Sleep paralysis, or atonia, is a temporary inability to move while dreaming. Atonia is a safety measure that prevents us from acting out our dreams. In some cases, however, sleep paralysis occurs as people fall asleep and wake up. In this frightening experience the affected person cannot move or speak for several seconds.
An estimated 20 to 25 percent of the population has experienced some degree of sleep paralysis. Extreme cases can occur nightly for years. The condition often begins during the teen years, but can start at any time.
Being unable to move is scary enough, but many cases of sleep paralysis are accompanied by dreamlike hallucinations. Called hypnagogic hallucinations, these dreamlike sensations are often frightening and make people feel threatened. Many people report feeling an evil "presence" that watches them intently. The combination of sleep paralysis and hypnagogic hallucinations is a common symptom of narcolepsy.
Occasionally, people report that their hallucinations turn violent during paralysis. People report feeling a crushing weight on their chests, a condition called the incubus (from the Latin incubare, meaning "to press upon"). People may even believe they are being strangled or attacked by the incubus. The incubus hallucinations are responsible for many myths, including that of a hag who sits on sleepers, crushing them.
Alien Abductions and Out of Body Experiences (OOBE)
Just as the incubus is the base of older myths, hypnagogic hallucinations may be responsible for claims of out of body experiences (OOBE) or alien abductions. Hallucinations during atonia can produce sounds, and sensations are well as visions. Some people report "floating," suggesting that out of body experiences may be undiagnosed sleep paralysis.
In addition to OOBE reports, reported alien abductions might result from the feeling of a "presence" watching the paralyzed person. Couple this sensation with the incubus, and many "alien abductions" can be explained.
Waiting it out is best way to deal with sleep paralysis. People often report pain if they attempt to move their limbs. Once the episode is over, bodily control returns quickly, although the uneasiness and fear associated with an episode may last longer. People who are aware that they are experiencing hallucinations often recover from episodes faster.