Researchers believe that these hallucinations may have fueled belief in witches in modern Europe, and could even explain some claims of alien abductions.

What is known about the phenomenon?

Scientists believe that sleep paralysis has probably been around for as long as humans slept.

There are various colorful descriptions of these episodes throughout literary history.

Mary Shelley, the British playwright best known for authoring the gothic novel Frankenstein, was inspired by a painting depicting an episode of sleep paralysis to write a scene for the play.

But the truth is that, until now, little research has been done on this rare condition.

“It’s been an ignored phenomenon… but in the last 10 years there’s been increasing interest,” says Baland Jalal, a sleep researcher at Harvard University, who in 2020 completed the first clinical trial on different ways to treat paralysis. of the dream

His goal is to more solidly understand the causes and effects of this and to discover what it tells us about the broader mysteries of the human brain.

But in 2011, clinical psychologist Brian Sharpless, currently an associate professor at St Mary’s College of Maryland, conducted the most comprehensive review to date of the prevalence of the condition in people.

It examined data from 35 studies spanning five decades. Together, they included more than 36,000 volunteers.

Sharpless found that sleep paralysis was more common than previously thought, with almost 8% of adults claiming to have experienced it at some point. That number is much higher among college students (28%) and psychiatric patients (32%).

“It’s not that uncommon,” says Sharpless, who is also a co-author of “Sleep Paralysis: Historical, Psychological, and Medical Perspectives.”

How is it explained?

After experiencing the phenomenon, some people try to understand what happened to them with supernatural or even paranormal explanations.

In reality, says Jalal, the cause is much more mundane.

At night, our body goes through four stages of sleep. The final stage is called Rapid Eye Movement or REM sleep. This is when we dream.

During REM, your brain paralyzes your muscles, probably to prevent you from acting out physically in your dreams and getting hurt. But sometimes, and scientists are still not sure why, the sensory part of the brain emerges from REM prematurely.

“The sensory part of the brain is activated,” says Jalal. “You’re waking up mentally, perceptually, but physically you’re still paralyzed,” he adds.

When I was in my early twenties, I would experience sleep paralysis every two or three nights, but even then, it didn’t have much of an impact on my life. It was an interesting anecdote for friends and family. In that sense, my experience was common.

“For most people, it’s a peculiar thing that they live with,” says Colin Espie, professor of sleep medicine at the University of Oxford.

“It’s a bit like sleepwalking: most people who sleepwalk never see a doctor. It’s a curiosity in the family, a topic of conversation.”

But for an unfortunate minority, the condition is not so anecdotal.

Sharpless’s research found that between 15% and 44% of people with sleep paralysis experience “clinically significant distress” as a result.

The problems usually stem from how we respond to sleep paralysis, rather than the condition itself. Patients obsess all day about when the next episode might occur.

“It can be anxiety-inducing at the beginning and end of the night,” says Espie.

“And you grow a web of worry and restlessness around you. The worst expression of that is a kind of panic attack.”

Doctors assert that sleep deprivation increases the likelihood of experiencing paralysis because it fragments sleep architecture. Some patients report that lying on their back increases the chances of paralysis, although the reason for this remains unclear.

To treat sleep paralysis, the most prevalent approach involves educating patients by teaching them about the science behind the condition and providing reassurance that they are not in any danger.

Sometimes a form of meditation therapy is used. The goal is to reduce the patient’s anxiety about going to bed and train them to remain calm when sleep paralysis occurs.

In more severe cases, doctors may consider prescribing medications, including selective serotonin reuptake inhibitors (SSRIs). SSRIs are usually used to treat depression, but they have the side effect of suppressing REM sleep.

The most dramatic and memorable episodes of sleep paralysis are usually the ones that come with vivid hallucinations.

These night visions are often a source of fear, but scientists also believe they can tell us fascinating things about the human brain.

But the muscles are paralyzed, so the brain doesn’t get any feedback signals in return.

“There is an incongruity… the self is fragmented, degraded,” says Jalal.

As a result, the brain “fills in the gap” and creates an explanation for why the muscles can’t move. That’s why so many hallucinations involve a creature sitting on your chest or holding your body.

The brain, a “story-telling machine”

This reinforces the idea, popular among evolutionary scientists, of the human brain as a “story-telling machine.”

We struggle to come to terms with the fact that much of the world is random, so our brains create dramatic narratives to find meaning in the mundane.

Christopher French, head of the anomalous psychology research unit at Goldsmiths, University of London, has spent more than a decade talking to people around the world who have experienced these hallucinations and recording what they saw.

“There are common themes, but there’s also a lot of idiosyncrasies, variability,” French says.

Culture heavily influences other behaviors that are much more common.

On the island of Newfoundland in Canada, it is common for people to see an “old hag” sitting on their chests.

Mexicans, meanwhile, usually hallucinate with a “dead man” lying on their chest, while those from Saint Lucia speak of “korma”, the souls of unbaptized children. And the Turks imagine the “Karabasan”, a mysterious and ghostly creature.

This reinforces the idea that humans are overwhelmingly social animals, heavily influenced by culture and expectations.

In fact, in a series of studies, Jalal compared symptoms in Denmark and Egypt, among volunteers with a similar age and gender distribution, and found a cultural gulf in the way sleep paralysis manifested itself.

Egyptians were much more likely than Danes to have experienced sleep paralysis ( 44% compared to 25% ), and more likely to support a supernatural explanation.

“When you have anxiety and stress, your sleep architecture becomes more fragmented, so you’re more likely to have sleep paralysis,” he says.

Your grandmother’s description of the creature, which appears at night and attacks, causes hyper-arousal in you and hyper-alertness in the fear centers of your brain. And during REM sleep you feel, ‘oh, something’s wrong, I can’t move, the creature is here'”.

“It seems that culture can create this amazing effect,” he concludes.