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What is Sleep Paralysis?

Sleep paralysis is a disorder in which you are unable to move or speak just before you are about to fall asleep or just as you are waking up. It is not dangerous, and usually lasts for a few seconds to a few minutes. If it happens when you are falling asleep, it is called hypnagogic sleep paralysis. It's known as hypnopompic sleep paralysis if it occurs as you are waking up.

Sleep paralysis is common. Surveys from different countries show that between one fifth and three fifths of adults have experienced sleep paralysis at least once in their lives. This condition sometimes runs in families. While sleep paralysis can happen at any time of life, most people experience their first episode during their teenage years. It affects both sexes equally.

Sleep paralysis is often associated with narcolepsy, a medical condition in which the sufferer has uncontrollable sleep attacks during the day. However, many people who experience sleep paralysis do not have narcolepsy.

Symptoms of Sleep Paralysis

When you experience an episode of sleep paralysis, in addition to being unable to move or speak, you may feel extremely frightened. You may have auditory or visual hallucinations or feel as though you are floating above the bed. You may sense, or even see, a threatening person or creature watching you. You may feel as though someone is strangling you or as if someone is sitting on you or crushing your chest, suffocating you.

Sleep paralysis can feel like you are being pinned down

Myths and Legends about Sleep Paralysis

Many stories, which can be found in cultures throughout the world,  blame the symptoms of sleep paralysis on an attack by a witch, demon or other supernatural creature.  The term "hag-riding" has been used to describe the feeling of being crushed on the bed, allegedly by a witch, or hag.

More recently, researchers have come to believe that people who claim to have been abducted by aliens were, in fact, experiencing sleep paralysis.

What Causes Sleep Paralysis and Its Symptoms?

Sleep paralysis happens as you are moving into or out of rapid eye movement (REM) sleep, the stage of sleep in which you are most likely to dream. During REM sleep, the large voluntary muscles in your body become paralyzed, probably to prevent you from injuring yourself while dreaming. When you have an episode of sleep paralysis, you are conscious but you are experiencing the paralysis associated with REM sleep.

Some people refer to sleep paralysis as "awareness during sleep paralysis" (ASP), to distinguish it from the normal paralysis that occurs when you are asleep and dreaming.

During REM sleep, your breathing becomes shallow and rapid. The muscle tone in your upper airways decreases, and your airways become partly blocked. During an episode of sleep paralysis, you may have the feeling that you are not getting enough air and try to breathe more deeply. However, if you try to use your chest muscles to help aid your breathing, you will find that you can't move them. You will feel as though your efforts are being resisted, and you might interpret this as someone crushing your chest. You may interpret the feeling of constriction in your airways as choking. If you start to panic, you might struggle to overcome the paralysis. This can cause you to experience muscle spasms and feel pain. Your brain may then interpret this as someone physically assaulting you.

Neuroscientists believe that the feeling of intense terror that often accompanies sleep paralysis is caused by activity in the amygdala. The amygdala is the part of the brain that processes emotions. It is responsible for the "fight or flight" reaction and for conditioning us to be afraid of things.

What Makes You Susceptible to Sleep Paralysis

Sleep paralysis is most likely to occur if your normal sleep patterns are disrupted, for example if you are experiencing jet lag, are working unusual shifts or have been suffering from insomnia.

Sleep paralysis is often associated with stress and with a history of panic attacks. One research study showed that 35% of subjects who had experienced sleep paralysis had also experienced panic attacks when they were awake.

Sleep paralysis is more likely to occur when you are sleeping on your back.

Treatment for Sleep Paralysis

Since sleep paralysis is not harmful, and struggling can just cause you to feel worse, it is probably best to relax and wait for the episode to pass. You might try to move your eyes or a finger or toe.

Some people have found that if they allow themselves to relax during a period of sleep paralysis, they can induce an out of body experience.

Getting enough sleep and trying to reduce stress can help prevent sleep paralysis. You can also avoid sleeping on your back.

If you experience episodes of sleep paralysis frequently, you may be prescribed medicine as a cure.

Sleep Paralysis and Paralysis in Prey Animals

Some scientists have noted a similarity between sleep paralysis and a form of paralysis that occurs in prey animals. When a predator seizes a prey animal, the prey animal may fight for a short while, but it will soon become paralyzed, in a condition known as tonic immobility. Sometimes placing a prey animal on its back will cause it to experience tonic immobility. When it is in this state, the prey animal appears to be dead. This may cause the predator to let its victim go.

Tonic immobility does not happen voluntarily - it is not the same as "playing dead." It is an involuntary reaction to extreme fear in a desperate situation.

The intense fear that people often experience when they suffer from sleep paralysis might resembles the fear that is experienced by an animal that has been stalked and captured. The "evil presence" that you sense during an episode of sleep paralysis might be compared to a predator who wants to destroy you.

Some scientists believe that when you have an episode of sleep paralysis, lying on your back unable to move and possibly feeling like you are being crushed or choked, you unconsciously associate this experience with being attacked by a predator. This is what causes you to believe that you are in the presence of an evil being that is watching you and planning your destruction.