Sleep paralysis causes a temporary inability to move your body, though you are full conscious of your surroundings. Though this can be a terrifying experience, it is somewhat common and generally harmless. Episodes of sleep paralysis often last only a few seconds, though cases have been reported of symptoms lasting a minute or more. A major concern for many people who have experienced sleep paralysis is “can sleep paralysis cause death?” While the experience is often unpleasant, there is little to no danger involved in sleep paralysis.

What causes sleep paralysis is a subject that there has been many studies on. Most results suggest that it may be caused by a slight change in the normal human sleep pattern. For most people, there are four stages of sleep before entering rapid eye movement, or REM, sleep. REM sleep is the stage in your sleep pattern in which dreaming occurs. The average person will have multiple complete sleep cycles in a typical evening’s rest. However, it has been found that when the first stages of non-REM sleep are skipped, and the person goes straight to a REM sleep state, sleep paralysis is more likely to occur.

During REM sleep, the brain sends signals to the body to prevent muscle movement. It is thought that this prevents you from acting out any actions you experience while dreaming. When the normal sleep cycle is interrupted, these signals can be interrupted as well. This results in being fully conscious momentarily, but being unable to move your extremities. While not as common as the basic episode of sleep paralysis, sometimes sleep paralysis causes hallucinations. These often include feelings of falling, flying, suffocating or vibrating. Visual and auditory hallucinations can also occur. These vary widely, however, the hallucinations often involve seeing dark bodies, hearing odd noises or voices, or sensing the presence of something in the room. It is thought this is the product of still experiencing the effects of REM sleep while in a conscious state.

According to Scientific American, 20 to 60 percent of people in different countries report experiencing sleep paralysis at least once. Of these people, 5 percent report auditory, visual, or physical hallucinations or symptoms. The chances of experiencing sleep paralysis increases in people suffering from narcolepsy, though all sleep paralysis causes are not fully understood.

Cases of sleep paralysis are not specific to any one region or country of the world. Common names for sleep paralysis include the Japanese “kanashibari,” the Chinese “gui ya,” and the “kokma” of the West Indies. All of these names are derived from folklore involving spirits or otherworldly beings assaulting the victim. This may be due to the feelings of suffocation and chest tightness that sleep paralysis causes. Many people also attribute possible ghost sitings, abductions, and out-of-body experiences to sleep paralysis. Scientifically, there is no evidence to prove or disprove this correlation.