Sleep paralysis is a condition characterized by temporary paralysis of the body shortly after waking up (known as hypnopompic paralysis) or, less often, shortly before falling asleep (known as hypnagogic paralysis).
Physiologically, it is closely related to the normal paralysis that occurs during REM (rapid eye movement) sleep, also known as REM atonia. Sleep paralysis occurs when the brain is awakened from an REM state into essentially a normal fully awake state, but the bodily paralysis is still occurring. This causes the person to be fully aware, but unable to move. In addition, this state is usually accompanied by hypnagogic hallucinations.
More often than not, sleep paralysis is believed by the person affected by it to be no more than a dream. This is the reason why there are many dream recountings which describe the person lying frozen and unable to move. The hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as simply a dream, as one might see completely fanciful objects in a room alongside the normal vision one can see.
Symptoms
The primary symptom of sleep paralysis is conscious partial or complete skeletal muscle paralysis during the hypnopompic or hypnagogic states. In other words, it is the sense of being aware that one is unable to move or speak while falling asleep or waking up. Sleep paralysis is often accompanied by hypnagogic hallucinations. These hallucinations can be auditory, tactile, and/or visual. If a polysomnography is taken, at least one of the following will be shown: skeletal muscle tone suppression, REM sleep at sleep onset, or dissociated REM sleep. The sleep paralysis persists anywhere from a few seconds to minutes before the person is able to either return to REM sleep or to become fully awake. However, the sense of how much time has gone by is often distorted during sleep paralysis. People who are fortunate enough to be facing a clock while having an episode may often be surprised to see how little time has gone by during an episode that seems to last a long time.
Possible causes
Little is known about the physiology of sleep paralysis. However, some have suggested that it may be linked to post-synaptic inhibition of motor neurons in the pons region of the brain. In particular, low levels of melatonin may stop the depolarization current in the nerves, which prevents the stimulation of the muscles.
There is also a significant positive correlation between those experiencing this disorder frequently and those suffering from narcolepsy. However, various studies suggest that many or most people will experience sleep paralysis at least once or twice in their lives.
Some report that various factors increase the likelihood of both paralysis and hallucinations. These include:
- Sleeping in a supine position (facing upwards)
- Irregular sleeping schedules; naps, sleeping in, sleep deprivation
- Increased stress
- Sudden environmental/lifestyle changes
- A lucid dream that immediately precedes the episode
Cultural references
- In India, there are two thoughts about sleep paralysis. One of the signs of approaching enlightenment is "witnessing sleep," that is to say, being seemingly lucid in sleep — such as with sleep paralysis. It was also believed within the movement that rakshasas (Hindu demons) may assail those making strides towards their own enlightenment and the good of all mankind. The other thought is a female entity, called Mohini (a demoness from the underworld), comes into the night-time world by means of ascending through a deep well. She is enchantingly beautiful, yet simultaneously horrific, unearthly, and deadly. Like her British Isles counterparts, she also seeks a male lover and human genetic material, presumably for the purpose of bearing a hybrid demon/human child.
- In Japan, sleep paralysis is referred to as kanashibari (金縛り, literally: "bound or fastened in metal": kana: metal, shibaru: to bind, tie, fasten")
- In Newfoundland, as a visit from the "old hag" (Ag Rog)
- In Mexico, as subida del muerto (the dead getting on top)
- In Turkish, as karabasan (black buster) and in Hazaragi, as Syahi Zer Kado (pressing ink)
- In the Southern United States, people have described it as "The witch riding your back"
- In Korea, it is referred as Gawinullim, literally in English: "To be pressed by Gawi." The meaning of Gawi is unclear but generally known to mean "spirits" or "demons." Another word in Korean "Gawi" is a homonym that means "scissors", which creates confusion for the accurate meaning of the word.
- In Indonesia, Javanese peoples called it "nindih" (To be seated upon)
- In Philippines, Sleep paralysis is often associated with Bangungot.
- In Vietnam, sleep paralysis is known as "ma đè", meaning a ghost or spirit lying on top of or pressing down on the person.
- In the West Indies, being "ridden by a duppy"
- The common belief in China is that a spirit or ghost is sitting or lying on top of the individual while they were sleeping, causing the sleep paralysis. This is thought to be a minor body possession by the forces from the dead, and usually doesn't cause any harm to the victim.
- In medieval times of Europe, attacks of sufferers of sleep paralysis may have given rise to the belief in mara, incubi, succubi, other demons and witchcraft.
- In traditional Russian belief symptoms reminiscent of sleep paralysis were attributed to the anger of domovoi, the home spirit, punishing people for bad husbandship or betrayal.
- Some scientists believe that many supposed occurrences of alien abduction, out-of-body travel, and other seemingly paranormal events may actually be due to misinterpreting the sensory effects of sleep paralysis.
- Others have argued that sleep paralysis might be the point of separation of the "dream body" from the physical body and out-of-body travel then begins.
Sleep paralysis in literature
There is a particularly fascinating account of sleep paralysis in Herman Melville's novel Moby-Dick. Chapter 4 (The Counterpane) is an account of Ishmael's meditation on an episode of sleep paralysis in the middle of which he could not distinguish the difference between Queequeg's arm and the quilt. Indeed, he could not even distinguish the difference between his own body and his surroundings. He then recalls an earlier episode of sleep paralysis from his childhood, which he determines was the precise moment he discovered the feeling of "otherness" of his own body with respect to his surroundings.
See also
References
- Bower, Bruce (July 9, 2005). "Night of the Crusher." Science News.
- Conesa, J. (2000). Geomagnetic, cross-cultural and occupational faces of sleep paralysis: An ecological perspective. Sleep and Hypnosis, 2, (3), 105-111.
- Conesa, J. (2002). Isolated Sleep Paralysis and Lucid Dreaming: Ten-year longitudinal case study and related dream frequencies, types, and categories. Sleep and Hypnosis, 4, (4), 132-143.
- Conesa, J. (2003). Sleep Paralysis Signaling (SPS) As A Natural Cueing Method for the Generation and Maintenance of Lucid Dreaming. Presented at The 83rd Annual Convention of the Western Psychological Association, May 1 - 4, 2003 in Vancouver, BC, Canada.
- Conesa-Sevilla, Jorge (2004). Wrestling With Ghosts: A Personal and Scientific Account of Sleep Paralysis. Pennsylvania: Xlibris/Randomhouse.
- Firestone K. The “Old Hag”: sleep paralysis in Newfoundland. The Journal of Psychoanalytic Anthropology 1985; 8:47-66.
- Fukuda K, Miyasita A, Inugami M, Ishihara K. High prevalence of isolated sleep paralysis: kanashibari phenomenon in Japan. Sleep 1987; 10:279-286.
- Hartmann E. The nightmare: the psychology and biology of terrifying dreams. New York:Basic,1984.
- Hufford D.J. The terror that comes in the night: an experience-centered study of supernatural assault traditions. Philadelphia:University of Pennsylvania Press, 1982
- Kettlewell, N; Lipscomb, S; Evans, E. (June, 1993). "Differences in neuropsychological correlates between normals and those experiencing "Old Hag Attacks'." Perceptual and Motor Skills. 76 (3 Pt 1): 839-45; discussion 846. PMID 8321596
- Ness RC. “The Old Hag” phenomenon as sleep paralysis: a bicultural interpretation . Culture, Medicine and Psychiatry 1978; 2:15-39.
- Ohayon MM, Zulley J, Guilleminault C, Smirne, S. Prevalence and pathologic associations of sleep paralysis in the general population. Neurology, 1999; 52:1194-1200.
- Sagan, Carl (1997). The Demon-Haunted World: Science as a Candle in the Dark.
- Schneck JM. Sleep paralysis and microsomatognosia with special reference to hypnotherapy . The International Journal of Clinical and Experimental Hypnosis 1977; XXV:72-77.
- Takeuchi T, Miyasita A, Sasaki Y, Inugami M, Fukuda K. Isolated sleep paralysis elicited by sleep interruption. American Sleep Disorders Association and Sleep Research Society, 1992; 15: 217-225.
External links
- How to Cope with Sleep Paralysis
- Sleep Paralysis Information Service
- Susan Blackmore on sleep paralysis
- The Skeptic's Dictionary entry on Sleep Paralysis
- Sleep paralysis at Here Be Dreams
- Sleep information and links from Stanford University
- Sleep Paralysis and Associated Hypnagogic and Hypnopompic Experiences from Waterloo University
- Abduction by Aliens or Sleep Paralysis? - Skeptical Inquirer magazine, May/June 1998