimes a person wakes up in the night and can't move for a little while. They can see and breathe, but their arms and legs won't move yet. This is called sleep paralysis. It can feel strange, but it does not hurt you, and it goes away by itself.
When you sleep, your brain goes from light sleep to deep sleep, and then to dream sleep. This happens again and again all night.
In dream sleep (called REM sleep) you might dream you run or kick a ball. So during REM sleep your brain flips a switch that makes your arms and legs floppy and still. That way you stay safe in bed. You keep breathing the whole time.
Sometimes you wake up before the switch turns off. Your brain is awake, but your body is still asleep. Some people see or hear bits of a dream for a moment. They are not real, and they fade away.
Remember it will stop on its own. Take slow breaths and wiggle one finger or toe. Go to bed at the same time every night and get lots of sleep.
This page explains how sleep works; it isn't medical advice. If it happens a lot or worries you, talk to a parent or doctor.
Sleep paralysis is when you wake up (or are just falling asleep) and, for a short while, you can't move or speak, even though you're aware of your surroundings.13 It's caused by a timing mix-up between two parts of sleep. During REM sleep, the dreaming stage, your brain switches off most of your arm and leg muscles so you don't act out your dreams. Sleep paralysis happens when your mind wakes up while that "muscle switch" is still on.34
It usually lasts from a few seconds to a couple of minutes, then passes on its own.2 You keep breathing normally and your eyes can still move.23 It can feel frightening, but on its own it isn't a serious medical risk.3
Sleep isn't one long switch-off. It's made of two basic types, non-REM sleep (which has three stages, from light to deep) and REM sleep, and you cycle through them several times a night.6 The first REM period usually comes about 90 minutes after you fall asleep.6 A typical night has four to six cycles, and the REM parts get longer toward morning.67
| Stage | What your brain does | What your muscles do |
|---|---|---|
| Light sleep (stages 1–2) | Slows down; easy to wake | Relaxed, can still move |
| Deep sleep (stage 3) | Slowest; very hard to wake | Very relaxed, can still move |
| REM sleep | Almost as busy as when awake; vivid dreams | Arms and legs switched off ("REM atonia"); eyes and breathing keep going |
| Sleep paralysis | Awake and aware | Still switched off, for a short while |
The chart in chapter 2 of the explainer is a simplified, typical pattern, not a recording of one real person's night. Real nights vary a lot.
In a dream you might run, jump or kick a ball. If your body copied every move, you could fall out of bed or get hurt. So during REM sleep, your brain stem (especially parts called the pons and medulla, at the base of the brain) sends signals that relax the muscles you use for posture and for moving your arms and legs.6 Doctors call this REM atonia ("atonia" means "no muscle tone").3
Normally, the switch turns off as REM ends, and you never notice it. In sleep paralysis, researchers think you end up in a mixed state: partly awake and partly still in REM sleep. You're aware of your room, but the REM muscle switch hasn't let go yet.48 It can happen while falling asleep or while waking up.3
The "brain awake, body asleep" dial in chapter 4 is a picture of this idea, not a measurement: the points where the rings change are made up for clarity.
Nobody knows the whole answer yet, and anyone can have it.24 But researchers and sleep doctors have found things that make it more likely:134
It's also linked with some conditions, such as insomnia, anxiety and a sleep condition called narcolepsy.14 It usually first shows up in the teenage years (on average around ages 14 to 17) and is most common in people's 20s and 30s.3
The meter in chapter 5 uses made-up weights to show which way each habit pushes. It isn't a real risk calculator.
More common than most people think, though estimates vary a lot, from about 5% to 40% of people.3 A large review by Sharpless and Barber combined 35 studies with 36,533 people. It found that about 7.6% of the general population, 28.3% of students and 31.9% of psychiatric patients had had at least one episode in their lives.5 Cleveland Clinic estimates around 30% of people worldwide have at least one episode.2
You're awake and can see your room, but you can't move your arms, legs or head, and you can't speak.3 Many people feel anxious or scared, which is understandable.2 Some people also see, hear or feel things that aren't really there.3 These are called hallucinations, and the leading explanation is simple: because you're still partly in REM sleep, the images and feelings of dreaming carry over into waking for a moment.48 They fade as you wake up fully. Long before scientists knew about REM sleep, people in many places made up stories to explain the experience.8
No. Sleep doctors describe it as harmless on its own: it isn't a serious medical risk and it ends by itself.23 Your breathing muscles keep working the whole time.3 The main problem for some people is worry: if episodes happen often, they can make you anxious about going to bed, which can cut into your sleep.4
An episode can also end when someone touches you or talks to you, and it's safe for someone to gently wake you.23
Because sleep paralysis is linked to short and irregular sleep, good sleep habits are the main way to make it less likely:13
Want to know more about why sleep matters so much? See why sleep is important, and for what's happening in the dreaming brain, how dreams work. Tired the next day? That's when yawning kicks in.
You don't usually need medical help for sleep paralysis.1 But talk to a parent and a doctor if it happens often, if it makes you anxious or scared to go to sleep, or if you feel very tired during the day.13 Frequent sleep paralysis together with strong daytime sleepiness can be a sign of narcolepsy, which a sleep doctor can check and treat.3 For most people, no tests are needed, and help focuses on better sleep and on any worry or stress.3
No. Doctors describe sleep paralysis as harmless on its own. It can feel frightening, but your breathing muscles keep working and it ends by itself, usually within seconds to a couple of minutes. If it happens often or makes you scared to go to sleep, talk to a doctor.
Usually not. Many episodes are 'isolated', meaning they happen on their own in otherwise healthy people, often after poor or irregular sleep. Frequent episodes together with strong daytime sleepiness can be a sign of a sleep condition such as narcolepsy, which a doctor can check.
Remind yourself it's temporary and harmless, breathe slowly, and focus on a small movement like wiggling one finger or toe. Episodes also end on their own, or when someone touches or talks to you.
The same REM 'muscle switch' that keeps your arms and legs still while you dream is thought to also keep the muscles you'd use to speak or shout relaxed, which is why many people find they can't call out. Your breathing muscles and eyes keep working.
Most episodes last from a few seconds to a couple of minutes. Rarely, people report longer ones.
Estimates vary a lot, from about 5% to 40% of people. A large review of 35 studies found about 8% of the general population and 28% of students had had at least one episode. It often starts in the teenage years.
Because you're partly still in REM sleep, the dreaming state. Dream-like images, sounds or feelings can carry over into waking for a moment. They aren't real and they fade as you fully wake up.