Why people with sleep paralysis have supernatural visions

Shadowy figures lurking in the dark, alien visits, out-of-body experiences, even feelings of suffocation—this is just some of what people with sleep paralysis endure. And according to first-hand accounts in the new documentary The Nightmare, the horror feels as real as day.

The film, which premiered at Sundance earlier this year and just hit select theaters, features interviews with eight people suffering from the condition, as well as actor reenactments of their terrifying experiences in bed. After watching the film, my first thought was: Either this depiction of sleep paralysis is extremely exaggerated, or these people are insane.

But are they? The filmmakers didn’t interview medical professionals, nor did they touch on the science behind sleep paralysis. And so, intrigued, I set out to fact check the movie’s depictions of the condition to find out what, exactly, happens in the brains and bodies of up to 40 percent of the population who experience sleep paralysis.

“I have not met a patient who was not anxious or did not feel a lot of anxiety due to sleep paralysis,” Alon Avidan, director of the UCLA Sleep Center, told me. “It’s very real for them, and it’s hard for them to interpret what’s happening around them.”

What happens in the brain during sleep paralysis?

For the uninitiated, sleep paralysis is a condition in which a person feels conscious but paralyzed, except for the ability to move his or her eyes and breathe, immediately after waking up. The sufferer feels trapped and often starts to panic, said Jan Dirk Blom, an assistant professor of psychiatry at University of Groningen in the Netherlands who has studied sleep paralysis extensively.

Sleep paralysis happens when a person experiences an incomplete transition from sleep to wakefulness, and the related processes in the brain that usually snap on simultaneously simply fail to do so, said Blom. Instead, these processes become desynchronized (or “disassociated”).

Want to see really, really sleep deprived people do comedy? Watch Tuesday’s live taping of The Chris Gethard Show featuring special guest Seth Meyers.

“Normally, during Rapid Eye Movement (or REM) sleep, our consciousness is in the ‘off’ position and our ability to move our muscles is also in the ‘off’ position,” said Blom, who also heads up the Outpatient Clinic for Uncommon Psychiatric Syndromes at the Parnassia Psychiatric Institute. “Sleep paralysis means that our [muscles] remain in the ‘off’ position while our consciousness switches to an ‘on’ position.”


According to UCLA’s Avian, our bodies naturally slip into a frozen state when we sleep in order to keep us safe from ourselves, “like a protective mechanism to keep us from acting our dreams.”

Which is why when the processes become disassociated, the brain and body become confused. Avidan said a given episode of sleep paralysis can last anywhere from a few seconds to a few minutes, causing an extreme amount of anxiety and fear for a patient who experiences it.

But if sleep paralysis is simply an in-between physical state, why do patients report “supernatural” occurrences such as seeing and feeling the presence of an intruder or aliens, or even having out of body experiences? As one woman in the film says, she once felt a demonic creature climb on her bed, get on top of her, and rape her. At least she felt like she was being raped.

Where do ‘shadow people’ come from?

The vivid sensory experiences people sometimes experience during sleep paralysis are called “hypnagogic” and “hypnopompic” hallucinations—they occur when one is falling asleep and waking up, respectively. “They may involve hearing footsteps, experiencing levitation and autoscopy, and seeing, hearing, and sensing the presence of menacing intruders in one’s bedroom,” wrote Baland Jalal, a researcher at UCSD’s Center for Brain and Cognition, in one of his many papers on sleep paralysis.

While many people believe these hallucinations are real-life supernatural or demonic creatures lurking in their bedrooms, scientists agree the visions are all in their brains—but that doesn’t mean they don’t feel real. Some people even report feeling like a person is strangling them or sitting on their chest, leaving them gasping for air.

Blom said that patients see these shadowy figures—often referred to as “the intruder” or “shadow people”—and other beings because their threat-detection systems in the amygdala are activated. After feeling trapped in their own bodies, patients instantly become hypervigilant about their surroundings.

“Our brains are wired in such a way that we are bound to over-detect predators and other types of danger. This has an evolutionary advantage, because it is safer to spot a tiger now and then when it is not around than to miss one when it is,” Blom said. But “this evolutionary advantage turns into a disadvantage when the brain attempts to make sense of its surroundings while it experiences a threat that in reality does not stem from the outside world, but from its own reaction to sleep paralysis.”

We fear what we know

As many people who suffer from sleep paralysis explained in The Nightmare, the hallucinations are never friendly. But why do the intruders feel so profoundly scary?

Because they stem from what’s already in our heads, Blom said. Which is why “individuals with a Christian background may feel that they are visited by a demon, those with a Muslim background by a djinn, and victims of sexual abuse are visited by a sex offender.”


Jalal from UCSD echoes this sentiment, adding a more neurological explanation. In his research he hypothesizes that out-of-body experiences and the form the figures take can be linked a functional disturbance of the brain’s temporoparietal junction and the right parietal cortex—regions that help distinguish between the “self” and “other” and construct a neural understanding of our own body.

During REM sleep the temporoparietal junction is turned off—and so, during sleep paralysis, the brain gets confused and can’t figure out how to build a sense of self, resulting in “all kinds of bizarre bodily hallucinations, such as out-of-body experiences, seeing one’s limbs or entire body rotate in the air like a tornado or sink deep into the bed as if drowning in quicksand,” said Jalal.

“The mind literally casts a shadow, just like the body does,” he said. “As the barrier between self and other dissolves, the person mistakes his own ‘shadow’ (or body template) for a separate entity.” Jalal compares the experience to amputees who feel phantom limbs. In reality, the amputee is feeling the presence of their arm on their internal body template.

However, the human forms “seen” during sleep paralysis aren’t identical replicas of one’s self—they can take on terrifying attributes thanks to these disturbances in the brain. “When REM dreaming becomes activated as well, the shadowy-figure can take on all kinds of sophisticated shapes and dimensions, and the entire plot thickens,” said Jalal. “At this point, memory and the narrative abilities of other brain regions play a role in the evolving hallucination.”

How to exorcise the demons

Research suggests that sleep paralysis affects 18 to 40 percent of the population. Sometimes it happens once in someone’s life, sometimes it’s recurring, and very rarely it’s a symptom of an underlying condition like narcolepsy.

UCLA’s Avidan said more often than not, the top cause of sleep paralysis is sleep deprivation. He says most of his patients are “generally healthy college students who are studying for finals, getting three or four hours of sleep. Adding, “They’re very stressed, and they’re drinking a lot of caffeine.”

To combat sleep paralysis, Avidan said the best thing to do is to get on a regular sleep schedule, sleep at least seven to eight hours a night, and cut out stimulants. If all that fails and narcolepsy is ruled out, a doctor can prescribe medication to manage the condition; it’s usually an antidepressant, which simply reduces Rapid Eye Movement (REM) sleep, said Avidan.

Of course, some people learn to live with sleep paralysis and block out the nightmares. “I have met a few people who are so familiar with sleep paralysis that they don’t care anymore,” said Blom. “But most people react with a fear that they describe as ‘off the scale.'”