Sleep Paralysis Research Paper

Cult Med Psychiatry
DOI 10.1007/s11013-013-9327-x
ORIGINAL PAPER

Rates and Characteristics of Sleep Paralysis in the General Population of Denmark and Egypt
Baland Jalal • Devon E. Hinton

Ó Springer Science+Business Media New York 2013

Abstract In the current research we report data from two studies that examined rates and characteristics of sleep paralysis (SP) in the general population of Denmark and Egypt. In Study I, individuals from Denmark and Egypt did not differ in age whereas there were more males in the Egyptian sample (47 vs. 64 %); in Study
II, individuals from Denmark and Egypt were comparable in terms of age and gender distribution. In Study I we found that significantly fewer individuals had experienced SP in Denmark [25 %
(56/223)] than in Egypt [44 % (207/470)] p \ .001.
In Study II we found that individuals who had experienced at least one lifetime episode of SP from Denmark (n = 58) as compared to those from Egypt
(n = 143) reported significantly fewer SP episodes in a lifetime relative to SP experiencers from Egypt (M = 6.0 vs. M = 19.4, p \ .001). SP in the Egyptian sample was characterized by high rates of SP (as compared to in Denmark), frequent occurrences (three times that in the Denmark sample), prolonged immobility during
SP, and great fear of dying from the experience. In addition, in Egypt, believing SP to be precipitated by the supernatural was associated with fear of the experience and longer SP immobility. Findings are discussed in the context of cultural elaboration and salience theories of SP.
Keywords

Sleep paralysis Á Rates Á Culture Á Fear Á Anxiety Á Trauma

B. Jalal (&)
Center for Brain and Cognition, University of California at San Diego, 0109, Mandler
Hall,
9500 Gilman Drive, La Jolla, CA 92093-0109, USA e-mail: [e-mail]
D. E. Hinton
Harvard Medical School, Boston, MA, USA

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Introduction
Sleep paralysis (SP) is characterized by a state of involuntary immobility that occurs immediately prior to falling asleep or upon waking (Hobson 1995; Paradis et al.
2009). During SP the individual experiences an inhibition of voluntary muscles
(atonia); that is, the medulla and pons contain a system that actively suppresses skeletal muscle tone during REM through inhibition of spinal motor neurons, possibly by glycinergic inhibitory interneurons in the spinal cord (Kandel et al.
2000). However, in spite of the gross motor paralysis, the sensory system is clear and ocular and respiratory movements intact, which lead the individual to experience a transient period of bodily paralysis accompanied with semiconsciousness.
Moreover, the perceptual activity of dreaming, another feature of REM sleep, may also become activated during SP leading the person to experience auditory and visual hallucinations (Cheyne et al. 1999). These vivid sensory experiences, hypnogogic (upon falling asleep) or hypnopompic (upon awakening) hallucinations, include the subjective experience of sensing a terrifying presence, hearing footsteps, levitation, autoscopy, and seeing an amorphous ‘‘intimidating’’ figure approach the body (Hufford 1982). Even the imagining of sexual assault is not uncommon during
SP (Jalal et al. in press). Though certain aspects of the biologically driven phenomenology of SP have been found to be stable across cultures, in each culture these hallucinoid features will be interpreted in a number of culturally specific frameworks, with supernatural explanations ranging from ghost and demon attacks
(e.g., Hinton et al. 2005b; Wing et al. 1994; Ness 1978) to extra-terrestrial abduction
(e.g., McNally and Clancy 2005; for review see Hinton et al. 2005a).
The distressing nature of SP potentially may generate psychopathology by fear mechanisms and escalating cycles of arousal. For example, SP is associated with high levels of fear and distress and it is much more feared than ordinary dreaming: dreams are feared about 30 % of the time as found in a combined sample of college students and elderly individuals (Schredl and Doll 1998; Sharpless and Barber 2011) whereas one web-based study (Cheyne et al. 1999) found that as many as 90 % of a
German college student sample reported that their SP was associated with fear.
Similarly, Sharpless et al. (2010) found in a psychiatric sample that 69 % of research participants reported clinically significant levels of fear associated with their SP.
Research suggests that SP rates are higher in individuals with PTSD (Hinton et al. 2005a, b, c; Ohayon and Shapiro 2000; Yeung et al. 2005), panic disorder
(Bell et al. 1986, 1988; Friedman and Paradis 2002; Paradis and Friedman 2005;
Yeung et al. 2005), generalized anxiety disorder and social anxiety (Otto et al. 2006;
Simard and Nielsen 2005). Higher rates of elevated anxiety sensitivity have also been found in individuals with SP (Ramsawh et al. 2008). Aside from the link between SP and anxiety, SP has also found to be associated with depression and dissociative symptoms (McNally and Clancy 2005). Overall these findings indicate that stress, chronic fear, and anxiety may serve as predisposing factors increasing an individual’s odds of experiencing SP.

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Research does not provide a conclusive answer as to how SP rates differ in various populations which may be one reason that SP is often overlooked by
clinicians.
While some studies suggest that SP is a common phenomenon with between 18 and 40 % of the general population having experienced it at least once in a lifetime (Cheyne et al. 1999; Fukuda et al. 2000; Wing et al. 1999) other studies have found prevalence rates as low as 6 %. Moreover, research indicates that SP may be more common in certain populations and among certain ethnic and cultural groups. For instance, data indicate that college students and psychiatric patients in general have higher rates of SP ranging from 25 to 42 % reporting at least one lifetime episode (e.g., Awadalla et al. 2004; Sharpless and Barber 2011). Furthermore, research has found SP rates to be highest in individuals with African and
Asian descent (e.g., Paradis and Friedman 2005). Specifically among psychiatric patients, Cambodian refugees have the highest rates of SP (Hinton et al. 2005a, b, c); among college students Asians report higher rates of SP compared to other ethnic groups (Sharpless and Barber 2011).
It has been suggested that culture may influences rates of SP. For example,
the salience hypothesis posits that for certain groups SP may receive greater cultural elaboration (Spanos et al. 1995). As such when SP is interpreted through a specific cultural filter (e.g., as a supernatural experience) it may take on greater salience, in some cases leading to increased fear and potentially making it a traumatic event. As proposed by Hinton et al. (2005a, b, c) such fright associated with SP may lead the person to acquire a conditioned fear of the experience which through escalating cycles of arousal and activation of brain fear systems may result in more nighttime awakening and thus more SP (see too, Bell et al. 1988; Ohayon and Shapiro 2000;
Paradis et al. 1997). In this respect, high rates of SP have been found among
Cambodian refugees who have various cultural interpretations of the phenomenon including attributing the hallucinations to dangerous visitations by the ghosts of those who died horrible deaths during the Pol Pot genocide and/or attributing paralysis to a ‘‘weak heart’’ that may suddenly stop functioning (Hinton et al.
2005a, b, c).
Given the current state of the literature, it is important to compare rates of SP in groups with distinct ethnic backgrounds. Moreover, it is pivotal to understand how
SP rates vary in groups with different cultural interpretations and conceptualization of SP. Finally, while much research has examined once-in-lifetime occurrence of
SP, researchers often overlook mean lifetime frequency rates (i.e., average number of SP episodes in a lifetime), and features of SP such as duration, frequency of hallucinations, and level of fear associated with the experience; such features may in turn may provide important clues about the pervasiveness of SP in a given population as a potential medical condition.
In the current studies we explored rates and characteristics of SP in Denmark and
Egypt. The two countries in question are particularly suited for comparison given the distinct ethnic and cultural background of their respective populations. For instance, while Denmark is one of the most secular regions of the world, where people score the lowest on measures of religiosity (Zuckerman 2008), Egypt has a majority Arab population many of whom adopt the Islamic faith and culture as the cornerstone of their identity (Abdo 2000). Moreover, recent research has found that

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SP experiencers in the general population of these two countries interpret SP in very different lights. While the vast majority of SP experiencers in Denmark (95 %) interpret their SP as a non-supernatural event precipitated by physiological factors
(e.g., ‘‘brain malfunctioning’’ and ‘‘reduced blood flow in the brain’’ etc.), many SP experiencers in Egypt (71 %) interpret SP as a supernatural experience, with many
(48 %) specifically believing that SP is caused by malevolent Jinn attacking them; according to traditional Islamic belief the Jinn are spirit-like creatures that may possess, terrorize, and even kill their victims. Moreover, the malevolent Jinn are traditionally thought to constitute a source of madness, witchcraft, and satanicinspired nightmares (Jalal et al. in press) (for more details on Jinn assaults see Jalal et al. in press; Amer and Jalal 2012).

Study Aims
Below we describe two studies that compare the rate and phenomenology of SP in
Denmark and Egypt. In Study I we compared lifetime occurrence of SP among individuals from the general population of Denmark and Egypt. We hypothesized that lifetime occurrence of SP would be lower among individuals from Denmark compared to individuals from Egypt. In Study II, the aim was to compare the average number of SP episodes in a lifetime among individuals from Denmark and
Egypt who reported experiencing at least one episode of SP. In Study II we hypothesized that lifetime frequency rates of SP would be lower among individuals from Denmark compared to individuals from Egypt. Finally, we examined characteristics and beliefs associated with SP in Denmark and Egypt.

Study I
Method
Participants
The participants included a sample comprised of individuals from Copenhagen,
Denmark (n = 223), and a sample from Cairo, Egypt (n = 470) (see Table 1).

Table 1 Participants’ demographic characteristics for Study I
Sample type

N

% Male

Age

Education

M (SD)

RNG

M (SD)

RNG

Denmark

223

47.1

30.5 (11.5)

18–70

19.7** (6.5)

4–46

Egypt

470

64.3**

31.7 (13.4)

18–78

12.2 (5.3)

0–27

* P \ .05, ** P \ .01

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Measures
Assessment of SP All participants were screened for once-in-a-lifetime occurrence of SP using the first item on the SP Questionnaire designed by second author Devon
E. Hinton. The SP Questionnaire has previously been utilized in studies in the US where it was administered orally to research participants in its full form (e.g., Yeung et al. 2005; for details on this instrument see method section of Study II).
The first item on the SP Questionnaire is formulated, ‘‘Upon going to sleep or awakening, have you ever had the experience of wishing to move or speak but being unable to do so?’’ To avoid false positives, and consistent with the methodology of
Hinton et al. (2005a, b, c), if participants answered affirmatively to this question they were asked to describe their episode to ensure that the participant had experienced a genuine SP episode.
Prior to data collection all items on the SP Questionnaire were carefully examined. For instance, the first author (who is fluent in English, Danish, and
Arabic) consulted native speakers in all three languages. These native speakers assisted in assessing whether the items could be translated from English to both
Arabic and Danish without modification. Furthermore, studies using the questionnaire were conducted at both sites. In light of these attempts to assess the utility of the item, and in line with Jalal et al. (in press), it was decided that the questionnaire was rendered in such simple English language that it could easily be administered in both Arabic (Egyptian dialect) and Danish without modification.
Procedures
Participants provided informed consent and basic demographic information. This study was approved by the Institutional Review Board for dealing with human subjects at the University of Copenhagen and the American University in Cairo. A variety of means were used to recruit opportunity samples at the research sites.
Participants from both Denmark and Egypt were approached in different locations and community settings, including work places (municipality and other governmental settings, shops, and private businesses), shopping malls, university campuses and other educational institutions, and health care settings. Participants were informed about the nature of the study and then asked to participate. Upon consenting, participants were screened by trained research assistants (all native speakers in the population in which they were collecting data). The first item of the
SP Questionnaire (e.g., Yeung et al. 2005) was orally administered to participants.
Participants recruited in Cairo, Egypt, were screened in Arabic (Egyptian dialect), all individuals from Copenhagen, Denmark, in Danish.
Data Analyses
The demographic characteristics of participants, including age, gender, and education level were compared using an Independent Samples t test, and the v2 test. The v2 test was further used to compare lifetime occurrence of SP.

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Results
Comparison of Lifetime Occurrence of SP in Demark and Egypt
Fewer individuals from Denmark (n = 56/223) reported having experienced SP compared to individuals from Egypt (n = 207/470), namely, 25 versus 44 %, v2
(1) = 22.5, p \ .001 (see Fig. 1).
Study II
Method
Participants
The participants included a sample of individuals from Copenhagen, Denmark
(n = 58), and a sample from Cairo, Egypt (n = 143) (see Table 2).
Measures
Religiosity Religiosity was measured as: ‘‘How important is religion to you?’’
Response categories were on a seven-point Likert scale (1 = not important at all and 7 = very important).
Assessment of SP The SP Questionnaire designed by second author Devon E.
Hinton has previously been utilized in studies in the US where it was administered
Fig. 1 Percentage of Danish
(n = 223) and Egyptian
(n = 470) individuals having experienced sleep paralysis at least once in a lifetime

Table 2 Participants’ demographic characteristics for Study II
Sample type

Denmark
Egypt

N

Age

Education

M (SD)

RNG

M (SD)

RNG
11–44

58

57

25.1 (9.0)

18–55

16.6** (4.9)

143

57

26.0 (8.1)

18–67

13.5 (4.2)

* P \ .05, ** P \ .01

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orally to research participants (e.g., Yeung et al. 2005). The questionnaire is comprised of 13 open- and closed-ended items and is rendered in simple English. The questionnaire includes questions on the frequency of SP (e.g., lifetime, past year and past month), usual duration of SP, and emotional reactions to the experience (including fear of the experience). The questionnaire also include items on the nature of the hallucinatory experiences during SP, causal explanations of SP, and measures taken to prevent further SP episodes. Moreover, consistent with the methodology undertaken by Hinton et al. (2005a, b, c), if participants answered affirmatively to the first item of the SP Questionnaire, which aims to establish whether the participant has undergone
SP, they were asked to elaborate on their experience.
Procedures
Participants provided informed consent and basic demographic information. This study, similar to Study I, was approved by the Institutional Review Board for dealing with human subjects at the University of Copenhagen and the American
University in Cairo. The participants from the participants from Denmark and Egypt were recruited through referrals by colleagues and acquaintances as well as announcements in community settings. For all samples, a non-random convenient sampling technique known as ‘‘snowballing’’ or chain referral was utilized to increase sample sizes; this was done by asking participants to refer other individuals to our study (e.g., family, friends, and student colleagues etc.), who they believed may have experienced SP at least once in a lifetime.
Participants were informed about the nature of the study and then asked to participate. In order to meet eligibility to participate in the study individuals must have had experienced at least one SP episode in their lifetime. The SP Questionnaire was orally administered to participants. Participants from Cairo, Egypt, were interviewed in
Arabic (Egyptian dialect); individuals from Copenhagen, Denmark, in Danish.
Data Analyses
The demographic characteristics of participants, including age, gender, and education level were compared for all samples using an Independent Samples t test and the v2 test. The t test and v2 test were also used to compare lifetime frequency rates of SP and to examine characteristics of SP. Finally, a biserial correlation and phi correlation test was used to explore correlates of supernatural causal explanations of SP.
Results
Comparison of Lifetime Frequency Rates of SP in Demark and Egypt
As hypothesized individuals from Denmark had significantly lower lifetime frequency rates of SP compared to individuals from Egypt (M = 6.0, SD = 8.6 vs. M = 19.4, SD = 39.9), t(152) = -3.6, p \ .001 (see Fig. 2).

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Fig. 2 Lifetime frequency rates of sleep paralysis of Danish
(n = 58) and Egyptian
(n = 143) individuals

Characteristics of SP in Denmark and Egypt
Immobility During SP Individuals from Denmark reported that they were usually unable to move during SP for less time compared to individuals from Egypt
(M = 4.2 min, SD = 3.3 min, vs. M = 5.2 min, SD = 7.0 min), t(191) = 1.90, p \ .05.
Fear of Dying from SP Significantly less individuals from Denmark feared dying from SP compared to individuals from Egypt (17.2 vs. 54.1 %), v2 (1) = 22.5, p \ .001.
Hallucinations During SP Among Danish individuals 31 % (18 out of 58) experienced hallucinations during SP, whereas 34 % (49 out of 143) of Egyptian individuals experienced hallucinations during SP, v2 (1) = .4, ns.
Correlates of Supernatural Causal Explanations of SP Among Danish individuals, ascribing supernatural causes to SP (e.g., ghosts or spirits) was associated with higher levels of religiosity (rb = .37 p \ .01) and older age (rb = .43, p \ .01).
Moreover, in the Danish sample believing SP to be precipitated by the supernatural was associated with experiencing hallucinations during SP (ru = .32, p \ .05). On the other hand, in the Danish sample believing SP to be precipitated by supernatural entities was not associated with fear of the experience (ru = .11, ns) or longer duration of immobility (rb = .24, ns).
Among Egyptians endorsing supernatural causal explanations of SP was associated with higher levels of religiosity (rb = .21, p \ .05) and older age
(rb = .37, p \ .001). Similarly, among Egyptians endorsing supernatural causes to
SP was associated with experiencing hallucinations during SP (ru = .27, p \ .01).
Finally, among Egyptians believing SP to be precipitated by supernatural entities was significantly associated with fear of the experience (ru = .20, p \ .05) and longer duration of immobility during SP (rb = .24, p \ .01).

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Case examples of SP
Case 1 Kasper (names in this section are pseudonyms) is a 22 year college student from Copenhagen, Denmark. He does not view himself as religious. He has experienced SP five times in his life. His SP usually occur when he is exhausted or when sleeping during the daytime. He believes that his SP is precipitated by brain mechanisms. Although he feels uncomfortable during SP, he does not characterize his SP as particularly frightening. Kasper’s SP last a couple of minutes on average and are accompanied by sensations of a presence and heavy constrain on his chest.
Case 2 Jibaly is a 27-year-old businessman from Cairo, Egypt. He describes himself as a fervent believer in the Islamic faith, and adheres to the five daily prayers. Jibaly has experienced SP about 50 times in his life. During SP, he sees an evil looking Jinn hovering over him (resembling an ‘‘ugly’’ old man), whispering his name, choking him, pressing down on his chest, and even violating him sexually to the point of ejaculation. The experience is a long-fought-struggle for Jibaly lasting on average between 5 and 10 min, often culminating with the Jinn entering into his body. Jibaly believes that the Jinn is not able to kill him because of his religious commitment and chanting of Qur’anic verses during the attacks. Jibaly has several friends who have similar SP experiences; in the past they have advised each other on rituals they can perform to keep the Jinn at bay.
Discussion
As hypothesized Study I showed, consistent with previous research suggesting that
SP is the least common in Caucasian majority populations (Sharpless and Barber
2011), that a lower number of individuals from Denmark (a predominantly
Caucasian population) had experienced SP compared to individuals from Egypt.
Although the vast majority of SP prevalence studies have been conducted using college student samples, high lifetime rates of SP have been found in other nonCaucasian ethnic groups and general populations with no psychiatric symptoms, including among African Americans (39 %) (Bell et al. 1984), and the general populations of Japan (34 %) and Nigeria (38.2 %) (Arikawa et al. 1999; Ohaeri et al. 2004).
Moreover as anticipated, SP experiencers from Denmark had on average less SP episodes in a lifetime compared to SP experiencers from Egypt. The current results add to the body of literature suggesting that recurrent episodes of SP are less common among majority Caucasian populations compared to other ethnic groups. For example,
Bell et al. (1984) found higher incidents of recurrent isolated sleep paralysis (RISP) among African Americans (47 %) compared to Caucasian participants (10 %). Bell et al. (1984) were the first to develop diagnostic criteria for ‘‘recurrent ISP’’ which include experiencing SP at least four times per year.
Put together the current studies suggest that not only do more Egyptians experience SP compared to individuals from Denmark (44 vs. 25 %), but also those who undergo SP among Egyptians experience it about three times more often

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(M = 19.4 vs. M = 6.0). The finding that many Egyptian SP experiencers report a high numbers of SP episodes in a lifetime suggests that recurrent SP or RISP thought to be rare (e.g., McCarty and Chesson 2009) may be more common among certain ethnic and cultural groups. In brief, these results indicate that examining once-in-a-lifetimes rates of SP alone may not provide adequate information when it comes to understanding the pervasiveness of SP; in order to gain a more comprehensive understanding of SP in a given population research needs to pay more attention to lifetime frequency rates.
In the Study II, the number of individuals who reported hallucinations during SP did not differ in Denmark and Egypt (31 vs. 34 %). The percentage of SP sufferers who experience hallucinations during SP has found to vary in the literature. For example, while 44.5 % of Nigerians from the general population report hallucinations during SP (Ohaeri et al. 2004), up to 75 % of Canadian college students report
SP with hallucinations. In the later study, around 5 % of Canadian students had full range of hallucinations including visual and auditory hallucinations (Cheyne et al.
1999).
On the other hand, we did find that Egyptians had longer SP episodes (i.e., longer immobility) compared to Danish individuals (5.2 vs. 4.2 min). Long duration of SP
(5.3 min) has similarly been found among Cambodian refugees (Hinton et al. 2005a, b, c). As mentioned, according to the salience hypothesis for certain groups SP may receive greater cultural elaboration, such that the experience and associated symptoms (e.g., immobility) take on greater salience (Hinton et al. 2005a, b, c;
Spanos et al. 1995). In this respect, recent research (Jalal et al. in press) has found that many Egyptians interpret their SP as assaults by malevolent spiritual beings known as the Jinn in Islamic culture. Similarly, Hinton et al. (2005a, b, c) found long durations of SP among Cambodian refugees (1975–1979) whose cultural understanding of SP includes visitations from deceased relatives who died during the Pol Pot period. Thus both among Egyptians and Cambodian refugees, such terrorized immobility may serve as a trauma cue leading to conditioned fear and consequently the activation of fear centers in the brain (e.g., certain limbic structures including the amygdala) (Bell et al. 1988; Ohayon and Shapiro 2000;
Paradis et al. 1997). These arousal mechanisms may in turn lead to increased nighttime awakenings particularly during REM sleep and in effect more SP (Hinton et al. 2005a, b, c). Thus prolonged immobility may provide one explanation for the high rates of SP in the Egyptian sample.
Moreover, the salience hypothesis posits that in groups where individuals share information about the phenomenon of SP (e.g., its cause and remedies) usually report higher rates. This argument is based on the idea that the availability of cognitive categories influences the recognition and the level of attention paid to subtle and ambiguous events (Neisser 1976). Thus, individuals in such cultures have been ‘‘culturally primed’’ to recognize subtle and sometimes ambiguous symptoms as cues of paralysis and then seek out to confirm these by attempting movement
(Spanos et al. 1995).
Such expectancy-induced sensitivity to the recognition of SP may further explain the high rates of SP reported in Egypt where SP is often understood and discussed in the context of Jinn attacks and where people frequently seek out Islamic healing

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remedies to get rid of SP (Jalal et al. in press). That is, these individuals may be hyperalert to SP symptomatology and thus attempt movement to confirm their suspicion of a Jinn attack. By contrast, in a place like Denmark SP is regarded as an idiosyncratic event where members of the cultural group rarely discuss and often are unfamiliar with SP. For this reason in such cultures the paralysis is likely to go unnoticed. Moreover, it is given that the higher the intensity of the symptomatology
(e.g., the longer duration of immobility) the more the experiencer is likely to notice their paralysis (Spanos et al. 1995). While over 50 % of Egyptians in the current study reported that they feared dying from their experience, only 17 % of individuals from Denmark expressed such fear of SP. These findings dovetail with previous research suggesting that SP experiencers in Denmark unlike Egypt give less cultural significance to the experience, the majority of whom interpret their SP as a physiological precipitated event (95 %) (Jalal et al. in press). If we contrast such interpretation of SP with the common Egyptian conceptualization of the phenomenon as a Jinn attack such exaggerated fear in the latter case seems in its place. That is, the Jinn in Islamic culture has a long and elaborate tradition, regarded traditionally as a major cause of madness; for instance, the etymology of the word
‘‘mad’’ or ‘‘insane’’ in Arabic majnoon is derived from the word Jinn, literally meaning one who is possessed by a Jinn. Moreover, Iblis the Quranic equivalent of the Devil in Biblical tradition is regarded as a malevolent Jinn whose aim is to antagonize human beings. In this regard, it is also not surprising that in Egypt believing SP to be precipitated by the supernatural was found to be significantly associated with fear of the experience.1 This finding is in contrast to the Danish sample where we did not find such an association.
Moreover, the fear of death associated with SP among Egyptians may be related to the occurrence of Sudden Unexpected Nocturnal Death Syndrome (SUNDS). For example, a link has been suggested between the traditional narrative of SP as a nocturnal pressing spirit attack and SUNDS-related events as narrated in folk tradition, including the victim appearing aware, paralysis of the body, lying in a supine position, a crushing sensation on the chest, and intense fear and terror (Adler
2011). Thus it is possible that in some extreme cases the cultural impact on SP and its interpretation may lead to nocebo-caused death; this would be a powerful example of mind–body interaction possibly showing the socio-cultural and psychological influence on physiological states, in this case resulting in a psychogenetic death. The presence of such a culture-specific syndrome in Egypt would be consistent with the Islamic belief that the Jinn may cause death, and help explain why many SP sufferers in Egypt as opposed to Denmark believe SP to be fatal. (This can of course not be directly concluded from the present data, but remains an open question that should be explored in future research studies.)
Higher levels of religiosity and older age were associated with endorsing supernatural causal beliefs of the experience in both Denmark and Egypt.
Religiosity may be associated with supernatural explanations of SP in that individuals who are religiously inclined might, irrespective of cultural context, more
1

The suggestion that religion may be a source of distress as opposed to comfort only has been made by
Guthrie (1993).

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readily resort to religious or spiritual explanations when encountering a phenomenon as potentially uncanny as SP. Similarly, individuals who are older in age may generally be more ensconced in a traditional world view relative to younger individuals, and thus more likely to favor a supernatural interpretation of SP.
Experiencing hallucinations during SP was correlated with endorsing supernatural causal beliefs of SP in both Denmark and Egypt. This finding is again not surprising as individuals who experience SP accompanied with hallucinations (e.g.,
‘‘sensing a terrifying presence’’ or seeing an amorphous ‘‘intimidating’’ figure etc.) may come to interpret these as supernatural in origin. Thus for some SP experiencers such hallucinations might serve as a validation of the existence of the supernatural. For instance, it is worth mentioning that research (Hufford 2005;
Jalal et al. in press) has found that experiencing SP may lead individuals to become more religious. One such example is Jalal et al. (in press) who found that many SP experiencers in Egypt due to the uncanny nature of their SP episode grow stronger in their Islamic faith. Similarly, Hufford (2005) found in a North American context that SP experiencers become stronger in their Christian faith as a consequence of undergoing SP. Overall these findings suggest that not only might faith and religious beliefs shape supernatural interpretations of SP, but also the peculiarity of SP itself may likewise propel the formation of such supernatural explanations.
Moreover, the notion that SP may corroborate the belief in the supernatural is analogous to research findings that in some cultures dreaming about encounters with supernatural beings, serves as experiential evidence and verification of their existence and power (e.g., among the Asabano tribe of Papa New Guinea; see
Lohmann 2000). Such a corroborating link between dream states (e.g., ordinary dreaming and SP) and the supernatural may especially be the case in cultures where dreaming are perceived as ‘‘real’’ experiences of the soul, as is the case in both
Islamic Egypt and Papa New Guinea (Jalal et al. in press; Lohmann 2000).
Certain limitations of the present studies need to be mentioned. First of all, we did not assess sleep disorders, so it is possible that some participants had SP due to narcolepsy.2 Furthermore, in Study I there were a higher percentage of males in the
Egyptian sample compared to the Danish sample. While female participants in the general population of Egypt for socio-cultural reasons are less accessible than males, future research should aim at a more even gender distribution. Finally, the non-random sampling methods utilized in both studies, including the ‘‘snowballing’’ method used in Study II, are likely to yield a homogenous sample, and thus potentially biased data.
Also given the positive association between anxiety and SP, it is important to keep in mind the current social unrest in Egypt; that is, such a political climate may contribute to elevated fear and anxiety among Egyptians and thus potentially higher
SP rates. Likewise, lower standards of living in general (as found in Egypt as
2

While we are not able to rule out that SP occurred as a symptom of narcolepsy given that this sleep disorder is very uncommon, the vast majority of SP cases reported in this study are bound to represent isolated sleep paralysis (ISP). For example, Ohayon et al. (2002) found in a large study of 18,980 randomly selected participants representative of the general population of five European countries (UK,
Germany, Italy, Portugal and Spain) that .047% met a diagnosis of narcolepsy according to the
International Classification of Sleep Disorders (ICSD).

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opposed to Denmark) are typically associated with chronic stress, anxiety, and disruptive sleep patterns which may predispose to having SP. Thus it should be emphasized that variables—other than culture shaped beliefs about the experience—could also partly explain the high rates of SP among Egyptians relative to
Danish participants.
High rates of SP, prolonged immobility during SP, and fear of dying from the experience were preeminent characteristics of the Egyptian sample. Similarly, unlike Denmark in Egypt, believing SP to be precipitated by the supernatural was associated with fear of the experience and longer SP immobility. It may be that the kind of cultural elaboration given to SP in Egypt makes the experience and associated symptoms more salient, directly influencing rates of SP and the degree of fear associated with experience in Egypt. In this respect, future research needs to specifically address how SP is associated with psychopathology, particularly anxiety, and PTSD in this region of the world.
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