My first introduction to sleep paralysis was through Steven Yeun (aka Glenn on The Walking Dead). He described an incident where he was staying up late into the night, studying for a college exam:

“I went to sleep and while I was falling asleep I fell into sleep paralysis, and that would happen to me a lot,” he said in an interview with The Indoor Kids. “I started feeling a pushing on my chest, and I was like ‘what is this?’ So, I open my eyes … I looked at my stomach and there was a woman’s head.”

It would happen in moments when he was deprived of sleep and had a lot of anxiety, he said. Yeun had no scientific explanation for why his sleep paralysis would happen. However, researchers seem to think it’s closely tied to REM sleep.

The paralysis mechanism has a practical use. It’s in place so we don’t act out our dreams. However, there are cases where that paralysis function fails and we do things in our sleep we don’t remember.

Shelby Harris explains why we feel so terrified when we experience sleep paralysis.

On the flip side, Dan Denis, a Ph.D. student in psychology at the University of Sheffield, explains that sleep paralysis is a moment when “your mind wakes up, but your body doesn’t.”

As for why it happens, he cites one study where a team of Japanese researchers found they were able to induce sleep paralysis in some of their patients by depriving them of REM sleep. Other studies show that people who have irregular sleep, like college students who stay up late studying for exams and shift workers, are at an increased risk of experiencing sleep paralysis.

There’s no formal treatment for “curing” sleep paralysis. But knowing how weird our brains get when it doesn’t get enough sleep, the solution may just be improving diet and getting to bed on time.