[1] Imagined sounds such as humming, hissing, static, zapping and buzzing noises are reported during sleep paralysis.

[7] People also have sensations of being dragged out of bed or of flying, numbness, and feelings of electric tingles or vibrations running through their body.

Under normal conditions, medial and vestibular nuclei, cortical, thalamic, and cerebellar centers coordinate things such as head and eye movement, and orientation in space.

Further studies must be conducted to determine whether there is a mistake in the signaling pathway for arousal as suggested by the first theory presented, or whether the regulation of melatonin or the neural populations themselves have been disrupted.

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

This helplessness can intensify the effects of the threat response well above the level typical of normal dreams, which could explain why such visions during sleep paralysis are so vivid.

[8] A similar process may explain hallucinations, with slight variations, in which an evil presence is perceived by the subject to be attempting to suffocate them, either by pressing heavily on the chest or by strangulation.

[13] These include shallow rapid breathing, hypercapnia, and slight blockage of the airway, which is a symptom prevalent in sleep apnea patients.

[8] According to this account, the subjects attempt to breathe deeply and find themselves unable to do so, creating a sensation of resistance, which the threat-activated vigilance system interprets as an unearthly being sitting on their chest, threatening suffocation.

[18] When ISP episodes are more frequent and cause clinically significant distress or interference, it is classified as "recurrent isolated sleep paralysis" (RISP).

[8] It can be difficult to differentiate between cataplexy brought on by narcolepsy and true sleep paralysis, because the two phenomena are physically indistinguishable.

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.

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.

[4][30] Lifetime prevalence rates derived from 35 aggregated studies indicate that approximately 8% of the general population, 28% of students, and 32% of psychiatric patients experience at least one episode of sleep paralysis at some point in their lives.

[17][10] In surveys from Canada, China, England, Japan and Nigeria, 20% to 60% of individuals reported having experienced sleep paralysis at least once in their lifetime.

[7] In general, non-whites appear to experience sleep paralysis at higher rates than whites, but the magnitude of the difference is rather small.

[32] Such sleep paralysis was widely considered the work of demons, and more specifically incubi, which were thought to sit on the chests of sleepers.

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.

[33] The night hag is a generic name for a folkloric creature found in cultures around the world, and which is used to explain the phenomenon of sleep paralysis.

In Albanian folk beliefs, Mokthi is believed to be a male spirit with a golden fez hat who appears to women who are usually tired or suffering and stops them from moving.

A similar tradition is present in the Sardinian folklore, where the Ammuntadore is known as a creature that mounts on the people's chest during their sleep to give them nightmares, and that can change its shape according to the person's fears.

[51] The Old Hag is well-enough known in the province to be a pop culture figure, appearing in films and plays[52] as well as in crafted objects.

[53] Nigeria[54] has myriad interpretations of the cause of sleep paralysis, due to numerous cultures and belief systems that exist there.

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.

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...

"[57] 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.

It is feeling your bed with its horns-it is boring for [into] you",[58] 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 laboured, exactly as if they were pushing their way through hostile forces.

"[59] 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.

[60] The Nightmare is a 2015 documentary that discusses the causes of sleep paralysis as seen through extensive interviews with participants, and the experiences are re-enacted by professional actors.

In synopsis, it proposes that such cultural phenomena as alien abduction, the near-death experience and shadow people can, in many cases, be attributed to sleep paralysis.