What sleep paralysis feels like: Terrifying, like you're trapped with a demon on your chest

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This feature is part of a National Post series by health reporter Sharon Kirkey on what is keeping us up at night. In the series, Kirkey talks to sleep scientists and brain researchers to explore our obsession with sleep, the seeming lack of it and how we can rest easier.

Psychologist Brian Sharpless has been a horror movie buff since watching 1974’s It’s Alive! on HBO, a cult classic about a fanged and sharp-clawed mutant baby with a proclivity to kill whenever it got upset.

In his new book, Monsters on the Couch: The Real Psychological Disorders Behind Your Favorite Horror Movies, Sharpless devotes a full chapter to a surprisingly common human sleep experience that has been worked into so many movie plots “it now constitutes its own sub-genre of horror.”

Not full sleep, exactly, but rather a state stuck between sleep and wakefulness that follows a reliable pattern: People suddenly wake but cannot move because all major muscles are paralyzed.

The paralysis is often accompanied by the sensed presence of another, human or otherwise. The most eerie episodes involve striking hallucinations. Sharpless once hallucinated a “serpentine-necked monstrosity” lurking in the silvery moonlight seeping through the slats of his bedroom window blind.

Feeling pressure on the chest or a heavy weight on the ribs is also common. People feel as if they’re being smothered. They might also sweat, tremble or shake, but are “trapped,” unable to move their arms or legs, yell or scream. The experience can last seconds, or up to 20 minutes, “with a mean duration of six minutes,” Sharpless shared with non-sleep specialists in his doctor’s guide to sleep paralysis.

Sleep paralysis is a parasomnia, a sleep disorder that at least eight per cent of the general population will experience at least once in their lifetime. That low-ball estimate is higher still among university students (28 per cent) and those with a psychiatric condition (32 per cent). It’s usually harmless, but the combination of a waking nightmare and temporary paralysis can make for a “very unpleasant experience,” Sharpless advised clinicians, “one that may not be easily understood by patients.”

“Patients may instead use other non-medical explanations to make sense of it,” such as, say, some kind of alien, spiritual or demonic attack.

Eight years into studying sleep paralysis and with hundreds of interviews with experiencers under his belt, Sharpless had never once experienced the phenomenon himself, until 2015, the year he published his first book, Sleep Paralysis, with Dr. Karl Doghramji, a professor of psychiatry at Thomas Jefferson University. Sharpless woke at 2 a.m. and saw shadows in the hallway mingling and melding into a snake-like form with a freakishly long neck and eyes that glowed red. When he attempted to lift his head to get a better look, “I came to the uncomfortable realization I couldn’t move,” Sharpless recounts in Monsters on the Couch. “Oh my God, you’re having sleep paralysis,” he remembers thinking when he began to think rationally again.

“It’s an unusual experience that a lot of folks have,” Sharpless said in an interview with the National Post. The hallucinatory elements “that tap into a lot of paranormal and supernatural beliefs” is partly what makes it so fascinating, he said. Several celebrities — supermodel Kendall Jenner, American singer-songwriter and Apple Music’s 2024 Artist of the Year Billie Eilish, English actor and Spider-Man star Tom Holland — have also been open about their sleep paralysis.

You're seeing, smelling, hearing something that isn't there but feels like it is

Brian Sharpless, psychologist

It has a role in culture and folklore as well. In Brazilian folklore, the “Pisadeira” is a long-finger-nailed crone “who lurks on rooftops at night” and tramples on people lying belly up. Newfoundlanders called sleep paralysis an attack of the “Old Hag.” Sleep paralysis has been recognized by scholars and doctors since the ancient Greeks, Sharplesss said. Too much blood, different lunar phases, upset gastrointestinal tracts — all were thought to trigger bouts of sleep paralysis. Episodes have been described in the Salem Witch Trials in 1692. The Nightmare, a 1781 oil painting by Swiss artist Henry Fuseli of a woman in deep sleep, arms flung over her head and an incubus, a male demon, on her belly, has been taken as a symbol of sleep paralysis, among other interpretations. Sleep paralysis figures in numerous scary films and docu-horrors, including Shadow People, Dead Awake, Haunting of Hill House, Be Afraid, Slumber and The Nightmare.

The wildest story Sharpless has heard involved an undergrad student at Pennsylvania State University who was sleeping in her dormitory bunk bed when she woke suddenly, moved her eyes to the left and saw a child vampire with blood coming out of her mouth.

“The vampire girl ripped her covers off, grabbed her by the leg and started screaming, ‘I’m dragging you to hell, I’m dragging you to hell,’ pulling her out of the bed, all the while blood is coming out of her mouth,” Sharpless recalled the student telling him.

When she was able to move again, she found herself fully covered, her leg still under the blankets and not hanging off the ledge of the bunk bed as she imagined.

With sleep paralysis, hallucinations evaporate the moment movement returns, Sharpless said.

People are immobile in the first place because, during REM sleep, when dreams tend to be the most vivid and emotion-rich, muscles that move the eyes and involve breathing keep moving but most other muscles do not. The relaxed muscle tone keeps people from acting out their dreams and potentially injuring themselves or a bedmate.

“In REM, if you’re dreaming that you’re running or playing the piano, the brain is sending commands to your muscles as if you were awake,” said Antonio Zadra, a professor of psychology and a sleep scientist at Université de Montréal.

More than a decade ago, University of Toronto neuroscientists Patricia Brooks and John Peever found that two distinct brain chemicals worked together to switch off motor neurons communicating those brain messages to move. The result: muscle atonia or that REM sleep muscle paralysis. With REM sleep behaviour disorder, another parasomnia, the circuit isn’t switched off to inhibit muscle movement. People can act out their dreams, flailing, kicking, sitting up or even leaving the bed.

Normally, when people wake out of REM sleep, the paralysis that accompanies REM also stops. With sleep paralysis, the atonia carries over into wakefulness.

“You’re experiencing two aspects of REM sleep, namely, the paralysis and any dream activity, but now going on while the person is fully awake,” Sharpless said. People have normal waking consciousness. They think just like they can when fully awake. But they’re also experiencing “dreams” and because they’re awake, the dreams are hallucinations that feel just as real as anything in waking life.

Sleep paralysis tends to happen most often when people sleep in supine (on their back) positions and, while Sharpless and colleagues found that about 23 per cent of 172 adults with recurrent sleep paralysis surveyed reported always, mostly or sometimes pleasant experiences — some felt as if they were floating or flying — the hallucinations, like the beast Sharpless conjured up, are almost always threatening and bizarre.

Why so negative?

Evolution primed humans to be afraid of the dark and, in general, when we wake up, “It’s not usual for us to be paralyzed,” Sharpless said. “That’s an unusual experience from the get-go.” Sometimes people have catastrophizing thoughts like, “Oh my god, I’m having a stroke,” or they fear they’re going to die or be forever paralyzed.

“If you start having the hallucinatory REM sleep-dream activity going on, then it can get even worse,” Sharpless said.

Should people sense a presence in the room, the brain organizes that sensed presence into an actual shape or object, usually an intruder, attacker or something else scary, like an evil force. “If it goes on, you might actually make physical contact with the hallucination: You could feel that you’re being touched. You might smell it; you might hear it,” Sharpless said.

These aren’t nightmares. With nightmares, people aren’t aware of their bedroom surroundings and they certainly can’t move their eyes around the room.

What might explain that dense pressure on the chest, like you’re being suffocated or smothered? People are more likely to experience breathing disruptions when they’re sleeping on their backs. People with sleep apnea are also more likely to experience bouts of sleep paralysis because of disrupted oxygen levels, and the fact that they are awake, temporarily paralyzed and in a not so positive state, can affect respiration. Rates of sleep paralysis are higher in other sleep disorders as well, narcolepsy especially.

While sleep paralysis can be weird and seriously uncomfortable, Sharpless marvels in Monsters on the Couch at how often people have asked him how one might be able to induce sleep paralysis.

One way is to have messed up sleep. Anything that disrupts sleep seems to increase the odds, Sharpless said, like sleep deprivation, jet lag, erratic sleep schedules. Sleep paralysis has also been linked to “exploding head syndrome,” a sleep disorder Sharpless has published a good bit on. People experience auditory hallucinations — loud bangs or explosions that last a mere second — during sleep-wake transitions.

How can people snap out of sleep paralysis?

In a survey of 156 university students with sleep paralysis, some of the more effective “disruption techniques” involved trying to move smaller body parts like fingers or toes, and trying to calm down or relax in the moment.

One review of 42 studies linked a history of trauma, a higher body mass index and chronic pain with episodes of fearful sleep paralysis. Excessive daytime sleepiness, excessively short (fewer than six hours) or excessively long (longer than nine hours) sleep duration have also been implicated.

To reduce the risk, Sharpless recommends good sleep hygiene, including going to bed and waking up at the same time, not drinking alcohol or caffeine too close to bedtime and “taking care of any issues you’ve been avoiding,” especially anxiety, depression or trauma. One simple suggestion: try to sleep on your side. “If you have a partner, have them gently roll you over,” Sharpless said. Zadra, author, with Robert Stickgold, of When Brains Dream: Exploring the Science and Mystery of Sleep, recommends trying to move the tongue to disengage motor paralysis. “The tongue is not paralyzed in REM sleep. Technically, you can move it,” Zadra said. Even thinking about moving the tongue or toes can put people into a whole different mindset “rather this feeling of panic and not being able to move at all,” said Zadra.

Once awake, most people realize, “Whoa, that was weird” and go about their lives, but others might develop a conditioned fear response to their bedroom, Sharpless said. People might fear going to sleep. “For those folks it could be a problem,” and a reason to seek help. First, people need to be reassured it’s not dangerous and that they aren’t going crazy. Drug therapy is rarely necessary but can be an option. Certain anti-depressants can suppress REM sleep. Sharpless and Doghramji published the first treatment manual for isolated sleep paralysis that consists of a short (five-sessions) course of cognitive behavioural therapy.

People who believe in supernatural or paranormal things are more likely to experience sleep paralysis but whether it’s a chicken-or-egg thing, a cause or consequence of sleep paralysis, Sharpless isn’t so sure.

“It’s a weird event, right? I frankly don’t begrudge anybody for firmly believing something strange happened, even if it doesn’t seem scientifically possible,” he said.

“You’re seeing, smelling, hearing something that isn’t there but feels like it is. You can be convinced.”

National Post