In sleep paralysis one feels like he is awake but unable to move. One may feel afraid but cannot call for help. It occurs when a person passes between stages of wakefulness and sleep. Sleep paralysis may leave feeling frightened, if one 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. In most cases, sleep paralysis is simply a sign that your body is not moving smoothly through the stages of sleep. Very rarely sleep paralysis linked to deep underlying psychiatric problems. During the time of these transitions, one 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 usually occurs at one of two times. If it occurs while you are falling asleep, it's called hypnagogic or pre-dormital sleep paralysis. If it happens as you are waking up, it's called hypnopompic or post-dormital sleep paralysis. During sleep, 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.
Last date updated on July, 2014