Sleep paralysis is a frightening phenomenon in which a person awakens from sleep but feels completely paralyzed, unable to move or speak. The experience is usually accompanied by extreme fear and terrifying hallucinations, which may be visual, tactile and/or auditory. Many sufferers have reported feeling as if an evil presence was in the room.

Sleep paralysis typically occurs during a transitional stage of sleep, most often while waking up, but occasionally while falling asleep. The experience can last from a few seconds to several minutes.

One hypothesis is that sleep paralysis is linked to a disruption in REM (rapid eye movement) sleep. REM occurs along with muscle atonia, a state of complete muscle relaxation or paralysis. This lack of muscle control is meant to prevent people from acting out their dreams.

In this hypothesis, the sleeping person becomes conscious before the brain signals the body to move again. This may lead to terror and other negative emotions, prompting scary dream-like hallucinations.

Sleep paralysis is a common condition with up to four in ten people experiencing it at least once in their lifetime. Individuals at greatest risk for sleep paralysis are the sleep-deprived, those under extreme stress or those who overuse stimulants. People who practice lucid dreaming techniques are also more likely to experience sleep paralysis.

The condition most often occurs in people who are sleeping on their backs. Adjusting the body to sleep in other positions, such as on the side or the stomach, appears to decrease the risk for sleep paralysis.

Example: After experiencing a frightening episode of sleep paralysis in which she woke up and couldn’t move or speak, Kara has begun practicing meditation to lower her stress levels and started sleeping on her side at night.