Sleep Paralysis: You're Awake, But You Can't Move

The cause of sleep paralysis isn't known. But it appears likely that many instances of sleep paralysis occur because of difficulty transitioning between different sleep stages, particularly moving in and out of REM sleep.
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Have you ever suffered an episode of sleep paralysis? It can be a tremendously frightening experience, one you're not likely to forget. You wake from sleep immobilized, unable to move your body or turn your head. You try to make a sound, but you can't open your mouth. You feel short of breath, with a strong feeling of pressure on your chest, weighing your body down. You feel a deep sense of dread or danger -- maybe you even feel there's a strange presence in the room.

As frightening as it is, sleep paralysis -- one form of parasomnia -- isn't actually dangerous, nor is it typically a sign of a serious condition. Sleep paralysis is one symptom of narcolepsy, but many instances of sleep paralysis aren't an indication of narcolepsy or another sleep disorder. Episodes of sleep paralysis can last for a few seconds or as long as a few minutes. Sleep paralysis can occur when you are awakened from sleep, and it also can occur when you're in the process of falling asleep. What's behind this difficult sleep experience? The cause of sleep paralysis isn't known. But it appears likely that many instances of sleep paralysis occur because of difficulty transitioning between different sleep stages, particularly moving in and out of REM sleep.

During REM, the body goes into a state of paralysis known as REM atonia. This is a normal part of the sleep stage, when major muscle groups and most voluntary muscles are paralyzed. One important function of this paralysis may be to protect the body from injury during sleep. REM is a sleep stage when much active dreaming occurs. Without the paralyzing effects of REM atonia, we might act out physically in response to our dreams. In certain sleep disorders, including REM Behavior Disorder, the normal paralysis of REM sleep doesn't work as it should, and people act out physically -- sometimes aggressively and violently -- in sleep.

Sleep scientists believe that sleep paralysis may occur when the transitions in and out of REM sleep and other sleep stages don't go smoothly. The paralysis that is typically confined to REM sleep spills over to other sleep stages -- and if you wake, you become aware of your body's paralysis, and the frightening feeling of being unable to move or to speak. Sleep paralysis may also include hallucinations. People often describe feeling a ghost-like presence in the room with them, as well as feelings of terror and foreboding. These hallucinations can include strange sounds and even smells, along with sensations of falling or flying. Although the mechanisms of breathing aren't impaired by sleep paralysis, people sometimes feel breathless, and often feel a weighty pressure on the chest. The experience of sleep paralysis can be terrifying, especially the first time it occurs.

If you've ever experienced sleep paralysis, you're not alone. The phenomenon is actually relatively common, and can occur at any point in life. Estimates vary widely, but as many as 65 percent of people may suffer an episode of sleep paralysis at some point in their lives. Sometimes the phenomenon occurs only once or twice in a person's life, while other people may have more frequent and regular encounters with sleep paralysis. Certain people are more at risk for this frightening sleep disturbance. People with disrupted sleep cycles, people who've experienced trauma, or who suffer from anxiety or depression may be more likely to suffer episodes of sleep paralysis.

New research investigates possible factors that contribute to sleep paralysis -- and the results indicate that genetics may play a significant role. Scientists in the United Kingdom examined the role of heredity in sleep paralysis among a group of 862 twins and siblings. The participants were young adults between the ages 22 and 32, all of whom were enrolled in the Genesis 12-19 study, a long-term, ongoing U.K.-based investigation of genetics and development.

To pinpoint the role that heredity might play, researchers compared data on sleep and the incidence of sleep paralysis for identical twins to data involving non-identical twins and siblings. Identical twins carry almost exactly the same DNA, while non-identical twins and siblings have roughly 50 percent of DNA in common. Their analysis found that genetics was a factor in 53 percent of cases of sleep paralysis among their subjects.

Researchers examined this genetic link more closely by looking at variants of a gene that is involved in control of circadian rhythms, the 24-hour biological rhythms that help to govern sleep-wake cycles. They discovered that people with certain variations of the PER2 gene were more likely to have experienced sleep paralysis. The study also found people with disrupted sleep, as well as people who experienced anxiety, stressful or traumatic events were more likely to suffer episodes of sleep paralysis.

These findings align with previous research suggesting family links to sleep paralysis, as well as to research indicating stress, trauma, anxiety and depression make sleep paralysis more likely. This latest study gives new direction to explore more closely the connection between sleep paralysis and the genes that drive circadian rhythms.

You can help decrease your chances of experiencing sleep paralysis by focusing on the fundamentals of healthy sleep: maintaining a regular sleep routine, avoiding stimulants (especially alcohol), exercising regularly, eating well and avoiding eating late at night. It's also important to tend carefully to stress and to your mental health. Anxiety and depression are common. Seeking treatment for these conditions can help you sleep better overall, and may help you avoid sleep paralysis.

If you do experience sleep paralysis, don't panic. Remind yourself that however frightening and disconcerting, this is a temporary and harmless condition that will soon pass. Understanding what's happening to you physiologically can help you avoid the worst of the fear associated with this scary sleep phenomenon.

Sweet Dreams,

Michael J. Breus, PhD
The Sleep Doctor™