The science of sleep paralysis, a brain-body glitch making people see demons and witches

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Many people who experience sleep paralysis see frightening hallucinations some call "sleep paralysis demons." Illustration by Leah Abucayan/Alberto Mier/CNN via CNN Newsource
Baland Jalal lay in bed terrified, experiencing his own real-life horror film.
Newly awake, the 19-year-old could see his surroundings but couldn't move or speak, and he didn't know why.
He thought, ''My God, what do I do?'' Jalal, now 39, said of that moment in 2005. 'I tried to call my mom (and) dad, but no words would emerge from my throat. … I had this ominous presence of a monster, and it lifted my legs up and down.
'It strangled me, trying to kill me. And I was 100% sure that I was going to die,' Jalal added. 'It literally feels like all the evil of the universe is condensed into a bubble, and it's in your bedroom.'
This type of hallucination is a hallmark for many people with sleep paralysis.
It occurs during transitions into or out of rapid eye movement, or REM, sleep, similar to a traffic jam at a busy intersection — your brain, awake and alert, and body, still asleep and immobilized, collide momentarily, said Dr. Matthew P. Walker, director of the Center for Human Sleep Science at the University of California, Berkeley, via email.
Following deep sleep, REM sleep is the next critical phase of sleep cycles, characterized by more dreaming that's also extra vivid and lifelike, and by faster heart rate and breathing. It's essential for memory, concentration, mood regulation and immune function.
Jalal's experiences propelled him to study this phenomenon around the world. He aimed to discover the cause of sleep paralysis, he said, and why some people with the diagnosis 'have these powerful encounters where it feels like evil of epic proportions.'
He has since earned a doctorate in psychiatry and is now a researcher in Harvard University's psychology department and a leading expert on sleep paralysis. He also treats patients struggling with it.
An estimated 30% of people worldwide experience at least one episode of sleep paralysis in their lifetime, according to the Cleveland Clinic. How many of those people have recurring and impairing sleep paralysis isn't clear, but the percentage is likely low, Jalal said.
Here's what else you should know about sleep paralysis and how it can be managed.
The science and symptoms of sleep paralysis
In REM sleep, our bodies are paralyzed so we don't act out our dreams and risk hurting ourselves or others, Jalal said. Sleep paralysis episodes are usually only a few minutes long but can last up to 20 minutes, according to the Cleveland Clinic.
During sleep paralysis, however, 'we regain consciousness before the muscles regain their freedom from REM-induced paralysis,' said Walker, who is also a professor of neuroscience and psychology at the University of California, Berkeley
About 40% of people with sleep paralysis have visual, auditory or tactile hallucinations, such as pressure on one's chest or feeling out of body, Jalal said. For about 90% of those individuals, the illusions are terrifying. They can include ghosts or cat- or alien-like creatures, and their actions can be as innocuous as simply approaching them or as nefarious as molesting or trying to kill them.
In Jalal's academic travels, he discovered the contents and interpretations of hallucinations, views on what causes sleep paralysis, and episode frequency and duration can all also have a cultural basis. People living in Egypt and Italy, for example, would often see witches and evil genies, hold them responsible and think they could die from sleep paralysis, Jalal said. People in Denmark, Poland and parts of the United States, on the other hand, have less supernatural or exotic explanations and less fear.
'Why do we see these monsters? Is it the dreaming imagery … that's spilling over into conscious awareness?' Jalal said. 'My answer to that is, according to my research, no, not exactly. But it's part of it.'
When you're aware yet paralyzed and confused, your natural reaction is to escape that situation. Your brain is bombarding your body with signals to move, but your body can't return any feedback.
Jalal's theory, in short, is that your brain says, 'to hell with it' and concocts a story it thinks your body must be facing to be experiencing such bizarre symptoms.
The reduced activity in your prefrontal cortex — responsible for reason and logic — also contributes to hallucinations becoming 'extremely realistic and emotionally charged, amplified by an overly active amygdala, the brain's emotional alarm center,' Walker said.
Causes and risk factors of sleep paralysis
Though scientists know that wake-sleep glitch is what's happening during a sleep paralysis episode, they're not entirely sure why. But there are several factors that can increase the risk of fragmented sleep and sleep paralysis.
Those factors include stress and related conditions such as anxiety, post-traumatic stress disorder (PTSD), bipolar disorder and panic disorder, experts said. Much of Jalal's sleep paralysis occurred when he was in school. Now when he has an episode once or twice per year, it's usually during a high-stress period, he said. (Once you've experienced sleep paralysis, you can be conscious of that during an episode but still feel afraid.)
Other common contributors are sleep deprivation, jet lag, an irregular sleep schedule, sleep disorders such as narcolepsy, and genetic factors, Walker and Jalal said.
Obstructive sleep apnea, substance use disorder and some medications — such as those for attention deficit hyperactivity disorder — can also raise risk, according to the Cleveland Clinic.
Is sleep paralysis dangerous?
As scary as sleep paralysis may sound, it's not actually dangerous, experts said. But depending on how recurring it is, sleep paralysis can be a sign of an underlying sleep disorder, Jalal said.
Regular episodes can also lead to anxiety around sleep and then avoidance of sleep, Jalal said. This pattern can interfere with your daily energy and ability to function. And if you often have frightening hallucinations, that can lead to anxiety or trauma-like symptoms.
How is sleep paralysis treated?
Sleep paralysis can be significantly alleviated with several practices or treatments, Walker said — starting with healthy sleep habits, for one. That includes seven to nine hours of restful sleep nightly.
Maintaining a sleep schedule consistent in quality and quantity 'acts like tuning your internal clock, reducing the chance of disruptive wake-sleep overlaps — much like ensuring all parts of an orchestra are synchronized for perfect harmony,' Walker said.
Also prioritize stress management, by using, for example, mindfulness and relaxation exercises, Walker said. Therapies can relieve certain underlying issues triggering sleep paralysis, including cognitive behavioural therapy, especially the version for people with insomnia.
In more serious situations, medications are sometimes used, Walker said. Those include SSRI (selective serotonin reuptake inhibitor) or tricyclic antidepressants that can help manage a smooth flow between sleep stages or even reduce the REM phase of sleep.
Generally, boosting the brain's serotonin levels somehow compensates for the loss of the REM phase, Jalal said. But rarely, long-term antidepressant use has been linked with REM sleep behaviour disorder.
While the aforementioned treatments can help reduce the frequency or length of sleep paralysis episodes, there isn't yet a gold-standard treatment that can stop an episode once it's happening.
Jalal has been trying to officially create one over the past decade, though, and it's self-inspired. Called meditation relaxation therapy, the treatment reduced sleep paralysis by 50% after eight weeks for six people with narcolepsy, compared with a control group of four participants, found a small pilot study Jalal published in 2020. He currently has another study of the same treatment with more participants underway at Harvard. And the steps of Jalal's therapy are as follows:
Cognitively reappraise the meaning of the attack. Close your eyes and remind yourself that your experience is common and you won't die from it.
Emotionally distance yourself from it. Tell yourself that since your brain is just playing tricks on you, there's no reason for you to be scared or risk the situation getting worse because of your own negative expectations.
Focus on something positive. Whether it's praying or imagining a loved one's face, this refocusing can make thoughts more pleasant rather than monstrous.
Relax your muscles and don't move. Some experts say trying to slightly move your fingers or toes one by one may help you come out of an episode sooner. But Jalal's fourth step advises against this movement since you'd still be sending signals to paralyzed muscles and maybe triggering hallucinations.
Viewing your own biology in a more objective way by learning more about the scientific basis of sleep paralysis is also helpful, Jalal said.