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Sleep Paralysis

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You're drifting lazily through hazy dreams when you abruptly become aware of your surroundings. Annoyed that your nocturnal sojourns are coming to an end, you roll onto your side – only it doesn't happen because you are suddenly, inexplicably, unable to move. You may sense an evil presence in the room, perhaps something heavy upon your chest or hands around your neck. As panic mounts you attempt to cry out for help, only that doesn't work either because you are also unable to speak.

Ever experienced this? It's called sleep paralysis, and it's perfectly natural.

What is Sleep Paralysis?

Sleep paralysis (SP) refers to the condition in which a person, usually lying on his back (in a supine position), is about to fall asleep or has just awoken to find himself incapable of movement or speech. It may last anywhere between several seconds and several minutes, during which time the individual may experience mounting fear and panic as well as various forms of sensory hallucination that may be either fantastical or horrific.

The Symptoms of Sleep Paralysis

Sleep paralysis is characterised by inability to move the body or limbs at the onset of sleep or upon awakening, brief episodes of partial or complete skeletal paralysis, and very often episodes of hallucinations, known as hypnagogic and hypnopompic experiences (HHE). It is frequently accompanied by panic, heightened by the inability to speak or cry out. A polysomnograph (sleep recording) will also demonstrate the suppression of skeletal muscle tone, a sleep onset Rapid Eye Movement or 'REM' period and dissociated REM sleep.

All too often the hallucinations manifest in the form of an evil presence nearby, which may be engaged in the relatively benign activity of keenly observing the sleeper - or they may become malevolent and attack the individual. Various other forms of hallucinations may also be encountered, including exosomatic (waves, vibrations and tremors), acoustic (high-pitched ringing, loud or irritating noises), visual (blobs of light, perception of extreme detail in objects), somatosensory (the feeling of one's body being twisted, rotated or compressed, or the sensation of flying or floating), dissociative (out-of-body experiences) and physical (sudden pain in parts of the body) hallucinations1. In some cases, extreme effort to move parts of the body may result in phantom movement whereby the individual feels as though the body part involved were indeed moving even though visual confirmation reveals the contrary. These hallucinations range in intensity from fleeting illusion to full-blown, true hallucination (prior knowledge of this condition tends to soften the blow). However, so vivid are some of these barrages of sensory hallucination that even after the paralysis wears off, the individual is left with a lingering anxiety or dread – especially if that person has never before heard of sleep paralysis – an individual may feel that their sanity is hanging by a thread.

A Short History

'[Those] taken with this disease, imagine that a man of monstrous stature sitteth on them, which with his hands violently stoppeth their mouth, that they can by no meanes cry out, and they strive with their armes and hands to drive him away, but all in vain.'
– Ludwig Lavater, 16th-Century Swiss minister.

There are numerous documentations of sleep paralysis and associated hallucinations throughout history. In the East, descriptions of these conditions date as far back as 400 BC, accounted in a Chinese book of dreams. The famous Greek physician Galen attempted to study the cause of nightmares; both the Greek historian Herodotus and the Roman poet Horace chronicled appearances of the evil entities associated with this condition. Similarly, the word 'nightmare' was originally conceived in the West to describe sleep paralysis. The word 'mare' from the Anglo-Saxon word 'merran', meaning 'to crush', dates back to old English belief that witches or other supernatural beings were responsible for the chest-crushing sensations experienced in sleep paralysis. The term has since transformed into 'nightmare' (the crusher in the night), which we have now come to associate with horrific dreams of monsters and mishap.

Although most of these documentations attribute sleep paralysis to supernatural phenomena, several key figures have attempted to explain it logically. Galen thought the condition was caused by gastric disturbances. Even in the age of religious superstition, 16th Century Swiss minister Ludwig Lavater asserted that, 'physicians do affirme, that these are nothing else but a disease', an opinion that (strangely enough) both the enthusiastic witch-hunter James I and the Elizabethan sceptic Reginald Scot agreed upon. Samuel Wesley chose to remain neutral on the subject, claiming that the experiences could have a natural or supernatural cause depending on particular personal circumstances. Ernest Jones, a Freud pupil, was convinced repressed sexuality was to blame.

And then came the invention and development of electroencephalography in the 1950s, which paved the way for research on sleep patterns and, coupled with the anthropological work of researchers such as Robert Ness and David J Hufford, opened up a new understanding of what we now know to be a neurological glitch.

Sleep Paralysis and the Mechanics of REM

Normal mammalian sleep consists of two states2 of brain activity, non-REM (NREM) sleep and REM sleep, which alternate through the period of slumber in 90 to 120-minute, to 10-minute cycles (the first cycle is about 100 minutes, but grows longer each time around as the respective REM stage extends). Whilst the NREM state is in progress, the body is capable not only of tossing and turning in bed, but also motor events such as sleepwalking and sleep-talking, and the rate of heartbeat and breathing are uniform. However, during REM state, breathing and cardiac-muscle contraction becomes irregular, and the eyes flicker as the individual dreams. In this state the brain locks down muscles in the body (although peripheral muscles are still capable of twitching) by signalling the inhibition of muscular contraction, most likely for protective reasons: acting out a dream can be detrimental, not only to the unfortunate bedmate, but to the sleeper himself3.

However well-maintained, the nervous and endocrine systems responsible for sending out these inhibitor signals will sometimes erringly continue to do so when a person awakes directly from REM sleep or is about to enter wakefully into the state. When this happens, the individual experiences sleep paralysis - as demonstrated in a series of experiments by Kzuhiko Fukuda of Fukushima University involving individuals with high incidence of sleep paralysis; people who were abruptly roused from slumber displayed electrical responses typical of REM sleep even though the brain was awake.

As for the hallucinations accompanying sleep paralysis, those too are the result of brain activity. It has already been demonstrated, by the Canadian neurologist Wilder Penfield in the 1960s, that electrical stimulation of the temporal lobe of the brain induces auditory hallucinations in the wake state. Indeed, it is activity in this temporal lobe that brings about the hallucination of hearing annoying sounds, just as it is the visual cortex to fault for generating internal visual stimuli which manifests in the individual's mind as the often malevolent 'evil' presence watching over them.

Hallucinations and Sleep Paralysis

But how are hallucinations connected to sleep paralysis? As most of us will attest, dreams do not necessarily end when we awaken, but we sometimes continue to drift in a half-waking half-dreaming state of delirium. It is possible that, just as the nervous and endocrine systems4 continue transmitting inhibitor signals to our muscles, the same systems may also keep sending out signals that stimulate dreaming, thus causing an individual who has just woken up to continue experiencing images and sounds in his mind. Indeed it has been speculated by Hishikawa and Shimizu that sleeping paralysis is produced by the over-activation of the neural populations governing the Sleep-on state or (more likely) under-activation of those governing the Sleep-off state – a hypothesis supported by the fact that this condition may be alleviated by serotonin5 and adrenergic6 reuptake inhibitors. Also, unlike normal dreaming, the hallucinations experienced during sleep paralysis are caused by the sensory cortex receiving information generated both inside and outside the individual; the absence of peripheral feedback in response to this gives the hallucination a sense of unreality and bizarreness.

There exists a three-factor structural model of hallucinations during sleep paralysis:

  • The intruder: sensed presence, fear, audio-visual hallucination; caused by hyper-vigilant state in the midbrain.

  • The incubus: physical sensations (chest being crushed, problems breathing, pain); caused by hyper polarisation of motor neurons (which maintains paralysis of muscles during REM sleep) on perceptions of respiration.

  • Unusual Bodily Experiences: sensations of the body flying, floating, rotating etc; caused by conflicts of internal and external activation related to body position, orientation and movement.

Psychologist J Allan Cheyne of the University of Waterloo explains this hallucination phenomenon as a two-system process. The inner-brain structures (the amygdale and related limbic structures) that make up the first system constantly monitor the surroundings for subtle cues to threats and respond accordingly to them; however, when activated by the REM state in the absence of real danger, and coupled with personal and cultural knowledge, this system conjures the uneasy feeling that an evil presence is close by. On the other hand, the second system, comprising the sensory and motor sectors of the brain, differentiates the individual from other creatures, and when stimulated will create hallucinations of a somatosensory and dissociative nature.

The Psychological and Physical Factor

There seems to be a psychological link between anxiety and hallucinations experienced during sleep paralysis. Anxiety is a multi-system response to a perceived threat or danger, the extreme onset of which will cause the release of a barrage of stress hormones such as epinephrine and hydrocortisone, which in turn trigger physical events related to the heart, lungs and nervous system – such as difficulty in breathing, increase of heartbeat rate and blood pressure, and conditions resembling a heart attack – basically messing up our body's regulation systems. This is because, unlike fear, whereby a person can get rid of stress hormones through fight-or-flight, anxiety represents situations in which the person can neither respond physically nor flee, thus causing their bodies to absorb all the biochemical changes of hyper-arousal. In this way, a person experiencing panic or anxiety during sleep paralysis is thus assaulted by internal audio-visual stimuli which produces hallucinations of danger and evil presences.

Other stress-related conditions such as post-traumatic stress disorder, fatigue, strenuous physical activity, radical changes in routine and jetlag may also bring about sleep paralysis by disrupting the sleep cycles and causing individuals to abruptly wake up from REM sleep in the middle of the night. Psychologists Richard J McNally and Susan A Clancy from Harvard University have also reported the link between childhood sexual abuse and sleep paralysis in adulthood.

Interestingly, the 14th-Century Swiss alchemist Paracelsus put forward his opinion that pregnant women were especially susceptible to sleep paralysis ('some people, especially women in child-bed, have been so oppressed in the night in their sleepe, that they have thought themselves to be as it were strangled, neither could they possibly cry out, or call any helpe, but in the morning have reported that they were ridden by a hag'), a hypothesis now supported by the recent findings by a Finnish medical study that reported the increase of such episodes in the second and third trimesters of pregnancy.

Sleep Paralysis and Narcolepsy

It has been speculated that sleep paralysis and narcolepsy may be linked in some way. Narcolepsy is another sleeping condition whereby the individual is prone to fall asleep unpredictably, at any time of day, and under any conditions (perhaps made most memorable in the movie Rat Race by Rowan Atkinson's character, who falls asleep at the most inopportune moments), and wakes up ten to 20 minutes later feeling refreshed. The sudden loss of muscle tone (known as cataplexy) when aroused or excited7 as well as the hallucinations experienced by individuals during a cataplectic episode (even as they remain conscious, although prolonged attacks may cause them to fall asleep) further suggest an association between these two conditions. However, it should be pointed out that these two conditions do not necessarily come hand-in-hand, as not all people with narcolepsy experience sleep paralysis and vice versa (the prevalence of sleep paralysis being 20 or 25 to 40 percent, and 0.03 to 0.16 percent for narcolepsy; cases of sleep paralysis associated with narcolepsy range from 40 to 60 percent).

Genetic Predisposition

The medical community remains divided on this issue, with some scientists believing there is a genetic link for sleep paralysis, and others attributing it to psychology and environment. The evidence currently in favour of genetic predisposition is anecdotal, however, and scientists have yet to isolate a gene responsible for the condition.


It would seem that some researchers in the field of sleep paralysis also believe that geomagnetism has something to do with the condition. The Social Science Department of the Everett Community College in Washington has speculated that people living in geologically active areas of the Pacific Ocean (the so-called 'Ring of Fire') experienced a higher incidence of sleeping paralysis, based on a study of SP frequency and its correlation with geomagnetic activity k-index values, along with research into folklore references to these experiences. This issue is currently open to debate.

Who Gets Sleep Paralysis?

Sleep paralysis is reported to have an adolescent onset (especially given that teenagers are among the most sleep-deprived people), with a starting age of 16 or 17, although psychologist Al Cheyne cites several large samples that have yielded consistent means of 17 years of age, with a sharp increase after ten and a sharper decline from 17 to the mid-20s. The incidence of sleep paralysis is low after the age of 30, although individuals in their seventh decade have reported experiencing this condition. In a survey carried out on a population consisting of individuals between the age of 20 and 40 who have experienced sleep paralysis, about two-thirds had experienced the hallucinations associated with this condition, the most common of which was the 'evil presence'; it was, however, not determined if the remaining third had experienced similar hallucinations, but had not reported them for psychological reasons, or had not given the experience much thought. Other studies reveal that between 25 and 40 percent of the world population8 have experienced sleep paralysis at least once, but that the distribution is uneven among different races9, although this may have more to do with psychosocial stress conditions than ethnic groups per se. As mentioned earlier, people who are predisposed to panic and anxiety attacks are also more prone to sleep paralysis.

It would also seem that sleeping on the back in the supine position predisposes a person to sleep paralysis – with an incidence of 60 percent of sleep paralysis reported to occur in this position.

Is Sleep Paralysis Harmful?

Imagine this - you wake up in the middle of the night and find yourself inexplicably unable to move. You don't know if, in your sleep, you may have somehow severely damaged your nervous system, or if something's just gone horribly wrong with your body; in fact, you don't know if you're ever going to be able to move again. And what's worse, there seems to be Something in the room with you, and it's hell-bent on committing horrible acts upon your paralysed body – and you can't do squat about it. Even when the paralysis breaks, you'll probably be wondering for long afterwards if you're still right in the head.

The greatest 'harm', so to speak, of experiencing sleep paralysis is psychological; for those who have never experienced it before, or have no prior knowledge of the condition, their first time may be terrifying. Indeed there are people who, before they had heard of this condition, believed themselves to be mentally ill – one young woman in particular kept on turning down marriage proposals from her boyfriend because she thought that her experiences implied that she was mentally unstable. Once knowledge is gained about this condition, however, people generally become more reassured and prepared when the next episode comes – if it ever does.

Unfortunately, a sizeable portion of the general population remains ignorant of sleep paralysis, thanks to its infrequent, transient nature and its relative harmlessness. Even more daunting is the fact that there is a tendency for psychiatrists to misdiagnose this condition as a mental health problem of sorts, which results in mistreatment with drugs that were never needed in the first place and possible dire consequences upon the individual's self-perception, not to mention the perception of those around him.

There may be a real – if low-risk – threat, however. Some scientists are now hypothesising that a very rare fatal condition known as Sudden Unexplained Nocturnal Death Syndrome (SUNDS) may be associated with sleep paralysis. SUNDS, which is genetically and functionally identical to the Brugada Syndrome, is characterised by abnormal cardiogram and death by ventricular fibrillation10; it has been proposed that death is caused by extreme muscle atonia during sleep paralysis, which causes even cardiac muscles and the diaphragm to paralyse.

Coping with Sleep Paralysis

Because sleep paralysis, though sometimes terrifying, is seldom harmful, most treatment methods and advice are usually designed towards simply helping people cope with an episode, and taking preventive measures to minimise incidence. The individual is generally advised to practice good sleep behaviour: namely getting enough sleep, reducing stress, maintaining a regular exercise schedule as well as a consistent sleep schedule, not engaging in activities likely to cause sleep disturbance (such as eating large amounts close to bedtime) and not sleeping in the supine (face-up) position11, which seems to contribute to the condition. In the event of an onset, the individual is also instructed to remain calm and relaxed as the condition will wear off within minutes, to attempt to make small movements (to break the paralysis), or at least mental ones (which is likely to result in sensations of astral projection and out-of-body experiences). If an individual remains apprehensive about this, he or she may also arrange for the sleeping partner to help by arousing the sleeper from the paralytic stage. Some literature even advises enjoying the sensation as, if the individual can maintain control of his or her anxiety, there is the likelihood that the sleeper will slip into lucid dream.

In extreme cases, where episodes persist for weeks to months, it may become necessary to treat the condition with medication. Treatment with Prozac-type anti-depressants to inhibit REM sleep has reportedly reduced the incidence of sleep paralysis in some cases – although it would also seem that these episodes tend to increase once the patient is taken off medication or given different drugs.

Sleep Paralysis, Superstitions and Folklore

Sleep paralysis embodies a universal, biologically-based explanation for pervasive beliefs in spirits and supernatural beings... The experience thrusts mentally healthy people into a bizarre, alternative world that they frequently find difficult to chalk up to a temporary brain glitch.
- David J Hufford, Director of the Doctors Kienle Centre for Humanistic Medicine.

It is a trend in societies that, when confronted with events that defy everyday logic, people turn to anthropomorphisation in an attempt to explain these bizarre occurrences. Natural disasters were interpreted as the wrath of deities, sudden bursts of light were visiting angels, and sunrises were attributed to the daily battle between Horus and Seth. When an obscure neurological condition such as sleep paralysis – and one that inspires such terror – occurs to people not equipped with the scientific understanding to comprehend it, it is understandable that they turn to their cultural roots and superstitions about malevolent entities... or may this have been how some myths were invented?

Many cultures, among which sleep paralysis seems to be common enough to warrant attention, have documented the occurrences of sleep paralysis. Terminology was developed independently by different cultures to describe similar phenomena. In the East there is the Indonesian 'tindihan' (to be weighted down), which is attributed to numerous causes from spirits to underwater reservoirs running beneath the sleeper's bed, and the Japanese analogue, 'kanashibari' (to tie with an iron rope). A study carried upon 100 Cambodian refugees in 2003 revealed that almost half reported experiencing at least one sleep paralysis episode annually. Most of these people also believed they were attacked by demons who were once people who had suffered unjust deaths, and had come to bring bad luck upon the living. In St Lucia in the West Indies, the entity 'kokma' is a frightening ghast of a dead baby12 who haunts and throttles people in their beds. The Thai and Koreans have names for these experiences as well: 'Phi um' (ghost-covered)/'phi kau' (ghost-possessed), and 'ka wi nulita' (scissors pressed). But perhaps the most accurate (if uninformed) description of sleep paralysis comes from the people of Laos:

You want to listen, you can't hear; you want to speak, you are dumb; you want to call out, you cannot; you feel you are dying, dying; you want to run away. You piss with fear in your sleep.

Ancient Western literature also seems to be littered with mythology-enshrouded examples of the hallucinations associated with sleep paralysis, all centred upon a named shape-shifting being of some sort that attacks in the night. One such creature is the Incubus (Latin), described by Kiessling as a half-man half-beast entity which attacked in the night, and whose name gave rise to the word night 'mare'. Other equivalents for this oppressive chest-crushing creature include 'mar/mare', (German), 'maire' (Old English), 'mara' (Old Norse), 'ephialtes' (Greek), 'muera' (Czech), 'cauchmar' (French), 'pesadilla' (Spanish), 'zmora' (Polish), and 'mar/mor' (Old Irish). Apparently the Europeans had more than one breed of these creatures: in Germany there were also the witch pressers ('hexendrücken') and elves ('alpdruck'); the Greeks called theirs 'pnigalion' (the choker) and 'barychnas' (the heavy breather).

Other cultures identify this evil entity as female. There are references in several different cultures to 'The Old Hag', who is responsible for compressing the chests of people who sleep on their backs, sometimes biting or choking sleepers, and who gained considerable renown in Shakespeare's Romeo and Juliet. In the East the demon is an evil female spirit called Ardat lili or Lilitu, who flies at night and attacks men in their sleep. The personification of the Hebrew succubus Lilith, whom apocryphal stories name as Adam's first wife13, and who was said to be the mother of these demons, was probably based on this Lilitu entity, as was the Roman Lamia.

Other than the fact that these beings were said to have half-human shapes, there is also the tendency to associate such supernatural creatures with maligned ghosts and gods. One early account of ephialtes came from the Greek historian Herodotus, who wrote of the spirit of Astrobacus, a deceased hero, who appeared to the wife of King Ariston of Sparta in her husband's borrowed form. Grecian and Roman ephialtes and incubi were also equated with forest and woodland deities such as Pan and Diana, and even Satyrs, Sirens and Silvani. Less common were these hallucinatory conditions attributed to supernatural animals such as the 'tomlui' (a big bird with many wings and talons) in Ireland, the 'tchutch-muton' (a fairy in the guise of a black sheep) in Neuchatel, the 'liderc' (a supernatural chicken) in Hungary, and even cats in various cultures. Angels, both good and fallen (including the Devil himself!), and watchers are not left out either in the school of incubus, and a large proportion of them were believed to be guardian spirits of humans whose unfortunate amorous adventures with human women spawned demons who further assaulted helpless sleepers at night. Cain was speculated to be one such progeny; interestingly the famous Anglo-Saxon poem Beowulf named the monster Grendel14 a descendent of this first murderer. Perhaps Cain couldn’t help being who he was, after all.

There was a sexual element in many of these nightmarish experiences as well. Many of these testimonies seem to concerned the paralysed sleeper being forced into sexual relations with the attacking demons – as a dissertation written at the University of Turingen in 1666 will attest – and the unpleasantness of these sexual alliances are concordant with reports of recent sleep paralysis studies. Then again, sceptics point out that such reports of sexual assaults may conveniently cover up evidence of self-gratification or illicit affairs, especially among people of the cloth for whom such practices were forbidden, or may simply have been erotic dreams.

Unfortunately, as time passed, people in Europe became increasingly obsessed with the witchcraft phenomenon, which they blamed for everything from the weather to medical conditions. The archaic figure of 'mara' gradually came to be associated with living persons15, and the blaming of nightmares upon witchcraft16 culminated in the horrific persecution and fiery deaths of innocents whom society maligned as witches.

Aliens or Paralysis?

It's surprising more of the neighbours haven't noticed.
- Carl Sagan, in response to the 1992 62-page Roper survey claiming that some 4 million Americans are victims of alien abduction.

A survey known as the Roper Poll was carried out between the months of July and September 1991 to study the incidence of alien abductions. The survey consisted of eleven questions regarding experiences of different events, of which five were indicator experiences17 for alien abduction. Published in 1992, the report was mailed to about a hundred thousand psychiatrists, psychologists and other health care professionals, urging them to be open-minded to the possibility that things are happening to people that, by traditional Western framework, cannot or should not be. If the results of this poll are to be believed, then a grand total of 4 million Americans and 100 million Earthlings have been abducted by aliens. If you work out the math, that comes up to about 1.55% of the world population – which means that every neighbourhood in the city would have at least one person who's an abductee!

Aside from the baffling question of why beings from a much more highly-developed civilisation would be interested to invest so much time and resources on repetitive experiments involving millions of subjects (not to mention why all these descriptions of aliens and alien encounters sound so oddly... human), the characteristics of many of these abductions sound strangely familiar. Many of these testimonies report flashing lights, buzzing sounds, tingling sensations, and a sense of panic brought on by the realisation that one's body is completely immobilised except for the eyes. And of course the presence of strange non-human figures, and a certain sensation of being packed off onto a spaceship.

False Recall?

Richard McNally, who has studied so-called alien abductees for the past decade, is convinced that these people were actually victims of sleep-paralysis hallucinations. Although his studies of ten people who had reportedly experienced alien abductions revealed that they reacted as strongly as those who have been deeply traumatised by events such as combat and sexual assault when presented with reminders of their experience, he also discovered that alien abductees were not only more prone to exhibit 'false recall and recognition' but also scored higher than other individuals on scales designed to detect fantasy proneness and the tendency to believe in unconventional phenomena. Other researchers in the field have also discovered that the likelihood of people reporting experiences of alien abduction increased with exposure to books and movies promoting the idea. Furthermore, as many as 60 percent of these alien abduction cases are linked to sleep, and the reported experiences involving sounds and smells, sensations of paralysis and levitation, and terror in the presence of alien figures closely resemble the hallucinations associated with sleep paralysis – especially since traumatic HHEs are as vivid as everyday experiences. Last of all, an experiment carried out by Susan Blackmore from the Department of Psychology of the University of the West of England upon young children and university undergraduates revealed that knowledge of the appearance and behaviour of abducting aliens seems to depend more on a person's exposure to pertinent media than on how many 'indicator experiences' the person has had.

McNally argues that for an alien abduction claim to be brought forth, five requirements must be met:

  1. A belief about supernatural phenomena such as astral projection and crystals.

  2. A rich fantasy life, claims to possessing certain psychic and healing powers, susceptibility to phenomena such as hypnotism, out-of-body experiences, and visions.

  3. Exposure to the 'alien culture' (ie. Movies and stories about alien abductions and sightings).

  4. Experiencing an onset of sleep paralysis and its accompanying hallucinations.

  5. Consultations or conversations with therapists (or, as Susan Blackmore suggests, support groups or hypnosis – a method not only unreliable for getting information, but also with the tendency to implant false ones) who ask inadvertently leading questions that causes distorted memories of trauma to surface.

However, researchers on the other side of the debate are not so easily convinced. Defenders of the abduction theory, such as John E Mack of the Harvard University Medical School, maintain that a sizeable portion of these abduction cases do not fit the sleeping paralysis bill, citing reports of abductions in remote areas where the populace are not exposed to UFO culture and involving people who are not asleep but wide awake and alert. Others suggest that the aliens may be clever enough to render their victims immobile before kidnapping them. It is equally unlikely that McNally’s findings will dislodge abductees from their firm conviction that they have experienced alien encounters. And perhaps they have good reason to. In spite of being traumatised by their experiences, most of these abductees nevertheless feel privileged to come into contact with beings from another world (not to mention many of them have gained considerable attention – and sometimes money – from making public testimonies of their abduction). Most of them, says McNally, 'ultimately interpret their experience as spiritually transforming.'

Whether or not all of these abductees have actually experienced sleep paralysis, it has been demonstrated that under certain conditions, such as extreme sleep deprivation, people are prone to dream or hallucinate with their eyes wide open, even when they lose little or no freedom of movement. As researcher Michael Persinger has demonstrated, it is possible, by electrically stimulating specific parts of the brain, to duplicate feelings of sensed presence and other sensations associated with out-of-body and near-death experiences, and the alien abduction phenomenon. It may be that this explanation for the abduction phenomenon may also apply to reports of spectral apparitions18.


Perhaps it would be befitting this article to end with an anecdote. In August 1983 the famous American sceptic Michael Shermer was a participant in the insane 3,100-mile non-stop transcontinental Race Across America. Having pedalled for a solid 83 hours (and 1,259 miles), he was exhausted and sleepy when his support crew pulled up so that he could take a sleep break. Unfortunately, the flashing of their headlights caused Shermer to enter a hallucinatory state, in which he believed his crew had turned into aliens from the 1960s TV series The Invaders (whose identity give-away was a stiff little finger) – and, in what was probably the biggest display of human pluck in an encounter with an alien, Shermer viciously interrogated the 'aliens' on both technical and personal matters, all the while staring at their fingers. He then entered the motor home, slept for a good 90 minutes and, upon waking, remembered nothing of his hour-and-a-half abduction.


Blackmore, S. 1998. Abduction by aliens or sleep paralysis? Skeptical Inquirer Vol 22(3).

Bower, B. 2005. Night of the Crusher. The waking nightmare of sleep paralysis propels people into a spirit world. Science News Online Vol 168(2).

Cheyne, JA. 2001. The ominous numinous: Sensed presence and 'other' hallucinations. Journal of Consciousness Studies Vol 8(5-7):133-150.

Conesa, J. 1995. Relationship between isolated sleep paralysis and geomagnetic influences: a case study. Perceptual and Motor Skills Vol 80(3 Pt 2):1263-73.

Cromie, WJ. 2003. Alien abduction claims examined: Signs of trauma found. Harvard Gazette, 20 February.

Davies, O. 2003. The nightmare experience, sleep paralysis, and witchcraft accusations - Focus on 'the Nightmare'. Folklore Vol 114(2):181-203.

Hinton, DE. 2005. The ghost pushes you down: Sleep paralysis-type panic attacks in a Khmer refugee population. Transcultural Psychiatry Vol 42(1): 46-77.

Hishikawa, Y and T Shimizu. 1995. Physiology of REM sleep, cataplexy, and sleep paralysis. Advances in Neurology Vol 67:245-271.

Kristof, ND. 1999. Sleep disorder may explain alien abduction stories: Brain-body 'disconnect' can cause terror. New York Times, Friday, July 9.

McNally, RJ and SA Clancy. 2005. Sleep paralysis, sexual abuse and space alien abduction. Transcultural Psychiatry vol 42(1):113-122.

Paradis, CM and S Friedman. 2005. Sleep paralysis in African Americans with panic disorder. Transcultural Psychiatry vol 42(1): 123-134.

Rowlands, B. 2001. In the dead of the night. The Observer, Sunday, November 18.

Shermer, M. 1998. Why people believe weird things. Pseudoscience, superstition and other confusions of our time. WH Freeman & Company.

1Definition of hallucination by Slade & Bentall: an experience of perception in the absence of an appropriate stimulus, but which has the impact of a conventional perception and is not under the control of the experiment. 2To be more accurate, the non-REM sleep consists of four stages, each lasting between five and 15 minutes.3Individuals who suffer from a rare syndrome called REM Sleep Behaviour Disorder do not experience paralysis during REM sleep, and are therefore potentially dangerous, depending on the nature of their dreams.4To be exact, the monoaminergic system and the REM-on system it regulates, the cholinergic system.5A hormone and neurotransmitter that constricts blood vessels and contracts smooth muscle tissue. 6Releasing epinephrine or a similar substance. Epinephrine is a hormone that stimulates the heart and increases blood sugar, muscular strength and endurance.7If there is a complete loss of tone, the individual may simply collapse.8The 1990 International Classification of Sleep Disorders reports 40-60 percent. 9One study reported the incidence of sleeping paralysis among volunteers with panic disorder as 59 percent for African Americans, and seven percent for white people; among community volunteers the percentages were 23 percent for African-Americans and six percent for white people.10Ventricular fibrillation is caused by a malfunction of the electrical activity in the main pumping chambers of the heart, which results in the heart muscles beating in an uncoordinated fashion. This prevents the normal flow of blood to the rest of the body, and if the situation is not quickly corrected by delivering electrical shocks to the victim's heart, the victim may suffer brain damage or die.11One investigator recommended sewing an obtrusive object, say a tennis ball, onto the back of one's night clothing to avoid rolling into the supine position during sleep – a method sometimes recommended for those with obstructive sleep apnoea. Then again, some people will sleep through anything.12Similarly, it was also a common belief in Ireland that dead, unbaptised babies were to blame for such nocturnal attacks.13Now popularised in the Vertigo comic series Lucifer as a fiercely independent woman who left because she refused to bow down to The First Man.14Not all literature enthusiasts agree on this matter. Peter Dickinson, author of The Flight of the Dragons, argues that it is clear from Grendel's description in the poem that it is a dragon.15It was said that ordinary females could become 'mara' by one of many ways. A Dalmatian girl born in a red caul would become a witch when she married; and Norwegian women who were born one of seven daughters, or of women who relieved labour pains by supernatural means, or who were wearing wolfskin girdles were candidates for 'mara'-hood as well.16Ironically, this fear of witchcraft would have very likely caused an onslaught of 'nightmares' to descend upon the populace. This is what's called a vicious cycle.17The five indicator experiences are: (1) waking up paralyzed with a sense of a strange person or presence or something else in the room (18 percent); (2) feeling that you were actually flying through the air although you didn't know why or how (10 percent); (3) experiencing a period of time of an hour or more, in which you were apparently lost, but you could not remember why, or where you had been (13 percent); (4) seeing unusual lights or balls of light in a room without knowing what was causing them, or where they came from (8 percent); and (5) finding puzzling scars on your body and neither you nor anyone else remembering how you received them or where you got them.18Interestingly, there is a recent newspaper report of how electromagnetism and the rise of electromagnetic devices are contributing to the decline of ghost sightings all over the world.

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Infinite Improbability Drive

Infinite Improbability Drive

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