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Body + BrainBody & Brain

The Nightmare of Sleep Paralysis

Neuroscientists are discovering that there may be more to sleep paralysis than we once thought.

ByAnnette ChoiNOVA NextNOVA Next
The Nightmare of Sleep Paralysis

“I was facing my clothes rack where I have a bunch of stuff hanging off of it,” Brandon Tan says. “And since it was dark, my bags and jackets were kind of morphed into black figures.”

Tan, a New York City-based writer, says that that night—with eyes wide-open and lips sealed—he struggled to move his own body. Quickly, nightmarish hallucinations began taking over his auditory and sensory perceptions, blurring the line between dream and reality. “I just kept hearing really mischievous giggling and really creepy screaming,” he says. “And it felt like there were really strong gusts of wind in my room, but the window was completely shut.”

Jackie Monoson can sympathize. But unlike Tan, who is new to the experience of sleep paralysis, Monoson, a video editor living in New York City, says she has experienced it on and off for several years now, especially during times of high stress. She recalls one episode in particular, which occurred during finals week of her senior year at New York University: “I felt like as I was falling asleep, I was also waking up,” she says. “I was in my dorm, and I knew that my roommate was in the room, but I couldn’t yell out.”

Not long after her first few encounters, Monoson turned to the internet for help. Per the advice of an online sleep paralysis forum, during episodes, Monoson learned to focus on moving smaller muscles—like wiggling her toes—to break from the feeling of paralysis.

Sleep paralysis affects millions every year, and studies estimate that more than half of the global population will experience at least one episode in their lifetimes. Despite the prevalence, however, the disorder is poorly understood.

Baland Jalal, a neuroscientist at the University of Cambridge and current fellow at Harvard University, says the lack of scientific research into sleep paralysis likely stems from a place of confusion—no one really knows what to make of it.

“People understand what it means to have OCD and to wash your hands several times a day,” Jalal says, “But what does it mean if somebody saw a ghost in their room?”

Now, though, neuroscientists like Jalal are diving in and discovering that there may be more to sleep paralysis and its opposite—known as REM sleep disorder—than we thought. What for many years has been brushed off as no more than a bad dream or perhaps a trick of the moonlight might help us unlock what happens in our brains during sleep.

What is Sleep Paralysis?

Though we don’t know much about the details of sleep paralysis, we do know the basics. It happens when falling asleep or waking up. During an episode, a person becomes aware of their surroundings but is unable to move or speak. It’s like the mind is wide-awake, but the body didn’t get the memo.

During a sleep cycle, which typically lasts one to two hours, our brains traverse five stages. The first four make up non-rapid eye movement (NREM) sleep. The fifth and final stage is when REM takes place. It is also when sleep paralysis sets in. REM, which occurs approximately 90 minutes into a sleep cycle, is when the brain is most active, producing the most vivid and emotionally-charged dreams. “If you look at the pattern of neural activity in someone in REM sleep and compare that guy to a wakeful person, the brains of these two people look indistinguishable,” Jalal says. “Occasionally, the brain of the guy in REM looks more active than the guy who is awake.”

During sleep paralysis, a chilling sense of suffocation sets in.

During REM, our body regularly inhibits its motor neurons, paralyzing itself to prevent us from acting out REM’s elaborate visions and causing harm. Normally, the person is immersed in sleep and doesn’t notice they can’t move. Individuals with sleep paralysis, though, are wholly aware of their immobility. Panicky, unsuccessful efforts to sit upright or lift an arm can make things worse, making people’s bodies stiff or exacerbating pressure points.

Breathing also factors in—when awake, breathing patterns are typically irregular because they’re affected by speech, emotion, and exercise. But in REM, the body is in full control. So during sleep paralysis when people instinctually try to regain control of their breathing and realize they can’t, a chilling sense of suffocation sets in.

Combined, these symptoms create an overwhelming fear that our brains can’t ignore. When awake, the amygdala—the emotion and threat center of the brain—quickly confirms or rejects feelings of danger. However, during sleep paralysis, the amygdala doesn’t have the right information to determine whether or not a threat is genuine. Unsure of what dangers to believe, the subject is left feeling vulnerable and helpless.

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Supernatural Theories

It would be easy to dismiss sleep paralysis as a side-effect of our sleep-deprived society, but the phenomenon isn’t limited to the United States. Globally there are over 100 words—in various languages—used to describe sleep paralysis. Generations of people have attributed their experiences to everything from alien abductions to parasitic attacks. Different countries associate sleep paralysis with varied levels of danger. And research has found that the more threatened people are by sleep paralysis, the likelier the episodes are to reoccur.

Culture seems to play a role. Consider the differences in sleep paralysis between Denmark and Egypt, for example: Danes have a very mild aversion to the sleep paralysis and brush the episodes off as trivial incidents, Jalal says. On the other hand, in Egypt, there’s an overwhelming fear of death by sleep paralysis. He says the story of Jinn, the spirit-like being that torments victims when the body is powerless, instills both a psychological and conditioned physiological fear that makes Egyptians more susceptible to waking up during REM. This leads to longer, more intense, and—most importantly—cyclic episodes. As a result, Jalal has found that sleepers in Cairo were three times more likely than those in Copenhagen to experience sleep paralysis.

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Psychologists and neuroscientists are trying to disrupt and prevent sleep paralysis in Egypt by using culturally adapted cognitive behavioral therapy (CA-CBT). By utilizing psycho-social interventions, which hone in on emotional and social therapy methods, experts are trying to modify cultural perceptions about sleep paralysis. So far, the results are inconclusive.

Sleep paralysis is similarly distressing in other cultures. Take the Caribbean myth of kokma , where the souls of unbaptized babies roam around, smothering slumberers. The Turkish call it karabasan , during which sufferers are visited by demons. During a typical episode of karabasan , the Turks say a wicked, supernatural entity wearing a wide-brimmed hat enters into the room and strangles the victim with its hands. Snatching the hat, according to some versions of the story, is the only way to prevent the spirit from returning.

Glitch of the Brain

Ordinary triggers like sleep deprivation, increased stress, and irregular sleep patterns can prompt sleep paralysis—which explains why the phenomenon is most common in students and individuals with mental health disorders.

It’s common for people to keep their sleep paralysis experiences to themselves.

Last May, Dan Denis, postdoctoral student in the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center, found that sleep paralysis is most prevalent in individuals with anxiety-specific conditions like post-traumatic stress disorder and panic disorder. In his literature review , Denis and his colleagues investigated the relationship between sleep paralysis and its associated variables including substance use, stress and trauma, genetic influences, and personality. After analyzing hereditary factors, the team also found genetic risk to be a factor for higher rates of sleep paralysis.

“Asians in the U.S. have very high rates,” Jalal says, “White people have the least rates. So there’s certainly a genetic component that plays in.”

Denis says yet another reason why sleep paralysis is under-researched is because it’s common for people to keep their sleep paralysis experiences to themselves. “They might feel nervous to talk about it. And when they do talk about it, a lot of doctors and medical professionals haven’t heard of it or aren’t sure what it is.”

Maybe Rats Can Help

At the University of Toronto, neuroscientists have turned to rats for answers. By measuring the electrical activity in facial muscles of rats experiencing sleep paralysis, they identified the neurotransmitter and receptor mechanisms responsible.

The team found that two brain chemical systems, gamma-aminobutyric acid (GABA) and glycine, were working together to cause muscle paralysis during REM. Studying these chemicals’ role in sleep paralysis could help us better understand the disorder and its counterparts, including REM sleep disorder, says John Peever, a neuroscientist and author of the study. REM sleep disorder, as opposed to sleep paralysis, can lead to physical—and sometimes violent—enactments of intense REM dreams.

More troubling, according to Peever, the team found that “ 80% of people who have [REM sleep disorder] eventually develop a neurodegenerative disease, such as Parkinson’s disease.” Studying GABA and glycine could give scientists windows into understanding and eventually treating these diseases.

Peever says that he has studies currently under review that look at what parts of the brain seem to glitch during REM sleep disorder and cause the uncontrollable movement. He says that understanding both the roles of neurotransmitters and the brain processes involved in sleep-related paralysis would allow scientists to figure out how to alter the systems to help prevent sleep disorders across the spectrum.

Exploring Treatments

Today, though, treatment for REM sleep disorder is hard to come by. It is abundantly clear to anyone who runs a quick Google search that there isn’t much out there. The most recommended remedy is a general dose of “improved sleep hygiene.”

Some studies have attempted to treat sleep paralysis in a roundabout way. Trials for gamma hydroxybutyrate, an anti-sleep medication, have been conducted to treat individuals with narcolepsy, a disorder that causes excessive drowsiness throughout the day. Because sleep paralysis is a common symptom of narcolepsy, the trials did show some promise. Yet there haven’t been any official drug tests specifically for patients with sleep paralysis.

Sleep paralysis can unlock secrets about sleep.

Jalal is trying something else, and it seems to be working. In an effort to reduce the anxiety brought on by sleep paralysis, Jalal developed one of the first-ever systemic therapies called Meditation-Relaxation Therapy , or MR. The first of the four-step process is what Jalal calls “reappraisal of situation.” It’s a test of willpower that requires the person to develop an objective stance on the situation. “Tell yourself it’s temporary,” he says. The next two steps call for an emotional and psychological distancing from the paralysis. By focusing on something positive, one subverts the perception of inevitable catastrophe.

“The brain has limited attention capacities. You can only attend to so many things in your environment,” Jalal says. “So by focusing all the attention on something positive, it’s very hard to attend to negative bodily stimuli.”

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The final step is muscle relaxation. Despite the natural reaction to resist the feeling of paralysis, Jalal recommends loosening up and simply waiting for the moment to pass. Ultimately Jalal hopes that, by psychologically distancing themselves from the uneasy sensations, individuals with sleep paralysis will develop new circuits in their brains. With consistency, his mindfulness techniques should make the episodes more bearable. Eventually, he predicts that episodes will pass with ease.

Jalal believes MR could help other sleep disorders like insomnia and nightmare sleep disorder, too. “You basically challenge some of the catastrophic cognitions and fear imagery that may contribute to nightmares.”

“Sleep paralysis can unlock secrets about sleep and particularly how the transitioning of REM sleep and non-REM sleep occurs,” Jalal says.
And though there is currently no magic pill to cure sleep paralysis, by better understanding its components—REM sleep and the shutdown of muscle movement—a definite treatment for the enigmatic condition may not be far off.

“The first time you kind of hear about it, it doesn’t really sound like a real thing,” says Denis, the sleep and cognition postdoc. “It sounds like something crazy, like horror movie kind of story.”

Photo credit: Lisa Murray / Flickr (CC BY-ND 2.0) , Public Domain