People with sleep paralysis are not able to move their body or limbs. It can occur either when falling asleep or waking up. Brief episodes of partial or complete skeletal muscle paralysis can occur during sleep paralysis. Sometimes this sleep disorder runs in families, but the cause of sleep paralysis is not known.
This disorder is not harmful, but people experiencing it often are fearful because they do not know what is happening. An episode of sleep paralysis often is terminated by sound or touch. Within minutes, the person who felt paralyzed is able to move again. It may occur only once in a lifetime or can be a recurrent phenomenon. It is seen most commonly in people with narcolepsy.