What Is a Sleep Paralysis Demon?

You’re sleeping when suddenly something is smothering you. You attempt to get free but can’t move your arms or legs. An evil entity has pinned you beneath its crushing weight.

If this sounds terrifyingly familiar, you’ve likely had a visit from a “sleep paralysis demon.” Though it sounds like it came straight out of a horror movie, sleep paralysis with the hallucination of a demon is a reality for an estimated 8% of the population. Some studies found the spooky experience even more common, with 30% of people reporting at least one incident in their lifetime.

A sleep paralysis demon is a hallucination that occurs when you’re transitioning out of sleep. During the lifelike dreams of rapid eye movement (REM) sleep, your voluntary muscle movements are immobilized so that you don't act out your dreams. Most of the time, this so-called paralysis is helpful, but occasionally, your brain becomes somewhat awakened during the transition from REM to wakefulness.

During this period, you may sense or even see a malevolent presence lurking nearby or hovering over you. You may also feel as if the presence is pressing down on your chest or somehow attacking you. That is a sleep paralysis demon.

Understandably, the experience can be terrifying. In such a vulnerable and not fully aware state, it can be hard to differentiate hallucination from reality. But rest assured, you are not starring in your own horror show. The mind is a fascinating thing, and sometimes, it plays tricks on us, giving us the fright of our lives. Keep reading to find out the science behind what’s happening in the brain during this frightening phenomenon and what you can do to prevent the situation from happening again.

Because sleep paralysis demons are linked to disrupted REM sleep and abrupt awakenings, the quality of your sleep surface can play a supporting role in how smoothly the brain moves between sleep stages. A mattress that promotes consistent comfort, proper body alignment and minimal pressure or tossing and turning may help reduce sleep fragmentation that can interrupt REM sleep. While a mattress cannot cause or cure sleep paralysis on its own, creating a more stable, uninterrupted sleep environment may lower some of the conditions that allow these vivid hallucinations to occur.

The so-called sleep paralysis demon—which can manifest as a witch, evil spirit or other creature—isn’t new or isolated to a specific region. Many cultures refer to the condition as the “incubus phenomenon.” The term “incubus” is Latin for night hag or nightmare. Ancient Greek culture even gendered the demons, with incubus referring to a demon disguised as a man pressing down on a sleeping woman and succubus describing a demon disguised as a woman pressing down on a sleeping man.

Incubi and succubi have been referenced for hundreds of years and have countless names. More than 100 cultures have their own descriptions, many of which align with regional folklore, for the unsettling experience of sleep paralysis. Here are a few.

• One early reference to sleep paralysis stems from about 400 B.C., in ancient Greece, where references are found to “Pan ephialtes,” a horned god that could “pounce upon someone” in their dreams.  
• Another early reference to a succubus harkens back to 2400 B.C., when a “she-demon” was called “Lilith” or “Lilitu,” stemming from Mesopotamian and Jewish mythology.  
• In Catalan folklore, the demon is more like a malevolent dog or cat called “Pesanta,” known for breaking into houses at night where it “steps over people’s chests, disturbing their breath and causing nightmares.”  
• In Korean culture, ‘Ha-wi-nulia” roughly translates to “being squeezed by scissors.”  
• In Newfoundland, the sleep paralysis phenomenon is called Old Hag. The assailant is said to be an old hag “who can put it on you like a charm.”  
• In Brazil, “Pisadeira” is the hallucinated entity, which folklore describes as a long-fingernailed crone who “tramples on the chest of those who sleep on a full stomach with the belly up.”  
• The Dutch have referred to the demon as the “Night-Mare.”  
• Old English features the word “mære,” referencing a female spirit who suffocates people in their sleep.  
• In Germany, the term is “hexendrücken,” which means “witch’s pressing.”  
• In France, people call the demon “cauchemar.”  
• In Southeast Asia, people fear the “dab tsog,” a nightmare spirit.  
• The Yoruba people of Nigeria call the experience “ogun oru,” which translates to “nocturnal warfare.” This term is also used for epileptic seizures.  
• In Egypt, the spiritual creature is known as a “Jinn.”   
• In China, some people refer to sleep paralysis as “ghost oppression.”  
• In Japan, the sleep paralysis phenomenon gets the term “kanashibari,” translating to “bound in metal.”  
• Mexico calls the experience “Se me subió el muerto,” translating to “a dead body climbed on top of me.”  
• In Iran, the experience is called “Kabus,” or a heavy presence lurking on one’s chest, causing breathing difficulty.  
• The Inuit People in the subarctic regions of Canada refer to the horror as “uqumangirniq,” in which shamans are responsible for casting spells on people who sleep.  
• Cambodian people have called the imaginary entity “khmaoch sângkât” or “the ghost that pushes you down.”   
• In Thailand, “phi am” is a “ghost that haunts subjects when half-asleep and unable to move.”  
• In Saint Lucia, the term is “Kokma,” which is described as “attacks by dead spirits or unbaptized babies that jump into a body and squeeze the throat.”  
• In Ethiopia, the evil spirit that haunts you in your sleep is called “dukak.”  
• In the Tanzanian archipelago of Zanzibar, “Popobawa” is the evil entity.  
• In the United Kingdom, a myth says that a spirit is trying to get into your body during sleep, but it fails to do so while you’re waking.  
• In some parts of the U.S., people describe a witch straddling their chest.  

Often, sleep paralysis is mentioned as a way of explaining the unexplained, such as paranormal activity or even alien abductions. Sleep paralysis demons appear in art, including “The Nightmare,” an 18th-century painting by Swiss artist Henry Fuseli, and works by Francis Bacon and Francisco Goya.

The demon has also been a common theme of television shows, such as “American Horror Story,” and countless novels and movies. The 2018 horror movie “Mara,” directed by Clive Tonge, depicts a criminal psychologist who is investigating the murder of a man in his sleep. She then experiences the haunting of a sleep-paralysis demon herself.

Much of the powerless feeling of sleep paralysis comes from the physical nature of the experience—the inability to move our muscles in the moment to react to the situation.

During REM sleep, which is the last phase of each sleep cycle, we tend to dream. So that we do not enact our dreams, our brain essentially paralyzes our muscles during this phase, suppressing muscle tone and inhibiting the neurons in the spinal cord.

Eventually, we transition from REM sleep to being awake and aware. However, sleep paralysis occurs when you gain some awareness of your surroundings mentally but are still physically motionless due to the paralyzing effects of the REM phase. Think of it like transitioning spaces: You are midway through exiting one room (REM sleep) but have not yet fully entered the next (being awake).

We’re all prone to visual, auditory and sensory hallucinations, both when we’re falling asleep and when we’re waking up. When it comes to symptoms of sleep paralysis, this can include a sense that an intruder is near you—a hallucination.

Hypnagogic hallucinations occur when we’re slipping into the first phase of sleep, which is non-REM (NREM). You might see a kaleidoscope of colors or patterns, for example, or you might experience a sense of falling and then accidentally jerk yourself awake, a phenomenon called hypnic jerks. Hypnopompic hallucinations, on the other hand, occur when we’re waking up and transitioning out of REM sleep; they are often continuations of dreams.

A sleep paralysis demon is a hypnopompic hallucination. The demons often take the shape of childhood fairytale villains, such as witches, ghosts, beasts or other ominous creatures.

Though more research is needed to understand exactly why people so commonly hallucinate seeing demons, researchers theorize that people see a humanoid figure over them because of a momentary lapse in how the brain processes bodily perception. When we’re awake, the parietal lobe sends us information about our body parts and their positions and movements. This info helps us understand where we are in relation to objects, so we don’t constantly bump into doorframes or coffee tables, for example. During sleep paralysis hallucinations, that valuable info called proprioception and other sensory input gets muddled, and we see a highly distorted projection of our brain’s stored body image. It’s like we’re looking into a mirror but seeing a monster.

Fear gets amplified in this state. The intense terror likely occurs because the amygdala, known as the fear center of the brain, is highly activated during REM sleep. The hyperactivity of the amygdala is why dreams can be so intense. Throughout the waking day, if you encounter a potential threat, you can quickly assess whether the threat is legitimate and react accordingly, thanks to your brain’s logic-regulating abilities of the prefrontal cortex, which is dormant while you sleep. But during REM sleep, your brain lacks the information to correctly assess whether a threat is real. So, during a “visit” from a sleep paralysis demon, nothing reassures you that it’s only a dream.

Symptoms of the sleep paralysis demon phenomenon are somewhat different for each person who experiences it. However, some commonalities exist, such as:

• being terrified  
• feeling immobilized or unable to move  
• seeing a demon or entity  
• sensing a presence on the chest  
• feeling like you can’t breathe  
• smelling an odor  
• hearing strange sounds  
• experiencing the sensation of choking  
• experiencing chest pain and discomfort  
• experiencing heart palpitations  
• experiencing numbness or tingling  
• feeling cold or hot  
• having abdominal pain or an upset stomach  
• feeling dizzy, lightheaded or as if you’re spinning  
• sweating  
• shaking 

Although the demon itself is not real, the experience of hallucinating a sleep paralysis demon can be horrifying enough to have lasting effects on your sleep. If you endure the sleep paralysis demon phenomenon often, you may understandably develop a fear of going to bed, which could then lead to insomnia and even long-term anxiety. Both insomnia and anxiety are associated with experiencing sleep paralysis demons.

Additionally, enduring this type of terror in the middle of the night can cause disrupted sleep, breaking up your transition to your next sleep cycle and keeping you awake if you’re unable to fall back asleep.