Hypnopompic Sleep Paralysis, Sleep
Paralysis, Hypnopompic, Sleep, Paralysis, Hypnagogic, narcolepsy
Sleep paralysis is a phenomenon during
which an individual is unable to move during falling asleep or awakening, but
is aware of their surroundings. It is often accompanied by frightening
hallucinations to which one is unable to react because of paralysis and
perceived physical experiences, such as a strong current running through the
upper body. Sleep paralysis poses no immediate risk to those who experience it,
although it occasionally causes significant distress. Episodes last from
several seconds to several minutes.
Genetics and sleep deprivation are a major
cause of sleep paralysis, and it has also been linked to disorders such as
narcolepsy, migraines, stress, anxiety disorders, trauma and obstructive sleep
apnea. Sleeping in a fixed supine position increases the chance of sleep
paralysis. The underlying mechanism is believed to result from disrupted REM
sleep when there should be a general inability to move muscle to prevent the
sleeper from acting out their dreams.
Sleep paralysis is closely related to REM
atonia, the paralysis that occurs as a natural part of REM (rapid eye movement)
sleep. Sleep paralysis occurs either when falling asleep, or when awakening
from sleep. When it occurs upon falling asleep, the person remains aware while
the body shuts down for REM sleep, a condition called hypnagogic or preterminal
sleep paralysis. When it occurs upon awakening, the person becomes aware before
the REM cycle is complete, and it is called hypnopompic or postorbital.
Between 8% and 50% of people experience
sleep paralysis at some point in time.
