Risk factors for isolated sleep paralysis in an African American sample: a preliminary study

Associations between sleep variables and ostensibly paranormal experiences and paranormal beliefs: A scoping review

Night-time is a period of great significance for many people who report paranormal experiences. However, there is limited understanding of the associations between sleep variables and seemingly paranormal experiences and/or beliefs. The aim of this review is to improve our understanding of these associations while unifying a currently fragmented literature-base into a structured, practical review. In this pre-registered scoping review, we searched for relevant studies in MEDLINE (PubMed), PsycINFO (EBSCO), Web of Science and EMBASE using terms related to sleep and ostensibly paranormal experiences and beliefs. Forty-four studies met all inclusion criteria. All were cross-sectional and most investigated sleep paralysis and/or lucid dreaming in relation to ostensibly paranormal experiences and paranormal beliefs. Overall, there were positive associations between many sleep variables (including sleep paralysis, lucid dreams, nightmares, and hypnagogic hallucinations) and ostensibly paranormal experiences and paranormal beliefs (including those of ghosts, spirits, and near-death experiences). The findings of this review have potential clinical implications such as reducing misdiagnosis and treatment development and provide foundations for further research. Our findings also highlight the importance of understanding why so many people report 'things that go bump in the night'.

The associations between paranormal beliefs and sleep variables

Previous studies have found significant associations between paranormal beliefs and sleep variables. However, these have been conducted on a small scale and are limited in the number of sleep variables investigated. This study aims to fill a gap in the literature by investigating paranormal beliefs in relation to a wide range of sleep variables in a large sample. Participants (N = 8853) completed a survey initiated by the BBC Focus Magazine. They reported on their demographics, sleep disturbances and paranormal beliefs. Poorer subjective sleep quality (lower sleep efficiency, longer sleep latency, shorter sleep duration and increased insomnia symptoms) was associated with greater endorsement of belief in: (1) the soul living on after death; (2) the existence of ghosts; (3) demons; (4) an ability for some people to communicate with the dead; (5) near-death experiences are evidence for life after death; and (6) aliens have visited earth. In addition, episodes of exploding head syndrome and isolated sleep paralysis were associated with the belief that aliens have visited earth. Isolated sleep paralysis was also associated with the belief that near-death experiences are evidence for life after death. Findings obtained here indicate that there are associations between beliefs in the paranormal and various sleep variables. This information could potentially better equip us to support sleep via psychoeducation. Mechanisms underlying these associations are likely complex, and need to be further explored to fully understand why people sometimes report "things that go bump in the night".

Risk factors of sleep paralysis in a population of Polish students

BACKGROUND

Sleep paralysis (SP) is a transitional dissociative state associated with the REM sleep phase that affects approximately 28.3% of the student population during their lifetime. The reasons for the high prevalence of SP in the student population are not entirely clear. Research indicates possible influencing factors such as the intensification of anxiety symptoms, a tendency to worry, the presence of PTSD symptoms, and behavioral factors such as the consumption of psychoactive substances (caffeine, alcohol, nicotine), sleep deprivations and poor sleep hygiene. The study aimed to assess the prevalence of SP and determine the risk factors for the occurrence of SP in the population of Polish students.

METHODS

The study used a battery online consisting of a set of questionnaires 1) a personal questionnaire, 2) the SP-EPQ, 3) the PCL -5, 4) the STAI-T, 5) the PSWQ. The questionnaire was sent via Facebook to 4500 randomly selected students from different universities in Poland. The questionnaire was completed by 2598 students. To unify the participant sample, people over 35 were excluded from the study (45 students). Ultimately, data from 2553 students were analyzed.

RESULTS

A total of 33.14% of individuals experienced at least one episode of SP in their lives. The highest odds ratio for SP was associated with: the presence of three or more health problems (OR: 2.3; p = 0.002), the presence of any mental disorder (OR: 1.77; p = 0.002), including mood disorders (OR: 2.07; p = 0.002), suffering from at least one somatic disease (OR: 1.34; p = 0.002), a high level of anxiety as a constant personality trait (OR: 1.20; p = 0.035) and smoking (OR: 1.48; p = 0.0002), alcohol consumption (OR: 1.52; p < 0.0001), physical activity (OR: 1.31; p = 0.001).

CONCLUSIONS

The results of our research indicate that a large proportion of students experienced isolated sleep paralysis. Mental and somatic health problems and lifestyle factors were found to predispose individuals to this disorder. Due to the numerous risk factors for SP, it is necessary to conduct additional research to confirm the impact of these factors and to investigate the mechanisms of their influence on SP.

"It Started After Trauma": The Effects of Traumatic Grief on Sleep Paralysis

Adverse life events are associated with the often-terrifying REM sleep parasomnia of sleep paralysis (SP), but the impact of bereavement on SP has not been specifically examined. This exploratory, mixed-methods study (N = 168) includes qualitative data from 55 participants who described factors they believed led to their SP. Of these, almost half with a traumatic loss listed death-related precipitants. In unadjusted (bivariate) negative binomial regression models, traumatic death, time since death, religiosity, and age estimated increased SP frequency in the prior month, prior year, or both. In multivariable models, traumatic death, time since death, and age estimated increased frequency in the prior month, prior year, or both. Unexpectedly, in all models, as compared to death ≥9 years earlier, prior month SP was greater with death 1-6 years earlier, but not <1 year earlier. Discussion includes the possible role of social constraints in traumatic grief trajectories and care provider recommendations.

Sleep Paralysis among Professional Firefighters and a Possible Association with PTSD-Online Survey-Based Study

The prevalence of sleep paralysis (SP) is estimated at approximately 7.6% of the world’s general population. One of the strongest factors in the onset of SP is PTSD, which is often found among professional firefighters. Our study aimed to assess in the professional firefighter population (n = 831) (1) the prevalence of SP, (2) the relationship between SP and PTSD and (3) the relationship between SP and other factors: the severity of the stress felt, individual tendency to feel anxious and worried and lifestyle variables. The incidence of SP in the study group was 8.7%. The high probability of PTSD was found in 15.04% of subjects and its presence was associated with 1.86 times the odds of developing SP [OR = 1.86 (95% CI: 1.04–3.33); p = 0.04]. Officers who experienced at least 1 SP during their lifetime had significantly higher results in the scales: PCL-5, STAI-T, PSWQ. The number of SP episodes was positively correlated with the severity of symptoms measured by the PCL-5, PSS-10, STAI and PSWQ questionnaires. Further research is needed to assess the importance of SP among the firefighter population in the context of mental and somatic health and to specify methods of preventing SP episodes.

Beliefs about sleep paralysis in Turkey: Karabasan attack

The present study examined explanations of sleep paralysis (SP) in Turkey. The participants were 59 college students recruited in İstanbul, Turkey, who had experienced SP at least once in their lifetime. Participants were administered the Sleep Paralysis Experiences and Phenomenology Questionnaire (SP-EPQ) in an interview. When asked whether they had heard of a name for SP, the vast majority (88%) mentioned the "Karabasan"-a spirit-like creature rooted in Turkish folk tradition. Seventeen percent of the participants believed that their SP might have been caused by this supernatural creature. Thirty-seven percent of participants applied various supernatural and religious methods to prevent future SP attacks such as dua (supplicating to God), reciting the Quran, and wearing a musqa (a type of talisman inscribed with Quranic verses). Case studies are presented to illustrate these findings. The Karabasan constitutes a culturally specific, supernatural interpretation of the phenomenology of SP in Turkey.

Sleep paralysis in Italy: Frequency, hallucinatory experiences, and other features

Previous research has found supernatural beliefs about sleep paralysis (SP) to be very prevalent in Italy, with over one third of SP sufferers believing that their SP might have been caused by a supernatural creature known locally as the Pandafeche. The current study further examined features of SP in Italy. All participants had experienced SP at least once in their lifetime. Participants were recruited from the general population (N =  67) in the region of Abruzzo. The Sleep Paralysis Experiences and Phenomenology Questionnaire (SP-EPQ) was orally administered to participants. As hypothesized, we found that Italians from the general population reported high lifetime rates of SP, prolonged duration of immobility during the event, and great fear of the experience (with as many as 42% of SP sufferers fearing that they could die from the experience), all of which were particularly elevated as compared to cultures where there are no such elaborate traditions of SP (e.g., Denmark). In addition, 78% of participants experienced some type of hallucination during their SP. The results we present here suggest that cultural beliefs about SP in Italy (e.g., as being caused by the Pandafeche, as reported elsewhere) potentially can profoundly shape certain aspects of the experience - a type of mind-body interaction.

Prevalence and Clinical Picture of Sleep Paralysis in a Polish Student Sample

Sleep paralysis (SP) is a psychobiological phenomenon caused by temporary desynchrony in the architecture of rapid eye movement (REM) sleep. It affects approximately 7.6% of the general population during their lifetime. The aim of this study was to assess (1) the prevalence of SP among Polish students in Lublin (n = 439) using self-reported online surveys, (2) the frequency of SP-related somatic and psychopathologic symptoms, and (3) the factors potentially affecting the occurrence of symptoms among people experiencing SP. We found that the incidence of SP in the Polish student population was slightly higher (32%) than the average prevalence found in other student populations (28.3%). The SP clinical picture was dominated by somatic symptomatology: 94% of respondents reported somatic symptoms (most commonly tachycardia, 76%), 93% reported fear (most commonly fear of death, 46%), and 66% reported hallucinations (most commonly visual hallucinations, 37%). The number of SP episodes was related to sleep duration and supine position during sleep. The severity of somatic symptoms correlated with lifestyle variables and anxiety symptomatology. Our study shows that a significant proportion of students experience recurrent SP and that this phenomenon is associated with fear and physical discomfort. The scale of the phenomenon requires a deeper analysis.

Sleep Paralysis, a Medical Condition with a Diverse Cultural Interpretation

Sleep paralysis (SP) is a state associated with the inability to move that occurs when an individual is about sleeping or just waking. It could occur in healthy individuals as isolated SP. It has also been linked with other underlying psychiatry, familial, and sleep disorders. Statistics show that 8% of the general population suffers from SP. Although this value has been described inaccurately, there is no standard definition or etiology to diagnose SP. There are several speculations describing SP in the current literature. These descriptions can be viewed as either cultural-based or medical-based. The disparity among cultural or ethnic groups and medical professionals in identifying SP has led to the various approaches to managing the condition. This review aims to medically describe SP and how it is interpreted and managed among various cultural groups.

Relationships between sleep paralysis and sleep quality: current insights

Sleep paralysis is the unusual experience of waking up in the night without the ability to move. Currently little is known about the experience, despite the fact that the vast majority of episodes are associated with extreme fear and in a minority of cases can lead to clinically significant levels of distress. The aim of this work was to review the existing literature pertaining to the relationship sleep paralysis has to sleep more generally, measured both with subjective questionnaires and objective laboratory recordings. In terms of subjective sleep variables, worse sleep quality has been found in multiple studies to be associated with increased odds of sleep paralysis occurrence. In addition, insomnia symptoms (but not a diagnosed insomnia disorder) have also been found to predict sleep paralysis. Associations between sleep paralysis and other unusual and/or threatening sleep experiences such as nightmares, exploding head syndrome, and lucid dreaming have been reported. In terms of objective measurements, the limited literature to date shows sleep paralysis to be a "mixed" state of consciousness, combining elements of rapid eye movement sleep with elements of wakefulness. Future research needs to focus on longitudinal designs to disentangle the direction of effects and more typically employ a broader assessment of sleep paralysis that better captures associated features such as hallucinations, fear, and distress.

Prevalence Rates of the Incubus Phenomenon: A Systematic Review and Meta-Analysis

BACKGROUND

The incubus phenomenon is a paroxysmal sleep-related disorder characterized by compound hallucinations experienced during brief phases of (apparent) wakefulness. The condition has an almost stereotypical presentation, characterized by a hallucinated being that exerts pressure on the thorax, meanwhile carrying out aggressive and/or sexual acts. It tends to be accompanied by sleep paralysis, anxiety, vegetative symptoms, and feelings of suffocation. Its prevalence rate is unknown since, in prior analyses, cases of recurrent isolated sleep paralysis with/without an incubus phenomenon have been pooled together. This is unfortunate, since the incubus phenomenon has a much greater clinical relevance than isolated sleep paralysis.

METHODS

PubMed, Embase, and PsycINFO were searched for prevalence studies of the incubus phenomenon, and a meta-analysis was performed.

RESULTS

Of the 1,437 unique records, 13 met the inclusion criteria, reporting on 14 (k) independent prevalence estimates (total N = 6,079). The pooled lifetime prevalence rate of the incubus phenomenon was 0.19 [95% confidence interval (CI) = 0.14-0.25, k = 14, N = 6,079] with heterogeneous estimates over different samples. In selected samples (e.g., patients with a psychiatric disorder, refugees, and students), prevalence rates were nearly four times higher (0.41, 95% CI = 0.25-0.56, k = 4, n = 1,275) than in the random samples (0.11, 95% CI = 0.08-0.14, k = 10, n = 4,804). This difference was significant (P < 0.001).

CONCLUSION

This review and meta-analysis yielded a lifetime prevalence of the incubus phenomenon in the general population of 0.11 and, in selected samples, of 0.41. This is slightly higher than the prevalence rates in previous analyses that included cases of recurrent isolated sleep paralysis without an incubus phenomenon. Based on the condition's robust clinical presentation and the relatively high prevalence rates, we advocate inclusion of the incubus phenomenon as a diagnostic category in major classifications such as the International Classification of Diseases and Related Health Problems and the Diagnostic and Statistical Manual of Mental Disorders. Recommendations are also made for clinical practice and future research.

Terror and bliss? Commonalities and distinctions between sleep paralysis, lucid dreaming, and their associations with waking life experiences

Sleep paralysis and lucid dreaming are both dissociated experiences related to rapid eye movement (REM) sleep. Anecdotal evidence suggests that episodes of sleep paralysis and lucid dreaming are related but different experiences. In this study we test this claim systematically for the first time in an online survey with 1928 participants (age range: 18–82 years; 53% female). Confirming anecdotal evidence, sleep paralysis and lucid dreaming frequency were related positively and this association was most apparent between lucid dreaming and sleep paralysis episodes featuring vestibular‐motor hallucinations. Dissociative experiences were the only common (positive) predictor of both sleep paralysis and lucid dreaming. Both experiences showed different associations with other key variables of interest: sleep paralysis was predicted by sleep quality, anxiety and life stress, whereas lucid dreaming was predicted by a positive constructive daydreaming style and vividness of sensory imagery. Overall, results suggest that dissociative experiences during wakefulness are reflected in dissociative experiences during REM sleep; while sleep paralysis is related primarily to issues of sleep quality and wellbeing, lucid dreaming may reflect a continuation of greater imaginative capacity and positive imagery in waking states.

A clinician's guide to recurrent isolated sleep paralysis

This review summarizes the empirical and clinical literature on sleep paralysis most relevant to practitioners. During episodes of sleep paralysis, the sufferer awakens to rapid eye movement sleep-based atonia combined with conscious awareness. This is usually a frightening event often accompanied by vivid, waking dreams (ie, hallucinations). When sleep paralysis occurs independently of narcolepsy and other medical conditions, it is termed "isolated" sleep paralysis. Although the more specific diagnostic syndrome of "recurrent isolated sleep paralysis" is a recognized sleep-wake disorder, it is not widely known to nonsleep specialists. This is likely due to the unusual nature of the condition, patient reluctance to disclose episodes for fear of embarrassment, and a lack of training during medical residencies and graduate education. In fact, a growing literature base has accrued on the prevalence, risk factors, and clinical impact of this condition, and a number of assessment instruments are currently available in both self-report and interview formats. After discussing these and providing suggestions for accurate diagnosis, differential diagnosis, and patient selection, the available treatment options are discussed. These consist of both pharmacological and psychotherapeutic interventions which, although promising, require more empirical support and larger, well-controlled trials.

Sleep Paralysis Among Egyptian College Students: Association With Anxiety Symptoms (PTSD, Trait Anxiety, Pathological Worry)

Among Egyptian college students in Cairo (n = 100), this study examined the relationship between sleep paralysis (SP) and anxiety symptoms, viz., posttraumatic stress disorder (PTSD), trait anxiety, and pathological worry. SP rates were high; 43% of participants reported at least one lifetime episode of SP, and 24% of those who reported at least one lifetime episode had experienced four or more episodes during the previous year. Fourteen percent of men had experienced SP as compared to 86% of women. As hypothesized, relative to non-SP experiencers, participants who had SP reported higher symptoms of PTSD, trait anxiety, and pathological worry. Also, as hypothesized, the experiencing of hypnogogic/hypnopompic hallucinations during SP, even after controlling for negative affect, was highly correlated with symptoms of PTSD and trait anxiety. The study also investigated possible mechanisms by examining the relationship of hallucinations to anxiety variables.

Rates and characteristics of sleep paralysis in the general population of Denmark and Egypt

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.

Lifetime prevalence rates of sleep paralysis: a systematic review

OBJECTIVE

To determine lifetime prevalence rates of sleep paralysis.

DATA SOURCES

Keyword term searches using "sleep paralysis", "isolated sleep paralysis", or "parasomnia not otherwise specified" were conducted using MEDLINE (1950-present) and PsychINFO (1872-present). English and Spanish language abstracts were reviewed, as were reference lists of identified articles.

STUDY SELECTION

Thirty five studies that reported lifetime sleep paralysis rates and described both the assessment procedures and sample utilized were selected.

DATA EXTRACTION

Weighted percentages were calculated for each study and, when possible, for each reported subsample.

DATA SYNTHESIS

Aggregating across studies (total N=36,533), 7.6% of the general population, 28.3% of students, and 31.9% of psychiatric patients experienced at least one episode of sleep paralysis. Of the psychiatric patients with panic disorder, 34.6% reported lifetime sleep paralysis. Results also suggested that minorities experience lifetime sleep paralysis at higher rates than Caucasians.

CONCLUSIONS

Sleep paralysis is relatively common in the general population and more frequent in students and psychiatric patients. Given these prevalence rates, sleep paralysis should be assessed more regularly and uniformly in order to determine its impact on individual functioning and better articulate its relation to psychiatric and other medical conditions.

Isolated sleep paralysis and fearful isolated sleep paralysis in outpatients with panic attacks

Isolated sleep paralysis (ISP) has received scant attention in clinical populations, and there has been little empirical consideration of the role of fear in ISP episodes. To facilitate research and clinical work in this area, the authors developed a reliable semistructured interview (the Fearful Isolated Sleep Paralysis Interview) to assess ISP and their proposed fearful ISP (FISP) episode criteria in 133 patients presenting for panic disorder treatment. Of these, 29.3% met lifetime ISP episode criteria, 20.3% met the authors' lifetime FISP episode criteria, and 12.8% met their recurrent FISP criteria. Both ISP and FISP were associated with minority status and comorbidity. However, only FISP was significantly associated with posttraumatic stress disorder, body mass, anxiety sensitivity, and mood and anxiety disorder symptomatology.

The assessment of the phenomenology of sleep paralysis: the Unusual Sleep Experiences Questionnaire (USEQ)

Previous research has found a relationship between sleep paralysis (SP) and anxiety states and higher rates have been reported among certain ethnic groups. To advance the cross-cultural study of SP, we developed a brief assessment instrument (which can be self-administered), the Unusual Sleep Experiences Questionnaire (USEQ). In this article, we report on a pilot study with the USEQ in a sample of 208 college students. The instrument was easily understood by the participants, with one quarter reporting at least one lifetime episode of SP. As in previous studies, SP was associated with anxiety (in particular, panic attacks).

Biological variations in depression and anxiety between East and West

Ethnicity and culture represent important factors in shaping psychopathology as well as pharmacotherapeutic responses in psychiatric patients. A large body of literature, accumulated over the past several decades, demonstrates that these factors not only determine the metabolism and disposition of medications (pharmacokinetics), but also their interactions with therapeutic targets (pharmacodynamics). This article focuses on the impact of such variations on the diagnosis and treatment of depression and anxiety disorders between East and West. Genes controlling the expression of drug metabolizing enzymes as well as the function of the brain are highly polymorphic, and the patterns and distribution of these polymorphisms are typically divergent across ethnic groups. To the extent that these genetic patterns determine drug response, ethnic variations in these genetic dispositions will lead to differential responses in clinical settings. In addition, the expression of these genes is significantly influenced by environmental factors including diet as well as exposure to other natural products. Superimposed on these biological influences, culturally determined beliefs and behavioral patterns also profoundly influence patients' expectations of treatment response, adherence, and interactions with clinicians. In addition to pharmacotherapeutic responses, emerging data also indicate that significant ethnic variations exist in genetic polymorphisms and neurobiologic correlates (biomarkers) that may be associated with the vulnerability to psychiatric disorders. These considerations argue for the importance of examining biological variations across ethnic groups, especially in the clinical context, in terms of the assessment and treatment of psychiatric patients, and in our understanding of psychiatric phenomenology and nosology.

Lifetime prevalence and incidence of parasomnias in a population of young adult Nigerians

Lifetime prevalence, incidence, and risk factors for parasomnias were determined. Past experiences of non-REM, REM, and sleep-transition parasomnias were recorded. Diaries of night sleep duration, parasomnias, perception of aliens, levels of physical activity, headaches and intake of all substances, drugs, and tobacco were kept for 14 consecutive days. A total of 276 subjects were studied. Lifetime prevalences (95% CI) were 725 (668-776) for occurrence of any parasomnia, 43 (25-74) for sleepwalking, 112 (80-155) for sleep terror, 475 (416-533) for nightmares, 225 (179-277) for sleep paralysis, 43 (25-74) for sleep starts, 322 (270-380) for sleep talking, and 344 (291-402) for enuresis. Incidences (95% CI) were 210 (166-262) for occurrence of any parasomnia, 14 (6-37) for sleepwalking, 11 (4-31) for sleep terror, 170 (131-219) for confusional arousal, 18 (8-42) for nightmares, 14 (6-37) for sleep paralysis, 33 (17-61) for sleep starts, and 4 (1-20) for sleep enuresis. Multivariate analysis showed associations of increase occurrence of parasomnias and duration of sleep >7 h (p < 0.05) and intake of alcohol (p < 0.001), but heavy workload before sleep was associated with decreased occurrence of parasomnias (p < 0.01). Gender, smoking, caffeinated drinks, hypnotics, and headaches were not associated with parasomnias. Incidence of presence of aliens (95% CI) in the room was 25(0/infinity) (12-51). This study shows that more than 70% of the population have experienced parasomnias at any time in the past. Nightmares, enuresis, sleep paralysis and night terrors are the commonest parasomnias experienced in the past, while confusional arousal, sleep starts, and nightmares are the commonest parasomnias currently experienced. Incidence estimates show that all parasomnias persist into adulthood at reduced rates, but reduction of occurrence was greatest for enuresis. Long duration of night sleep and intake of alcohol predisposed subjects to higher occurrence of parasomnias.

Temporal relations between sleep problems and both traumatic event exposure and PTSD: a critical review of the empirical literature

There has been growing interest in the interrelations among traumatic event exposure, posttraumatic stress disorder (PTSD), and sleep problems. A wealth of research has examined the associations among these factors and there is an emerging literature focused on how sleep problems relate to both traumatic event exposure and PTSD across time. The current review provides a detailed analysis of studies pertaining to the temporal patterning of sleep problems and traumatic event-related factors (e.g., traumatic event exposure, PTSD) and draws conclusions regarding the current state of this literature. Research coalesces to suggest (1) exposure to a traumatic event can interfere with sleep, (2) PTSD is related to the development of self-reported sleep problems, but evidence is less clear regarding objective indices of sleep, and (3) limited evidence suggests sleep problems may interfere with recovery from elevated posttraumatic stress levels. Future research now needs to focus on understanding mechanisms involved in these patterns to inform the prevention and treatment of comorbid sleep problems and PTSD.