Rose, N.J., Blackmore,S. and French, C.C.
Paper presented at the Parapsychological Association Annual Convention
Paris, August 2002
Sleep paralysis (SP) is a benign sleep disorder which involves the frightening experience of being unable to move at sleep onset or upon awakening, often accompanied by hypnagogic or hypnopompic hallucinations. While sleep paralysis is one of the symptoms of narcolepsy it also occurs in normal individuals (incidence estimates vary between 5% and 58%). A total of 196 cases of SP were collected and coded into a database of features associated with the experience. From the categories developed for the case collections, items for a questionnaire were created. This questionnaire was given to a mixed sample of 379 respondents. Along with the incidence for a number of experiential features, a principal components analysis was carried out to identify types of SP within the sample. Four components are identified and interpretive labels are suggested for each. The four were: ‘Visionary’ Experience, involving lots of ostensible ESP-type perceptions coupled with some kind of ‘revelation’ (either finding a solution to a problem or receiving guidance), seeing a tunnel of light was also associated with this component as were unexpected sexual feelings; Levitation Dream, which appears to be a false awakening involving the sensation that you are floating accompanied by buzzing noises in the head, bodily shaking, pain and migraine-like symptoms and seeing strange lights; Spiritual Assault (Old Hag) involved the presence of a hostile entity (commonly attributed to being a ghost or spirit), pressure on the chest, intense fear and tactile hallucinations all over the body; the final component has been labelled Panic Attack as the combination of the feeling you might be about to die, accompanied by the feeling that you cannot breathe, appears similar to the symptoms of a panic attack. Believers in the paranormal who had experienced SP reported more ostensibly paranormal features (and more features overall) during the episode than non-believers. Believers in the paranormal who had not personally experienced SP were more likely to interpret a description of the experience as reflecting a paranormal event and less likely to accept sceptical interpretations.
In the International Classification of Sleep Disorders (ICSD) sleep paralysis is defined as “a period of inability to perform voluntary movements either at sleep onset (hypnagogic or predormital form) or upon awakening either during the night or in the morning (hypnopompic or postdormital form)” (Thorpy, 1990). Sleep paralysis is often accompanied by dreamlike mentation and hypnagogic imagery, which is often frightening or threatening.
Hufford (1982) examined a widespread form of sleep paralysis called the ‘Old Hag’, which refers both to the terrifying experience and to the entity which allegedly attacks the victim. ‘Hag-riding’ and ‘hagging’ were the names commonly used to describe nocturnal assault by a witch in West Country England up until the early twentieth century (Davies, 1997). Settlers probably brought the name ‘hag-riding’ to Newfoundland. Hufford suggested that the experience of ‘Old Hag’ can be best understood as sleep paralysis with hypnagogic hallucinations.
Other names for the experience include; “Kanashibari” in Japan (Fukuda, Miyasita, Inugami & Ishihara, 1987), “The witch riding you” in the USA, “Kokma” attacks by the spirits of dead unbaptised babies in St Lucia, “Phi um” the feeling of being enveloped by a ghost in Thailand, “Hexendruchem” or passing witches in Germany, “Ha-wi-nulita” being squeezed by scissors in Korea, “Pesadilla” a nightmare in Mexico, and “Stand-stills” in the UK (Dahlitz & Parkes, 1993).
Quite recently sleep paralysis has been linked with the experience of ‘alien abduction’ French, 2001; Holden & French, in press). Hopkins, Jacobs and Westrum (1992) carried out a large survey through the Roper Organisation. They found that 18% of the Americans sampled reported the experience of sleep paralysis along with a feeling of presence. They controversially suggested that this experience was one of five key symptoms which indicated abduction by extraterrestrials. Spanos, Cross, Dickson, and DuBreuil (1993) studied Canadians who reported close contact with UFOs, and divided the experiences into intense and non-intense. The intense experiences were more often sleep-related, more often unpleasant, and a quarter described symptoms that could be interpreted as sleep paralysis. Blackmore (1998) suggests that the best explanation for many abduction experiences is that they are elaborations of the experience of sleep paralysis.
Sleep paralysis is commonly thought of as a symptom of narcolepsy. Hishikawa (1976) found that 57% of narcoleptic patients had suffered an episode. What has often been overlooked by medical practitioners is that isolated sleep paralysis also occurs in non-narcoleptics and often features in experiences which the victim reports as a supernatural attack. It is not entirely clear how common isolated sleep paralysis may be. One of the earliest surveys by Goode (1962) discovered an incidence of sleep paralysis of 4.7%. Hufford (1982) carried out a survey of Newfoundlanders which discovered a 15% incidence of ‘Old Hag’. Later studies found around 40% in Japan (Fukuda, Miyasita, Inugami & Ishihara, 1987), 58% among Chinese students (McClenon, 1988), 44% of nursing students in Nigeria (Ohaeri, Adelekan, Odejide & Ikuesan, 1992), 37% of undergraduate students in Hong Kong (Wing, Lee & Chen, 1994) and 21% in a sample of 1798 Canadian students (Spanos, McNulty, DuBreuil, Pires & Burgess, 1995). In a recent study in the UK, Blackmore (1998) found that 46% of a sample of 224 undergraduates, and 34% in a sample of 126 school children (aged 8 – 13) reported having had sleep paralysis.
In the sixties it was suggested that sleep paralysis was a dysfunction of the reticular activating system (e.g. Goode, 1962; Liddon, 1967). But later research has linked sleep paralysis with sleep onset REM periods (SOREMP) in narcoleptics (Hishikawa, 1976). Hishikawa, Koida, Yoshino, Wakamatsu, Sugita, Iijima, and Nan’no (1978) found that sleep paralysis and hallucinations occurred exclusively during SOREMP, with latency less than 2 minutes from the sleep-onset. Dahlitz and Parkes (1993) suggest that all types of sleep paralysis are due to inappropriate timing of REM sleep atonia, particularly when REM activity occurs at sleep onset.
The personalities of sleep paralysis sufferers were examined by Spanos et al. (1995). They found that a composite index of imaginativeness predicted occurrence and frequency of sleep paralysis, and the intensity of symptoms. There was no correlation with sexual or physical abuse, however physical abuse correlated with the intensity of the sleep paralysis. They did find correlations with vivid imagery (e.g. nightmare/terrors), imaginativeness, out of body experiences (OBEs), and hypnotizability. These findings led them to suggest that imaginative people tend to notice the paralysis more and that the true incidence of sleep paralysis may be higher, but ignored by many in the population. It has been shown (e.g. Allen & Nutt, 1993; Bell, Dixie-Bell & Thompson, 1986; Bell, Hildreth, Jenkins & Carter, 1988; Paradis, Friedman, & Hatch, 1997) that sleep paralysis and panic disorder are associated, although the nature of the relationship between the two remains unclear.
Although the incidence of SP and characteristics of people who experience it have been studied, there is comparatively little research on what the experience is actually like. Jones (1951) lists three cardinal features which distinguish the ‘nightmare’ (which through its original meaning of ‘night incubus’ refers to sleep paralysis) from other kinds of dreams: a feeling of agonizing dread, a sense of weight on the chest which interferes with respiration, and a sense of helpless paralysis.
Other researchers have examined the ‘symptoms’ of sleep paralysis from survey data. Fukuda, Inamatsu, Kuroiwa and Miyasita (1987) carried out a study of the Kanashibari phenomenon using a survey of 635 college students in Japan, 43% (273) of whom reported having had at least one episode of Kanashibari. They found that around 60% of participants felt anxiety or terror, 40% felt pressure on their chest, 30% felt someone was present, 30% had auditory hallucinations, 15% reported visual hallucinations and a similar proportion reported tactile hallucinations.
Wing et al. (1994) carried out a survey of 603 students in Hong Kong. 37% (223) reported at least one attack of ghost oppression. Of these 59% felt terror and 31% anxiety, 50% felt weight on their chest, 11% sensed someone was present, 23% had auditory events and a similar proportion reported visual hallucinations. 8% of respondents reported tactile hallucinations.
In a Canadian study of 1798 students, Spanos et al. (1995) found that 21% (382) of respondents reported at least one episode of sleep paralysis. Sleep paralysis attacks were examined for many of the same features that the Japanese and Hong Kong studies had found. They found that 66% of the sample were afraid, 35% felt pressure upon their chest (of which 6% of people saw someone pushing on their chest), 63% reported a presence (33% saw a person or being), 30% heard unusual noises (25% heard footsteps, and 18% heard their name), 23% saw unusual sights and 56% had unusual body sensations (32% reported being touched, and 27% felt floating sensations).
The underlying similarity of sleep paralysis reports from widely different cultural backgrounds suggest that there is a core of invariant features to this phenomenon (c.f. Spanos, et al. 1995). However, there is also some significant variation in terms of incidence of sleep paralysis and the features associated with it. There was no standardised method of data collection in these studies and differences may be due to item construction which may have caused response biases, so comparisons must be interpreted cautiously. However, these three studies found large differences in phenomenology, for instance ‘presences’ are reported at 11%, 30%, and 63%, ‘weight on the chest’ varies from around a third to a half of respondents, and ‘unusual bodily sensations’ (56%) rated much higher than tactile hallucinations (15% and 8%).
One problem for determining incidence is that ‘sleep paralysis experiences’ may possibly involve a number of distinct experiences, possibly involving different neurological mechanisms. Cheyne, Rueffer and Newby-Clark (1999) developed a three-factor structural model of hypnagogic and hypnopompic experiences based on their relations to both cultural descriptions of such states and REM neurophysiology. The three factors were: Intruder, which involved feelings of a presence, fear, auditory and visual hallucinations; Incubus, which involved pressure on the chest, breathing difficulties and pain; and Unusual Bodily Experiences, such as flying/floating sensations, out-of-body experiences and feelings of bliss.
The aim of this study was to collect descriptions of SP so as to obtain a better understanding of the phenomenology of the experience and identify key experiential features from descriptions of the experiences themselves.
We carried out two case collections over a period of two years. For the first study we placed advertisements in a number of specialist magazines and newsletters to obtain reports of sleep paralysis. In the second study we received letters reporting unusual experiences originally sent to X Factor magazine (a magazine devoted to examining UFOs and paranormal phenomena). There was no standardisation of report collection.
The purpose of these case collections was to create a database that could be used to broadly identify key features which characterise the state of sleep paralysis. For the purpose of deciding whether sleep paralysis was present we used the definition of sleep paralysis from ICSD (Thorpy, 1990). Features of the experience were classified under descriptive headings so that states and experiences associated with sleep paralysis could be identified and their incidence within our participant group estimated.
The reports from both collections were entered into a descriptive database which coded them under one or more of 34 categories. For the first study two people coded half the reports onto the database (NR and Kerry Gray). A third person, Caitlyn McCall, coded all the reports onto the database for the second study. NR checked approximately 10% of the entries by the other two coders. Whilst the process of checking was informal, few discrepancies were found and all three coders found the categories easy to identify when they occurred. By sorting the sets of experience within the database, secondary features of sleep paralysis, such as OBEs, presences, and purported psychic events, could be counted. A complete list of the categories appears in Table 1.
Table 1: Categories used to code cases.
|Age of respondent||Dreams|
|Experience of past lives or viewing past||Extraterrestrials|
|False awakening||Feelings of being pulled or touched|
|Feelings of flying, floating or falling||Feelings of pain or pins and needles|
|Guidance within a dream||Vibrations or electric humming noises|
|Hearing voices or laughter||Hypnagogic/ hypnopompic hallucinations|
|Hypnosis and hypnotic regression||Lucid dreams or dream control|
|Meditative states||Migraine or temporal lobe symptoms|
|Near Death Experiences (NDEs)||Night shift work|
|Nightmares or night terrors||Out of Body Experiences (OBEs)|
|Precognition or clairvoyance||Problem solving within a dream|
|Seeing flashing or bright lights||Seeing tunnels|
|Sensing benign or neutral presences||Sensing malign presences|
|Sex of respondent||Sexual or erotic feelings|
|Shaking or fitting||Sleep paralysis|
|Spirits, ghosts or apparitions||Telepathy|
For the first study we received 201 letters describing a variety of experiences, many of which included episodes of sleep paralysis. The age range of respondents was 8 to 87 years (average 34.3 years). 119 of the respondents were male, 73 were female (data was not available for 9 participants).
For the second study we received 184 letters. The age range of respondents was 9 to 59 years (average 24 years). 106 of the respondents were male, 66 were female (data was not available for 12 participants).
In the first study 128 respondents reported SP of which 40% were women and 56% were men (4% did not specify a gender). The age range for sleep paralysis reports was 11 to 78 years (average 31 years). There were 73 non-SP cases.
Table 2 shows the most common experiential features associated with sleep paralysis; the figures for non-sleep paralysis are given for broad comparison. The two strongest experiential features were malign presences (45% of the SP cases) and vibrations / electric humming / noise (41%). While the majority of the explanations given by participants were sceptical (23%) some respondents claimed supernatural explanations (spirits and ghosts, 16%) and a few linked the experiences with extraterrestrial contact (5%). Some respondents singled out night-working as a predisposing factor (9%) A majority of the non-SP cases involved dreams including episodes of lucid dreaming or apparent dream control.
Table 2: Results of first study.
|Feature||% SP Cases||% Non-SP Cases|
|Vibrations / Humming||41||11|
|Pulling / Touching||20||11|
|Benign / Neutral Presences||17||14|
|Voices / Laughter||16||7|
|Bright / Flashing lights||16||14|
|Pain / Pins and Needles||11||3|
In the second study, 68 cases of sleep paralysis were identified of which 44% were from women and 54% from men (2% did not specify gender). The age range for sleep paralysis reports was 13 to 59 years (average 27 years). There were 116 non-SP cases.
Table 3 shows the most common features of sleep paralysis for the second study, again figures for non-sleep paralysis cases are included for broad comparison. The most common categories were the same as for study one; malign presences (59%) and vibrations / electric humming / noise (38%). Explanations for sleep paralysis experiences were more evenly distributed in this study with sceptical explanations (7%), spirits and ghosts (7%) and extraterrestrial contact (6%) all equally prominent. The majority of non-SP cases involved extraterrestrials and strange lights (including UFO sightings). This is not surprising, given the nature of the magazine that supplied the accounts.
Table 3: Results of second study.
|Feature||% SP Cases||% Non-SP Cases|
|Vibrations / Humming Noise||38||10|
|Hypnagogic / Hypnopompic Halluc.||24||9|
|Voices / Laughter||19||4|
|Pain/Pins and Needles||13||3|
From the reports we received, and the analysis carried out, we suggest that the following description is typical of SP reports:
“I went to bed at my normal time, though I was a little overtired. As I lay on my back in bed and began drifting off to sleep, I suddenly woke up, but was completely unable to move. I could hear or feel a strange buzzing or vibrating noise inside my head, and at the same time I felt a horrible presence in the room with me. My eyes were open and I could see my bedroom. I could see this dark shape, like a shadow, standing at the end of the bed. I tried to call out, but I felt like I couldn’t breathe, and I could only manage a strangled cry. It felt like I had a heavy weight pressing down on my chest. I could feel this dark shape getting closer to me and I was terrified. I heard or felt it say something to me, but I couldn’t make out the words. It felt like it started to pull me upwards off the bed by my legs. I struggled, desperate to move or cry out, but could not. In a final effort I concentrated on moving one finger, and with a struggle I managed to move it just a bit. Then suddenly it was over, I broke free of the paralysis and the presence disappeared.”
The respondents were entirely self-selected, and reports were not standardised in any way. Also the categories used were derived from reading the reports themselves. However, both studies produced very similar results with regard to the strongest experiential features of sleep paralysis. In line with survey findings (Fukuda et al., 1991; Wing et al., 1994; Spanos et al., 1995) we found that feelings of fear or terror, presences, and tactile or auditory hallucinations often accompany sleep paralysis.
Sleep paralysis victims often consider the presence they feel during the experience as malign, but not exclusively it seems. Some of our respondents reported presences which were either neutral or even benign. In addition to this we also discovered another feature which occurs within sleep paralysis, that of vibrating or electric humming noises.
The majority of people in our study offered no explanation for the experience, although some offered a rational or ‘sceptical’ explanation. A minority interpreted their experience as involving supernatural or extraterrestrial entities, and some believed that their experience was somehow brought on by supernatural attack or alien interference.
Based on the categories determined in the case collection a questionnaire was created so that the incidence of these experiential features could be better determined.
Table 4 lists the items included in the sleep paralysis experience inventory. The items were adapted from the categories developed for the case collection. Respondents were first asked the question, “Have you ever had the experience when going to sleep, or perhaps as you were waking up, of suddenly feeling paralysed; as if you could not move your arms or legs and could not speak or cry out?” Those who answered ‘yes’ to this item were asked to consider one instance of this experience and indicate (by simply ticking ‘yes’ or ‘no’ to each item) which of the 30 items in the inventory had been present during, just before or just after the feeling of paralysis.
Of course, not all respondents would have experienced sleep paralysis. Non-sleep paralysis respondents (those who answered ‘no’ to the question above) were asked to read the typical description of sleep paralysis (given above) and invited to rate their preference for a variety of explanations for such a experience. Table 5 lists the explanations given. Half of the items (10) were created as broadly paranormal explanations for the description (e.g. a psychic experience or attack by a ghost). The other half of the items were created as more sceptical explanations (e.g. a hallucination, or product of drink or drugs). These items were generated informally from the various explanations offered in the case reports.
Alongside this questionnaire, participants were also asked to complete the most widely used measure of paranormal belief; the Revised Paranormal Belief Scale (Tobacyk & Milford, 1983; Tobacyk, 1988). It consists of 25 items on seven dimensions, with a 5-point rating scale ranging from strongly disagree to strongly agree, and a ‘belief score’ is obtained by adding the ratings.
Table 4: Items in the Sleep Paralysis Experience inventory
|1. The feeling that a non-hostile or friendly presence was nearby, though no one was there.|
|2. The feeling that you could not breathe.|
|3. The sense that your whole body was shaking or vibrating.|
|4. Psychokinesis (e.g. moving or influencing an object with the mind alone).|
|5. The sense of a ghost or spirit in the room with you.|
|6. Unexpected sensations of pain.|
|7. The feeling or belief that you were dying or might be about to die.|
|8. The feeling that someone/thing was pulling or touching your chest or abdomen, though no one was there.|
|9. Contact with what you thought to be an extraterrestial entity.|
|10. Feeling you were awake, only to discover later that you were still dreaming at the time.|
|11. The sensation of flying.|
|12. The feeling that someone/thing was pulling or touching your arms or legs, though no one was there.|
|13. Perceiving information about a distant event which you could not have otherwise known.|
|14. Seeing a tunnel of light.|
|15. Unexpected sexual or erotic feelings.|
|16. Receiving some kind of guidance or advice.|
|17. Viewing events which had happened in the past but that you could not have otherwise known.|
|18. Finding the solution to a problem you had been thinking about all day|
|19. Suffering migraine-like symptoms.|
|20. The sensation that someone/thing was pressing down on your chest.|
|21. The feeling that a hostile or malign presence was nearby, though no one was there.|
|22. The sensation of intense ‘humming’ or ‘buzzing’ in your head.|
|23. Perceiving information about the future which you could not have otherwise known.|
|24. Hearing voices in the room, though no one was there.|
|25. Telepathy (i.e. mind to mind communication).|
|26. The sensation of floating.|
|27. The feeling of intense fear.|
|28. The feeling that someone/thing was pulling or touching your head, though no one was there.|
|29. Seeing strange lights in the room.|
|30. The feeling that you had left your body and could move around without it.|
Table 5: Explanations for a description of sleep paralysis
1 = Strongly Disagree 2 = Disagree 3 = Uncertain 4 = Agree 5 = Strongly Agree
|1. The person had a psychic experience|
|2. The person had an unusual dream|
|3. The person was having an out-of-body experience|
|4. It was caused by the effect of drugs or alcohol|
|5. The person was being assaulted by a supernatural being|
|6. It was a nightmare|
|7. The person was experiencing an alien abduction|
|8. It was some kind of sleep disorder|
|9. It was an attack by the devil|
|10. The person had a paranormal experience|
|11. It was the result of some physical illness|
|12. The person was being attacked by a spirit or ghost|
|13. The person was having a hallucination|
|14. It was the result of some mental illness|
|15. The person had a dream and thought they were awake|
|16. The person was having a near death experience|
|17. It was contact with an alien being|
|18. The person was possessed by a supernatural being|
|19. The person was imagining things|
|20. It was the result of a psychological problem|
There was a total of 379 participants (mostly students) in the questionnaire study of whom the vast majority (82%) were female (310 women compared to 69 men). There was a wide range in the age of participants (15 to 61) with the average age being 24 years.
In the questionnaire study 116 respondents reported having had sleep paralysis (44.1%). The most common features of sleep paralysis are the ones we might have expected to see; fear 67%, hostile presence 42%, pressure on chest 37%. Nearly half of SP sufferers (47%) indicated that they felt that they could not breathe. 64% indicated that the experience of sleep paralysis appeared to involve false awakening (i.e. a dream in which you thought your were awake, and only when you wake up do you realise you were dreaming). 39% of respondents indicated the presence of a ‘ghost’ during the experience. Table 6 shows the incidence of the various features accompanying the experience of paralysis.
Table 6: Features of sleep paralysis experiences
|Incidence||Feature of Experience|
|37%||Pressure on chest|
|36%||About to die|
|30%||Humming / buzzing in head|
|28%||Pull/touch arms or legs|
|8%||Tunnel of light|
Seven of the items on the questionnaire involved ostensibly paranormal events (items 4, 5, 9, 13, 17, 23, and 25) and a score was created from the responses to these items to reflect the general paranormal character (interpretation) of the sleep paralysis episode. Another score was generated simply from the sum of all experiential elements reported by a participant (i.e. if a participant reported 6 different features then they would have a score of 6). This total included the paranormal items. These scores were correlated (using Pearson’s correlation coefficients) against the belief score from the Revised Paranormal Belief Scale. There was a significant and positive correlation between the belief score and the number of paranormal features (r = 0.22, n = 115, p = 0.02, two-tailed) and the total number of experiential features reported (r = 0.20, n = 115, p = 0.03, two-tailed).
The other 263 respondents indicated that they had never had sleep paralysis. The most commonly preferred explanations were; ‘nightmare’, ‘unusual dream’, ‘false awakening’, ‘imagining things’, and ‘hallucinations’. After these the next most preferred was ’sleep disorder’. A list of the explanations respondents preferred for the example description of sleep paralysis is given in Table 7.
Table 7: Preferred explanations for an example of sleep paralysis.
The score is simply the sum of the Likert scores for that item across all respondents. It is given here merely to indicate how strong a preference respondents showed to each item. The lowest possible score is 263 (if everyone scored an item 1), and the highest is 1315 (if everyone scored an item 5).
The Likert scores were summed for the 10 items which were more paranormal and the 10 which were more sceptical, to form a ‘paranormal explanation score’ and a ‘sceptical explanation score’ for each participant. There was a significant and positive correlation (Pearson’s) between preference for a paranormal explanation and the participant’s score on the Revised Paranormal Belief Scale (rs = 0.63, n = 261, p < 0.001, two-tailed). There was also a significant and negative correlation between preference for a sceptical explanation and the participant’s belief score (rs = -0.20, n = 261, p = 0.001, two-tailed).
In order to examine variety of sleep paralysis experiences a principal components analysis with varimax rotation was carried out using SPSS on 30 items from the questionnaire for the sample of 116 sleep paralysis cases. Ten factors with eigenvalues above 1 were extracted, but examination of the scree plot indicated that after 4 factors changes in successive eigenvalues were small. A principal components extraction was then carried out for 4 components and varimax rotation applied. Table 8 lists the 4 components, and interpretive labels are suggested for each.
Extraction Method: Principal Component Analysis.
Rotation Method: Varimax with Kaiser Normalization.
Component 1: ‘Visionary’ Experience
|23.||Perceiving information about the future which you could not have otherwise known.||.778|
|13.||Perceiving information about a distant event which you could not have otherwise known.||.763|
|25.||Telepathy (i.e. mind to mind communication).||.635|
|18.||Finding the solution to a problem you had been thinking about all day||.599|
|17.||Viewing events which had happened in the past but that you could not have otherwise known.||.598|
|16.||Receiving some kind of guidance or advice.||.567|
|15.||Unexpected sexual or erotic feelings.||.516|
|14.||Seeing a tunnel of light.||.469|
Component 2: Levitation Dream
|22.||The sensation of intense ‘humming’ or ‘buzzing’ in your head.||.747|
|29.||Seeing strange lights in the room.||.696|
|11.||The sensation of flying.||.660|
|19.||Suffering migraine-like symptoms.||.603|
|26.||The sensation of floating.||.595|
|6.||Unexpected sensations of pain||.564|
|4.||Psychokinesis (e.g. moving or influencing an object with the mind alone).||.459|
|10.||Feeling you were awake, only to discover later that you were still dreaming at the time.||.427|
|3.||The sense that your whole body was shaking or vibrating.||.422|
Component 3: Spiritual Assault / Old Hag
|21.||The feeling that a hostile or malign presence was nearby, though no one was there.||.673|
|8.||The feeling that someone/thing was pulling or touching your chest or abdomen, though no one was there.||.643|
|20.||The sensation that someone/thing was pressing down on your chest.||.577|
|28.||The feeling that someone/thing was pulling or touching your head, though no one was there.||.571|
|5.||The sense of a ghost or spirit in the room with you.||.567|
|12.||The feeling that someone/thing was pulling or touching your arms or legs, though no one was there.||.516|
|27.||The feeling of intense fear.||.431|
Component 4: Panic Attack
|7.||The feeling or belief that you were dying or might be about to die.||.668|
|2.||The feeling that you could not breathe.||.588|
There are obvious issues with the sample, and this limits the ability to generalise from these results. The sample was heavily dominated by women over men, and whilst the majority were students the sample was not exclusively composed of students. However, despite this there are several similarities in the incidences of experiential features between the case studies and the questionnaire sample and this is encouraging. If features from such widely differing samples occur with similar incidence, then the features themselves may well occur with a fairly robust incidence across the population.
Firstly about 44% of the respondents indicated that they had at some time or another experienced an episode of paralysis at sleep onset or upon waking. This compares well with an earlier study carried out by Blackmore (1998) which found an incidence of 46% in a sample of undergraduates. However, given the wide variation in the incidence of sleep paralysis in the literature, it seems that a general figure of ‘somewhere between a third and a half’ of the population is a fair estimate of the incidence of SP.
The incidence of the two most common features which emerged from the case studies compares fairly well to the incidence from the questionnaire study. In the case studies malign presences were found in 45% and 59% of cases involving sleep paralysis. In the questionnaire study 42% of people reported a malign presence accompanying their experience of paralysis. Vibrations and humming or buzzing noises were found in 41% and 38% of the SP cases, this compares fairly well with 30% humming / buzzing in head for the questionnaire.
Other features reported in previous studies were also found in our study such as fear, tactile and auditory hallucinations. Two thirds of respondents to the questionnaire indicated that intense fear was a feature of the SP, which makes fear the single most common experiential feature of sleep paralysis experience. Tactile hallucinations were also very common; 37% reported the pressure on the chest so commonly associated with sleep paralysis. Other somatosensory hallucinations were also common such as pulling or touching the chest (31%), arms or legs (31%) and head (19%). There were also unusual bodily sensations such as the feeling of floating or flying (37% and 36% respectively). There was the auditory hallucination of hearing voices for a quarter of the participants, and also visual hallucinations for some with 22% seeing strange lights, and 8% seeing a tunnel of light (more usually associated with out-of-body or near-death experiences).
While the sample is small for a principal components analysis and any conclusions drawn must therefore be tentative, the components found form groups of experiences which were fairly easy to recognise and name. The four were: ‘Visionary’ Experience, involving lots of ostensible ESP-type perceptions coupled with some kind of ‘revelation’ (either finding a solution to a problem or receiving guidance), seeing a tunnel of light was also associated with this component as were unexpected sexual feelings; Levitation Dream, which appears to be a false awakening involving the sensation that you are floating accompanied by buzzing noises in the head, bodily shaking, pain and migraine-like symptoms and seeing strange lights; Spiritual Assault (Old Hag) involved the presence of a hostile entity (commonly attributed to being a ghost or spirit), pressure on the chest, intense fear and tactile hallucinations all over the body; the final component has been labelled Panic Attack as the combination of the feeling you might be about to die, accompanied by the feeling that you cannot breathe, appears similar to the symptoms of a panic attack.
There are number of possible interpretations of the relationship between sleep paralysis and panic attacks. The two conditions obviously overlap in terms of symptomatology (difficulty breathing, feeling that one is about to die) but they are not identical (for example, panic attacks typically do not involve inability to move). It is possible that episodes of sleep paralysis are enough to trigger panic attacks in those susceptible to the latter. There might, however, be a common neurophysiological basis to the disorders. Panic disorder is thought to be associated with abnormal regulation of the noradrenergic system (Charney & Heninger, 1986), which is also implicated in narcolepsy (Allen & Nutt, 1993). If this is the case then it might be seen as a positive finding, as therapeutic methods employed to assist people to recognise and avoid panic attacks might in some cases also be employed to help people cope with sleep paralysis episodes. Indeed, Paradis et al. (1997) report that of eleven participants suffering from both panic disorder and recurrent isolated sleep paralysis (ISP), five reported improvements with respect to the latter following cognitive-behavioural treatment directed only at the former. They speculate that “a decrease in panic symptoms leads to an improvement in quality of sleep, which in turn, may lead to a reduction in ISP episodes” (p. 74).
Two of the other postulated types of sleep paralysis, Spiritual Assault and Levitation Dream, have some overlap with the factors identified by Cheyne et al. (1999). Spiritual Assault appears to combine the principle elements from Cheyne’s Intruder and Incubus; presence, fear and pressure on the chest. Levitation Dream has the flying/floating sensations, labeled Unusual Bodily Experiences in the Cheyne et al study, but the Levitation Dream also includes pain, buzzing and shaking, and false awakening.
Finally we have the rather unusual ‘Visionary’ Experiences group of experiential features which appear to have no parallel with factors identified by the Cheyne et al study or examples from the literature reviewed in the introduction. However, states which invoke lucid dreams, hypnagogic imagery or waking imagery are often utilised by both the occult traditions and parapsychology to elicit ostensible magical or psychic effects, and so it should probably come as no surprise that we find ostensibly psychic experiences being reported during sleep paralysis. It appears that sufferers of SP not only report attacks by ghosts and witches but also apparent psychic experiences such as seeing the past, clairvoyance or precognition, or communication/telepathy.
For sufferers of sleep paralysis it appears that belief in the paranormal correlates with both more experiential features generally (perhaps believers pay more attention to, or have better recollection of the experience) and also (perhaps unsurprisingly) more experiential features which could be described as paranormal. This evidence alone cannot exclude the possibility that the phenomena themselves are real and through personal experience people come to believe. For example, Blackmore (1984) found personal experience of the paranormal to be the single most common reason for belief.
However, the results from the participants who did not have sleep paralysis offer an alternative explanation. It appears that believers in paranormal phenomena were likely not only to prefer paranormal explanations for a description of sleep paralysis, but also more likely to reject sceptical explanations. It is interesting to speculate how those believers might go on to interpret an episode of sleep paralysis if they ever suffered one in the future. It seems evident that believers would draw upon the interpretative framework of their paranormal beliefs to help explain and describe the unusual experience, given that they appear ready to do so even for a description of such an experience. This would suggest that sometimes ostensibly paranormal experiences are likely to be unusual experiences which are interpreted as paranormal (by virtue of previously held beliefs) rather than that beliefs arise directly from a genuinely paranormal experience.
On the other hand, even many of the secular or sceptical ‘folk’ explanations for sleep paralysis are no more comforting. Whilst the most commonly preferred explanations for the ‘typical’ description of sleep paralysis were that it was a nightmare, an unusual dream or a false awakening experience, there was also preference shown for explanations such as the involvement of drugs/alcohol, or the result of a psychological problem or even a sign of physical or mental illness.
Sleep paralysis is a benign sleep disorder, but because it is often terrifying and bizarre it is possible for sufferers to become overly concerned. All three authors have found, during the course of this research, that simply reassuring sufferers that this experience has a name and is not dangerous is usually enough to alleviate some of that concern. There is also the possibility that some manifestations of sleep paralysis may have sufficient similarity to panic attacks that therapeutic methods to help alleviate panic may also help people who suffer from sleep paralysis. It is hoped that this study will help promote further dissemination of knowledge about this common sleep phenomenon in order to alleviate the fears of sufferers and encourage proper understanding.
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