For the 8 percent of the general population who experience it, it's unforgettable: the realization behind heavy-lidded eyes that you are asleep, yet awake at the same time. You find yourself totally unable to move, cry out, or even whimper.
The fear creeps in, gripping your entire being as you try to wake yourself, but no matter how much willpower and effort you put forth into trying to move a finger, whisper for help, or roll out of bed to slam your body onto the floor, you're absolutely trapped.
You are a prisoner in your body. You cannot even breathe loudly enough to alert the person next to you.
And then the real fear comes.
You sense someone — or something — else in the room, watching you, creeping toward you, perhaps even pinning you down. You can do nothing. You cannot escape. You cannot cry out. You cannot move. It whispers to you in a song both melodic and dark with the mocking voice of childhood fear.
And then suddenly, you burst into waking as if you've been smashed back to Earth, the room spinning as the tendrils of darkness slip from your frozen, sweat-glistened limbs.
You gasp for air. You look around, filled with terror, afraid to close your eyes. When you do, you feel the paralysis creeping back over your body, forcing you to get back up, turn on the lights, and try to shake off the nightmare that casts a long shadow over both the psychological and physical worlds.
We explored the internet to bring you some facts and experiences about this unsettling phenomenon to shed some light on the subject.
1. Paralysis and the most vivid dreams occur during the same sleep phase.
"In normal sleep, this paralysis ceases before the sleeper becomes consciously awake. Sometimes, however, the process falls out of step. A person may enter a state of waking conscious and become aware of their body while the body itself is still paralysed. In some cases, the combination of wakeful and dream consciousness can cause frightening and convincing hallucinations."
2. Believe it or not, paralysis may serve a purpose.
According to research conducted by University of Toronto neuroscientists Patricia L. Brooks and John H. Peever, the brain releases two neurotransmitters — gamma-aminobutyric acid (GABA) and glycine — that induce muscle atonia during the onset of REM sleep.
The paralysis keeps us from physically acting out our dreams, which could lead to injury.
Whatthefat explains and offers one theory as to why the brain does this:
"During dreams, the brain seems to actually be simulating scenarios and responding to them as though it were awake.Why it does this is an extraordinarily difficult question to which we do not yet have a solution. Various plausible hypotheses have been put forward, e.g., this allows the brain to simulate and explore scenarios or ideas that it could not easily do or that it would potentially be dangerous to do during wakefulness."
3. Scientists have identified three distinct groups of hallucinations.
A 1999 study identified three unique symptoms experienced by sleep paralysis sufferers.
The Sleep Paralysis Project summarized these as:
Intruder: Sensed presence, fear, auditory and visual hallucinations;
Incubus: Pressure on chest, breathing difficulties, pain;
Unusual Bodily Experiences: These may include flying/floating sensations, out of body experiences, and feelings of bliss.
Redditor KingKolon described his terrifying experiences with the "intruder" hallucination:
"I used to have sleep paralysis on a monthly basis. Most of incidents were basically the same. I'd be sleeping on my back. I could see the room, but couldn't move my eyes. Usually dark figures would appear in the peripheral of my vision. The figures would terrify me. I had to scream myself awake. Usually started as a low growl and developed into a scream. My significant other could testify to this. But a few occasions stand out. Once, I had a dark figure whisper into my ear. It was some sort of nursery rhyme. The craziest part of it, is that it was mono. I could only hear it in the ear that was being whispered into."
4. Sleep position may contribute.
In her book, Sleep Paralysis: Night-mares, Nocebos, and the Mind-Body Connection, Professor Shelley Adler writes that "Since lying in a supine position is five times more likely during sleep paralysis than during normal sleep, people hoping to prevent the disorder are advised to avoid sleeping on their backs."
Additionally, a 2004 study conducted by sleep researchers at Turkey's Yuzuncu Yil University found that 40.9 percent of people who slept on their left side suffered nightmares while only 14.9 percent of right-side sleepers suffered the same.
Sleep on your right side.
5. There is also an opposite disorder.
Should the brain fail to induce muscle atonia in a sleeper, they may physically act out their dreams. This is known as rapid eye movement (REM) sleep behavior disorder. Unlike sleep paralysis, this can cause injury to the sleeper (as well as anyone nearby).
6. The "intruder" hallucination is so common that people have given it a name: the Sleep Paralysis Demon.
In a popular Ask Reddit post, BergyBMX posed the question, "Victims of sleep paralysis, what was your run-in with the sleep paralysis demon like?" and gathered more than 4000 comments.
They were all terrifyingly similar.
"I've only experienced it three times but my first time was the worst. I've never had any visual encounters but when it happened the first time I was laying on my left side and started to feel that pressure on my chest. When I realized I was paralyzed and started panicking, something whispered in my ear 'just coming in to say goodnight.' That's when I felt like something was pushing me towards the edge of my bed."
"This is word for word what I experience two-three times a month. Except it's obviously feminine voice telling me, 'Go back to sleep' or, 'Goodnight, baby' and, I can see her face and body.
She's draped in black clothing that seems wet. Skeleton hands but, a very soft, feminine, young face. Eyes like black holes.
She's always sitting on my chest."
"I saw a cat sized shadow creature at the base of my bed and it slowly crawled up on to my sheets and finally upto my chest. I felt uncomfortable"
"A little girl in the corner of my room staring at me. Then, without notice, she shrieks and runs up and starts choking me."
7. You WILL wake up.
Sleep paralysis is terrifying, but it cannot hurt you in and of itself. You will eventually wake up.
"I usually have to start by wiggling a toe, or a finger, and then keep that momentum going until I fully wake. It takes an extreme amount of effort and if I don't keep the effort constant, I have to start all over again."
"I no longer struggle and panic, I just force myself to stay calm and go back to sleep."
— (account deleted)
"I usually have minor motor control of my toes, and am able to break myself out of the paralyzed state by flicking my toes together, which creates enough stimulation to break through the paralysis and wake me up."
Tell us about your experiences with sleep paralysis. How do you wake yourself up? What's the sleep paralysis demon look like to you? Let us know in the comments below.