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Imagine this:

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You're fast asleep

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when all of a sudden you're awoken!

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And not by your alarm clock.

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Your eyes open,

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and there's a demon sitting on your chest,

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pinning you down.

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You try to open your mouth and scream,

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but no sound comes out.

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You try to get up and run away,

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but you realize that you
are completely immobilized.

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The demon is trying to suffocate you,

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but you can't fight back.

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You've awoken into your dream,

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and it's a nightmare.

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It sounds like a Stephen King movie,

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but it's actually a medical condition

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called sleep paralysis,

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and about half of the population

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has experienced this strange phenomenon

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at least once in their life.

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This panic-inducing episode

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of coming face-to-face with the creatures

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from your nightmares

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can last anywhere from seconds to minutes

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and may involve visual
or auditory hallucinations

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of an evil spirit

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or an out-of-body feeling
like you're floating.

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Some have even mistaken sleep paralysis

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for an encounter with a ghost

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or an alien abduction.

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In 1867, Dr. Silas Weir Mitchell

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was the first medical professional

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to study sleep paralysis.

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"The subject awakes to consciousness

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of his environment

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but is incapable of moving a muscle.

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Lying to all appearance, still asleep.

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He's really engaged
for a struggle for movement,

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fraught with acute mental distress.

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Could he but manage to stir,

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the spell would vanish instantly."

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Even though Dr. Mitchell was the first

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to observe patients in a state
of sleep paralysis,

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it's so common that nearly every culture

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throughout time has had some kind

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of paranormal explanation for it.

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In medieval Europe, you might
think that an incubus,

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a sex-hungry demon in male form,

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visited you in the night.

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In Scandinavia, the mare,

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a damned woman,

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is responsible for visiting sleepers

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and sitting on their rib cages.

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In Turkey, a jinn holds you down

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and tries to strangle you.

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In Thailand, Phi Am bruises
you while you sleep.

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In the southern United States,

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the hag comes for you.

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In Mexico, you could blame

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subirse el muerto,
the dead person, on you.

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In Greece, Mora sits upon your chest

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and tries to asphyxiate you.

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In Nepal, Khyaak the ghost

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resides under the staircase.

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It may be easier to blame

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sleep paralysis on evil spirits

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because what's actually
happening in your brain

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is much harder to explain.

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Modern scientists believe
that sleep paralysis

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is caused by an abnormal overlap

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of the REM, rapid eye movement,

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and waking stages of sleep.

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During a normal REM cycle,

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you're experiencing
a number of sensory stimuli

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in the form of a dream,

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and your brain is unconscious
and fully asleep.

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During your dream,

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special neurotransmitters are released,

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which paralyze almost all of your muscles.

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That's called REM atonia.

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It's what keeps you
from running in your bed

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when you're being chased in your dreams.

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During an episode of sleep paralysis,

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you're experiencing
normal components of REM.

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You're dreaming and your muscles
are paralyzed,

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only your brain is conscious
and wide awake.

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This is what causes you to imagine

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that you're having an encounter

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with a menacing presence.

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So this explains the hallucinations,

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but what about the feelings of panic,

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strangling,

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choking,

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chest pressure

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that so many people describe?

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Well during REM,

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the function that keeps you

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from acting out your dreams,

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REM atonia,

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also removes voluntary control

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of your breathing.

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Your breath becomes more shallow

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and rapid.

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You take in more carbon dioxide

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and experience a small
blockage of your airway.

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During a sleep paralysis episode,

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a combination of your body's fear response

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to a perceived attack by an evil creature

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and your brain being wide awake

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while your body is in an REM sleep state

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triggers a response for you
to take in more oxygen.

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That makes you gasp

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for air,

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but you can't

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because REM atonia

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has removed control of your breath.

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This struggle for air
while your body sleeps

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creates a perceived sensation

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of pressure on the chest

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or suffocation.

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While a few people experience

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sleep paralysis regularly

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and it may be linked to sleep disorders

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such as narcolepsy,

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many who experience
an episode of sleep paralysis

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do so infrequently,

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perhaps only once in a lifetime.

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So you can rest easy,

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knowing that an evil entity is not trying

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to haunt,

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possess,

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strangle,

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or suffocate you.

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Save that for the horror films!