Sleep Disorders Health Center
Sleep Paralysis
Have you ever felt like you were awake but unable to move? You might have even felt afraid but could not call for help? This condition is called sleep paralysis. Sleep paralysis may leave you feeling frightened, especially if you also see or hear things that aren't really there. Sleep paralysis may happen only once, or you may have it frequently -- even several times a night.
The good news: sleep paralysis is not considered a dangerous health problem. Read on to find out more about sleep paralysis, its possible causes, and its treatment.
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Is Sleep Paralysis a Symptom of a Serious Problem?
Sleep researchers conclude that, in most cases, sleep paralysis is simply a sign that your body is not moving smoothly through the stages of sleep. Rarely is sleep paralysis linked to deep underlying psychiatric problems.
Over the centuries, symptoms of sleep paralysis have been described in many ways and often attributed to an "evil" presence: unseen night demons in ancient times, the old hag in Shakespeare's Romeo and Juliet, and alien abductors. Almost every culture throughout history has had stories of shadowy evil creatures that terrify helpless humans at night. People have long sought explanations for this mysterious sleep-time paralysis and the accompanying feelings of terror.
What Is Sleep Paralysis?
Sleep paralysis is a feeling of being conscious but unable to move. It occurs when a person passes between stages of wakefulness and sleep. During these transitions, you may be unable to move or speak for a few seconds up to a few minutes. Some people may also feel pressure or a sense of choking. Sleep paralysis may accompany other sleep disorders such as narcolepsy. Narcolepsy is an overpowering need to sleep caused by a problem with the brain's ability to regulate sleep.
When Does Sleep Paralysis Usually Occur?
Sleep paralysis usually occurs at one of two times. If it occurs while you are falling asleep, it's called hypnagogic or predormital sleep paralysis. If it happens as you are waking up, it's called hypnopompic or postdormital sleep paralysis.
What Happens With Hypnagogic Sleep Paralysis?
As you fall asleep, your body slowly relaxes. Usually you become less aware, so you do not notice the change. However, if you remain or become aware while falling asleep, you may notice that you cannot move or speak.
What Happens With Hypnopompic Sleep Paralysis?
During sleep, your body alternates between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep. One cycle of REM and NREM sleep lasts about 90 minutes. NREM sleep occurs first and takes up to 75% of your overall sleep time. During NREM sleep, your body relaxes and restores itself. At the end of NREM, your sleep shifts to REM. Your eyes move quickly and dreams occur, but the rest of your body remains very relaxed. Your muscles are "turned off" during REM sleep. If you become aware before the REM cycle has finished, you may notice that you cannot move or speak.
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