Aaron Mahnke

Just the thought of it would make anyone want to scream.

But that's where things actually become even more terrifying.

Despite opening your mouth and willing yourself to scream, not a single sound escapes your lips.

No matter what you do or how hard you try, you've lost control over your entire body.

You're frozen, one might even say paralyzed.

If you've never experienced anything like this, consider yourself lucky.

For a significant portion of the population, though, this isn't just a thought exercise.

It's reality.

Scientists say about 8% of the general population experiences sleep paralysis on a somewhat regular basis.

Beyond that, multiple studies say that somewhere between 20 and 45% of us have undergone sleep paralysis at least once in our lives.

Over the years, many people have tried to explain how the phenomenon works.

A second-century dream interpreter named Artemidorus of Daldus believed that sleep paralysis was simply the god Pan having intimate relations with the dreamer, which, according to him, was a sign of good fortune.

And the acclaimed medical practitioner Galen, considered by most to be the father of medicine, blamed sleep paralysis on gastric upset, while one 10th century Persian scholar said that it was caused by, as he put it, vapors of phlegm traveling from the stomach to the brain.

In reality, hallucinations during sleep paralysis are not caused by vapors of any kind.

If your consciousness wakes before your body does, then your mind, for lack of a better term, freaks out.

The emotional center of your brain shifts into panic mode, which can sometimes make people see or hear things that aren't actually there.

Like, for example, demons perched on top of their paralyzed bodies.

Back in the day, though, they didn't yet have the tools to understand that neurological process.

So it may be unsurprising that for thousands of years, those outside the medical profession, and even some within it, believed that sleep paralysis was brought on by some kind of demonic entity.

The ancient Babylonians believe that it was caused by the female demon Lilith.