Cult Med Psychiatry
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.
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
D. E. Hinton
Harvard Medical School, Boston, MA, USA
Cult Med Psychiatry
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...
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