What Is Sleep Paralysis (and Why Is It So Terrifying)?

You’re finally ready for bed, so you turn out the light and prepare for some much-needed shut-eye. For once, you drift off with no problem…but then, something extremely weird happens. You’re aware of everything that’s going on in your bedroom, but you can’t move your body. At all. This terrifying symptom is called sleep paralysis, and it’s actually pretty common. It affects up to 50 percent of us at one point or another. So what is sleep paralysis? Here’s what causes it (and what to do if it’s freaking you out).

Get ready for some sci-fi-level stuff: Sleep paralysis happens when your body slips between sleep and consciousness. You’re aware of everything that’s happening around you, but you can’t move or speak. It typically occurs while waking up or falling asleep, and lasts only a few minutes. In some extra-creepy cases, sleep paralysis can be accompanied by visual or auditory hallucinations. (Eek.) Basically, you’re still dreaming, but you feel like you’re wide awake.

It’s pretty common and can happen to anyone, but you might be more likely to experience it frequently if you have narcolepsy or other sleep disturbances. Sleep deprivation, substance abuse or recent changes in your sleep cycle may also play a part. Our friends at WebMD tell us that the cause of sleep paralysis is typically REM dysfunction—for example, if your body is still in REM sleep, but you suddenly wake up before your body has finished the cycle, you might feel “awake” while your body is still asleep.

Sleep paralysis is harmless but can be pretty damn scary while it’s happening (some experts believe that people who have reported alien abductions may have actually just experienced sleep paralysis—sorry, Cousin Sally). For most people, the experience is occasional and requires no treatment. But if sleep paralysis becomes a recurring issue, talk to a doctor to determine if medications or an underlying condition could be the cause.