While I would not want to tottally dismiss the existence of Ghost or better rightly put Familair Spirit. Most people are oblivious of the medical phenomen know as Sleep Paralysis.
Symptoms
The primary symptom of sleep paralysis is 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 may also be accompanied by hypnagogic hallucinations.[1] 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 a few minutes [1] before the person is able to either return to REM sleep or to become fully awake.
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Possible causes
Sleep paralysis occurs during REM sleep in order to prevent the body from manifesting the sleeper's dreams. 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, to prevent the body from enacting the dreamt activity (ie. preventing a sleeper from running when dreaming about running.)
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: [2]
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. Also conscious induction of sleep paralysis is a common technique to enter a state of lucid dreams.
Artificial sleeping aids or antihistamines
Many cultures have different names and explanations for it.
In Chinese folk culture, sleep paralysis is referred as "gǔi yà chúang" (鬼压床), literally: "Ghost press bed": 鬼: ghost, 压: press, 床: bed. The belief 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 India, there are two thoughts about sleep paralysis. One of the signs of approaching enlightenment is "witnessing sleep," that is to say, being 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" (Irish: Ag Rog)
In Mexico, as subida del muerto (the dead climbing on top)
In Greek, as mora (in Greek: μώρα), the name cames has a Slavic root.
In Turkish, as karabasan (black buster)
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, (가위눌림) 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 "tindhihen" (To be seated upon)
In the 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"
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. People in England believed that witches or hags rode on men's chests as they slept, and the feeling of being unable to breathe was attributed to a hag. This is why people who have had very little sleep may be described as looking "hag-ridden".
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.
According to traditional Hmong beliefs, various states of sleep paralysis are thought to be the processes in which an evil spirit or demon sits down on a person usually in retaliation to wrongdoings. Some Hmong have deemed it as the process of getting 'squashed'.
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.
Traditional Islamic cultures would usually interpret this as an encounter with a Jinn (or "djinn"); a race of beings, similar to humans which inhabit the earth. The word "jinn" literally means anything which has the connotation of concealment, invisibility, seclusion and remoteness, and is one of the two beings (the other being Human) addressed directly in the Quran. In Islamic text, and scholarship, Jinns are considered beings, which like humans are accountable for their deeds and thus have free will. They are considered to have life and death, society, culture and religion
You can use the wikipaedia link below to find out more about it,
http://en.wikipedia.org/wiki/Sleep_paralysisSo develop proper sleeping habits and positions. Ok?