Sleep paralysis is when, during waking up or falling asleep, a person is aware but unable to move or speak.

During an episode, one may hallucinate (hear, feel, or see things that are not there), which often results in fear. Episodes generally last less than a couple of minutes. It may occur as a single episode or be recurrent.

The condition may occur in those who are otherwise healthy or those with narcolepsy, or it may run in families as a result of specific genetic changes. The condition can be triggered by sleep deprivation, psychological stress, or abnormal sleep cycles.

The underlying mechanism is believed to involve a dysfunction in REM sleep. The diagnosis is based on a person’s description. Other conditions that can present similarly include narcolepsy, atonic seizure, and hypokalemic periodic paralysis.

Treatment options for sleep paralysis have been poorly studied. It is recommended that people be reassured that the condition is common and generally not serious. Other efforts that may be tried include sleep hygiene, cognitive behavioral therapy, and antidepressants.

Between 8% and 50% of people experience sleep paralysis at some time. About 5% of people have regular episodes. Males and females are affected equally.

Sleep paralysis has been described throughout history. It is believed to have played a role in the creation of stories about alien abduction and other paranormal events.

Signs and symptoms

The main symptom of sleep paralysis is being unable to move during awakening.

Imagined sounds such as humming, hissing, static, zapping and buzzing noises are reported during sleep paralysis. Other sounds such as voices, whispers, and roars are also experienced.

These symptoms are usually accompanied by intense emotions such as fear and panic. People also have sensations of being dragged out of bed or of flying, numbness, and feelings of electric tingles or vibrations running through their bodies.

Sleep paralysis may include hypnagogic hallucinations, such as a supernatural creature suffocating or terrifying the individual, accompanied by a feeling of pressure on one’s chest and difficulty breathing.

Another example of a hallucination involves a menacing shadowy figure entering one’s room or lurking outside one’s window, while the subject is paralyzed.

Hallucinations

Several types of hallucinations have been linked to sleep paralysis: the belief that there is an intruder in the room, the presence of an incubus, and the sensation of floating.

A neurological hypothesis is that in sleep paralysis the mechanisms which usually coordinate body movement and provide information on body position become activated and, because there is no actual movement, induce a floating sensation.

The intruder and incubus hallucinations highly correlate with one another, and moderately correlated with the third hallucination, vestibular-motor disorientation, also known as out-of-body experiences, which differ from the other two in not involving the threat-activated vigilance system.

Prevention

Several circumstances have been identified that are associated with an increased risk of sleep paralysis. These include insomnia, sleep deprivation, an erratic sleep schedule, stress, and physical fatigue.

It is also believed that there may be a genetic component in the development of RISP, because there is a high concurrent incidence of sleep paralysis in monozygotic twins. Sleeping in the supine position has been found as an especially prominent instigator of sleep paralysis.

Sleeping in the supine position is believed to make the sleeper more vulnerable to episodes of sleep paralysis because in this sleeping position it is possible for the soft palate to collapse and obstruct the airway.

This is a possibility regardless of whether the individual has been diagnosed with sleep apnea or not. There may also be a greater rate of microarousals while sleeping in the supine position because there is a greater amount of pressure being exerted on the lungs by gravity.

While many factors can increase the risk for ISP or RISP, they can be avoided with minor lifestyle changes.

Treatment

Medical treatment starts with education about sleep stages and the inability to move muscles during REM sleep. People should be evaluated for narcolepsy if symptoms persist.

The safest treatment for sleep paralysis is for people to adopt healthier sleeping habits. However, in more serious cases tricyclic antidepressants or selective serotonin reuptake inhibitors (SSRIs) may be used.

Despite the fact that these treatments are prescribed there is currently no drug that has been found to completely interrupt episodes of sleep paralysis a majority of the time.

Cultural significance and priming

Although the core features of sleep paralysis (e.g., atonia, a clear sensorium, and frequent hallucinations) appear to be universal, the ways in which they are experienced vary according to time, place, and culture.

Over 100 terms have been identified for these experiences. Some scientists have proposed sleep paralysis as an explanation for reports of paranormal phenomena such as ghosts, alien visits, demons or demonic possession, alien abduction experiences, the night hag, and shadow people haunting.

The night hag is a generic name for a fantastical creature from the folklore of various peoples which is used to explain the phenomenon of sleep paralysis. A common description is that a person feels the presence of a supernatural malevolent being which immobilizes the person as if sitting on the chest.

Various cultures have various names for this phenomenon or supernatural character. For example, sleep paralysis is referred to as a pandafeche attack in Italy. Among Italians, the pandafeche may refer to an evil witch, sometimes a ghostlike spirit or a terrifying catlike creature.

Sleep paralysis among Cambodians is known as “the ghost pushes you down,” and entails the belief in dangerous visitations from deceased relatives. In Egypt, sleep paralysis is conceptualized as a terrifying jinn attack. The jinn may even kill its victims. Sleep paralysis is sometimes interpreted as space alien abduction in the United States.

According to some scientists, culture may be a major factor in shaping sleep paralysis. When sleep paralysis is interpreted through a particular cultural filter, it may take on greater salience.

For example, if sleep paralysis is feared in a certain culture, this fear could lead to conditioned fear, and thus worsen the experience, in turn leading to higher rates.

Consistent with this idea, high rates and long durations of immobility during sleep paralysis have been found in Egypt, where there are elaborate beliefs about sleep paralysis, involving malevolent spirit-like creatures, the jinn.

Research has found that sleep paralysis is associated with great fear and fear of impending death in 50% of sufferers in Egypt. A study comparing rates and characteristics of sleep paralysis in Egypt and Denmark found that the phenomenon is three times more common in Egypt versus Denmark.

In Denmark, unlike Egypt, there are no elaborate supernatural beliefs about sleep paralysis, and the experience is often interpreted as an odd physiological event, with overall shorter sleep paralysis episodes and fewer people (17%) fearing that they could die from it.

Literature

Various forms of magic and spiritual possession were also advanced as causes in literature. In nineteenth-century Europe, the vagaries of the diet were thought to be responsible.

For example, in Charles Dickens’s A Christmas Carol, Ebenezer Scrooge attributes the ghost he sees to “… an undigested bit of beef, a blot of mustard, a crumb of cheese, a fragment of an underdone potato…” In a similar vein, the Household Cyclopedia (1881) offers the following advice about nightmares:

“Great attention is to be paid to regularity and choice of diet. Intemperance of every kind is hurtful, but nothing is more productive of this disease than drinking bad wine. Of eatables, those which are most prejudicial are all fat and greasy meats and pastry… Moderate exercise contributes in a superior degree to promote the digestion of food and prevent flatulence; those, however, who are necessarily confined to a sedentary occupation, should particularly avoid applying themselves to study or bodily labor immediately after eating… Going to bed before the usual hour is a frequent cause of night-mare, as it either occasions the patient to sleep too long or to lie long awake in the night. Passing a whole night or part of a night without rest likewise gives birth to the disease, as it occasions the patient, on the succeeding night, to sleep too soundly. Indulging in sleep too late in the morning is an almost certain method to bring on the paroxysm, and the more frequently it returns, the greater strength it acquires; the propensity to sleep at this time is almost irresistible.”

J. M. Barrie, the author of the Peter Pan stories, may have had sleep paralysis. He said of himself ‘In my early boyhood it was a sheet that tried to choke me in the night.’ He also described several incidents in the Peter Pan stories that indicate that he was familiar with an awareness of a loss of muscle tone whilst in a dream-like state.

For example, Maimie is asleep but calls out ‘What was that…It is coming nearer! It is feeling your bed with its horns-it is boring for [into] you’, and when the Darling children were dreaming of flying, Barrie says ‘Nothing horrid was visible in the air, yet their progress had become slow and labored, exactly as if they were pushing their way through hostile forces. Sometimes they hung in the air until Peter had beaten on it with his fists.

Barrie describes many parasomnias and neurological symptoms in his books and uses them to explore the nature of consciousness from an experiential point of view.

*This article uses material from the Wikipedia article Sleep paralysis, which is released under the Creative Commons Attribution-ShareAlike License 3.0 (view authors).