Sleep paralysis is a condition that occurs in that state just before falling to sleep (hypnagogic state) or just before fully awakening from sleep (hypnopompic state). Although the condition may last for only a few seconds, during that time a person undergoing sleep paralysis is unable to move or speak and often experiences a sense of fear that there is some unknown presence in the room. Along with such hallucinations as seeing ghosts, angels, devils, and extraterrestrial beings, many individuals undergoing sleep paralysis also report the sensation of being touched, pulled, or feeling a great pressure on the chest.
A general consensus among researchers links sleep paralysis with rapid eye movement (REM), the dream state. While in the normal state of dreaming, the muscles relax and the brain blocks signals that would permit the limbs to move, thus preventing the body from acting out its dreams. In the case of sleep paralysis, the usual barrier between sleeping and wakefulness temporarily drops and certain sleep phenomena, of which immobility is one, enter into wakefulness. Some individuals, momentarily paralyzed, suffer feelings of dread, helplessness, and become convinced that they have been visited by some supernatural presence.
The 1990 International Classification of Sleep Disorders reports that sleep paralysis may occur to 40 to 60 percent of the population once or twice in a lifetime, but happens quite frequently to people who suffer from narcolepsy, a sleep disorder. Research has also determined that instances of sleep paralysis usually begin around the ages of 16 and 17, increases through the teen years, and generally declines during the 20s. Although the condition is comparatively rare during the 30s, roughly 3 to 6 percent of the general population may continue on occasion to experience sleep paralysis throughout their lives, especially if they undergo sleep deprivation or experience frequent sleep disruption.
Because the experience is extremely frightening for many who suffer from sleep paralysis, they may be reluctant to discuss the problem because they have become convinced that they have witnessed a supernatural visitation or because they fear they are going insane. Researchers insist that while the condition of sleep paralysis may be unpleasant and unsettling, it is not indicative of any serious long-term psychological problem. Those enduring severe sleep paralysis have been successfully treated with certain antidepressants that inhibit REM sleep. Even more effective, many sleep researchers maintain, is to understand more about what the condition is and learn not to fear it.