Recurrent Isolated Sleep Paralysis.

Recurrent isolated sleep paralysis has a 7.6% lifetime prevalence of at least one episode in the general population. Episodes resolve spontaneously and are benign. Sleep paralysis represents a dissociate state, with persistence of the rapid eye movement (REM)-sleep muscle atonia in the waking state. The intrusion of alpha electroencephalogram into REM sleep is followed by an arousal response and then by persistence of REM atonia into wakefulness. Predisposing factors include irregular sleep-wake schedules, sleep deprivation, and jetlag. No drug treatment is required. Patients should be informed about sleep hygiene. Cognitive behavioral therapy may be useful in cases accompanied by anxiety and frightening hallucinations.

Prevalence, incidence, evolution and associated factors of sleep paralysis in a longitudinal study of the US general population.

BACKGROUND AND OBJECTIVE: Sleep paralysis is a common phenomenon which causes and consequences are seldomly studied. The aim of this study was to investigate the incidence and prevalence of sleep paralysis (SP) in the American adult population and its evolution on a 3-year period. METHODS: This longitudinal study was conducted between 2002 and 2015 and included a representative sample of the US general population. A total of 12,218 subjects were initially interviewed (W1) and 10,931 were re-interviewed three years later (W2). The subjects participated in telephone interviews using the Sleep-EVAL expert system. Each interview lasted for about 1 h. SP episodes were assessed according to their frequency and duration. RESULTS: At W1, 9.7% (95%CI: 9.1%-10.3%) reported having ≥1 episode of SP in the previous year. At W2, 15.1% (95%CI: 14.4%-15.8%) reported SP. A total of 29.9% of subjects with SP at W1 still reported episodes at W2. The 1-year incidence was 2.7% (95%CI: 2.4-3.0%). After adjusting for age and sex, prevalent SP (i.e., present at W2) was predicted by age and race and the following factors present at W1: major depressive disorder, pain, hypersomnolence, cataplexy, hypnagogic and hypnopompic hallucinations, posttraumatic stress disorder, a reduction in sleep duration of ≥60 min, and the use of analgesic/antipyretic medication. Incident SP (i.e. new cases at W2) had similar predictive factors. DISCUSSION: Episodes of SP are frequent in the general population. Its persistence is predicted by several factors associated with narcolepsy like hypersomnolence and cataplexy but also by other factors like posttraumatic stress disorder or pain.

Characteristics of Sleep Paralysis and Its Association with Anxiety Symptoms, Perceived Stress, PTSD, and Other Variables Related to Lifestyle in Selected High Stress Exposed Professions.

Sleep paralysis (SP) is a hypnagogic or hypnopompic state associated with the inability to move while conscious. Recurrent isolated sleep paralysis (RISP) is a type of REM parasomnia. Individuals experiencing anxiety disorders, PTSD, exposure to chronic stress, or shift work are at risk of developing this sleep disorder. This study aimed to assess: (1) the prevalence, frequency, and symptomatology of SP, and (2) the impact of the severity of anxiety symptoms, perceived stress, and lifestyle mode variables on the frequency and severity of SP in four professional groups at high risk of SP (n = 844): nurses and midwives (n = 172), policemen (n = 174), teachers (n = 107), and a group of mixed professions-"other professions" (n = 391). The study used a battery of online questionnaires: the Sociodemographic and Health Status Questionnaire, the SP-EPQ, the PCL -5, the STAI-T, the PSWQ and the PSS-10. The prevalence of SP was the lowest among policemen (15.5%) and the highest in the group of "other professions" (39.4%). The association of SP with symptoms of PTSD and anxiety was confirmed in the group of nurses and "other professions". Among other factors modulating the incidence and severity of SP were: age, BMI, smoking, alcohol consumption, sleep duration, and perceived stress. This study indicates that there exist links between SP and psychological and lifestyle factors, suggesting a complex etiology for this sleep disorder. Due to the high prevalence of SP in the studied groups of occupations, further research is necessary to develop preventive and therapeutic methods for SP.

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.

Predictors of sleep paralysis and relationship of sleep paralysis with sleep quality in university students of Islamabad.

OBJECTIVE: To determine the frequency of sleep paralysis among university students, and to determine the association between sleep paralysis and sleep quality along with different predictive factors leading to sleep paralysis. METHODS: The descriptive cross-sectional study was conducted at the National University of Modern Languages, Islamabad, Pakistan, from June to October, 2019, and comprised adult students of either gender who had experienced at least one episode of sleep paralysis in the past. Demographic variables were obtained using Google Form, while experiences of sleep paralysis were assessed using the Waterloo Unusual Sleep Experience Questionnaire, and sleep quality was assessed with the Sleep Condition Indicator. Data was analysed using SPSS 20. RESULTS: Initially, 440 students were assessed/ Of them, 233(53%) were males, 207(47%) were females, 208(47.3%) were aged 20-23 years, and 129(29.3%) were studying in the third year of their university programme. Of the total, 130(29.5%) subjects had experienced sleep paralysis at least once in their lifetime. The most frequent sensation experienced was feeling of floating 22(16.9%). Mean age at the time of the first experience was 9.7±3.1 years, and 66(50.8%) had experienced the episodes while lying on their back, while 32(24.6%) had positive family history of sleep paralysis. Sleep paralysis had significant relationship with sleep quality (p<0.001). CONCLUSIONS: About one-third of the sample had experienced sleep paralysis once in their lifetime. The relationship between sleep paralysis and insomnia was significant.

Sleep paralysis in college students.

Objective: We examined the prevalence of sleep paralysis (SP), its association with stress and sleep, and associated subjective experiences and beliefs. Participants: 1,115 college students from a large university in the southwestern United States. The sample was predominantly Hispanic (94%) and female (70%). Methods: Validated measures of life-events stress, self-perceived stress, sleep quality and insomnia were administered to participants online. Results: 35% of students had previously experienced SP and reported greater stress and poorer sleep than those who had never experienced it. Effect sizes were larger when comparing those who had/had not experienced SP within the prior year. Conclusions: Based on our predominantly Hispanic and majority female sample, we found that SP is experienced by approximately one-third of undergraduate students and associated with both higher stress and poorer sleep. We therefore recommend that college health practitioners seek ways to integrate relevant assessment and education into campus health practices.

A German online survey of people who have experienced sleep paralysis.

We present some key findings from an online survey on isolated sleep paralysis. The aim of our study was to get a differentiated picture of the correlation between the frequency of sleep paralysis and several phenomena (symptoms, experiences) as well as factors correlated with these phenomena. We also investigated the role of gender in relation to the experience of sleep paralysis. We used a selected sample of subjects who had had at least one sleep paralysis experience, with a total of 380 subjects. On average, the participants experienced 10-20 sleep paralysis episodes. We found high and expected positive correlations between the frequency of sleep paralysis experiences and the amount of phenomena, emotions, and perceived shapes and forms experienced during sleep paralysis. An increased frequency of sleep paralysis also appears to lead to habituation and de-dramatization in some affected individuals. Interestingly, significant correlations are missing where one would have suspected them based on the previous hypotheses. Neither self-perceived general stress nor poor sleep hygiene appeared to influence the frequency of sleep paralysis. We found highly significant gender differences in some items. Women reported more experienced phenomena and emotions overall, had more frequent sleep paralysis experiences of the intruder and incubus type, and were significantly more likely to perceive concrete forms such as human figures or people they know. They were also more likely than men to report experiencing fearful emotions, especially the fear of going crazy. Most of these findings were based on exploratory questions; they require replication for validation.

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.

Could sleep paralysis be pleasant?

Sleep paralysis is an inability to move at sleep onset or upon awakening. It is often a distressing experience that can be associated with significant clinical consequences. Few studies have focussed on pleasant sleep paralysis episodes. The present study aimed to determine the relative prevalence of pleasant episodes of sleep paralysis as well as variables that may make them more likely to occur. Participants (N = 172) with recurrent episodes of sleep paralysis completed a battery of questionnaires investigating sleep paralysis episodes, trauma symptoms, life satisfaction, and Big Five personality traits. Pleasant sleep paralysis was found to be a fairly common experience (i.e. 23%). Episodes were emotionally complex, with pleasant episodes often involving some admixture of fear. In terms of hallucinations, pleasant episodes were more likely to involve vestibular-motor sensations (i.e. illusory body movements) and some individuals reported an ability to induce these hallucinations. Contrary to expectation, neither lower trauma symptomatology nor higher levels of reported life satisfaction predicted pleasant sleep paralysis. However, the ability to lucid dream and higher levels of trait openness to new experiences appeared to make pleasant episodes more likely. Clinical implications are discussed.

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.

Sleepwalking and Sleep Paralysis: Prevalence in Colombian Families With Genetic Generalized Epilepsy.

BACKGROUND: Sleep deprivation commonly increases seizure frequency in patients with genetic generalized epilepsy, though it is unknown whether there is an increased prevalence of sleepwalking or sleep paralysis in genetic generalized epilepsy patients. Establishing this could provide insights into the bio-mechanisms or genetic architecture of both disorders. The aim of this study was to determine the prevalence of sleepwalking and sleep paralysis in a cohort of patients with genetic generalized epilepsy and their relatives in extended families. METHODS: A structured interview based on International League Against Epilepsy (ILAE) and International Classification of Sleep Disorders (ICSD-3) criteria was applied to 67 index cases and their relatives to determine genetic generalized epilepsy subtypes and assess the occurrence of sleepwalking or sleep paralysis. Bivariate analysis was performed using chi-square and Fisher exact tests. RESULTS: The prevalence of sleepwalking and sleep paralysis was 15.3% (95% confidence interval 12.1-18.9) and 11.7% (95% confidence interval 8.7-15.3), respectively. Unusually, no sleepwalkers were found among individuals displaying epilepsy with generalized tonic-clonic seizures. Approximately a quarter of the patients had either parasomnia or genetic generalized epilepsy. Over half the genetic generalized epilepsy families had at least 1 individual with sleepwalking, and more than 40% of the families had one individual with sleep paralysis. CONCLUSION: The prevalence of sleepwalking or sleep paralysis is reported for individuals with genetic generalized epilepsy and their relatives. The co-existence of either parasomnia in the genetic generalized epilepsy patients and the co-aggregation within their families let suggest that shared heritability and pathophysiological mechanisms exist between these disorders. We hypothesize that sleepwalking/sleep paralysis and genetic generalized epilepsy could be variable expression of genes in shared pathways.

Subjective sleep-related variables in those who have and have not experienced sleep paralysis.

Research suggests that poor sleep quality is related to the occurrence of sleep paralysis, although the precise relationship between these two variables is unknown. This association has generated interest due to the related possibility that improving sleep quality could help to combat episodes of sleep paralysis. To date, studies examining the association between sleep quality and sleep paralysis have typically measured sleep quality using general measures such as the global score of the Pittsburgh Sleep Quality Index (PSQI). The aim of this study was to increase the precision of our understanding of the relationship between sleep paralysis and other aspects of sleep by investigating associations between different sleep-related variables and sleep paralysis. Using data from the G1219 twin/sibling study, analyses were performed on 860 individuals aged 22-32 years (66% female). Results showed that two components of the PSQI, sleep latency and daytime dysfunction, were predictors of sleep paralysis. In addition, a number of other sleep-related variables were related significantly to sleep paralysis. These were: insomnia symptoms, sleep problems commonly related to traumatic experiences, presleep arousal, cognitions about sleep and excessive daytime sleepiness. There was no relationship with sleep-disordered breathing, diurnal preference or sleeping arrangements. Potential mechanisms underlying these results and suggestions for future research are discussed.

A systematic review of variables associated with sleep paralysis.

Sleep paralysis is a relatively common but under-researched phenomenon. While the causes are unknown, a number of studies have investigated potential risk factors. In this article, we conducted a systematic review on the available literature regarding variables associated with both the frequency and intensity of sleep paralysis episodes. A total of 42 studies met the inclusion criteria. For each study, sample size, study site, sex and age of participants, sleep paralysis measure, and results of analyses looking at the relationship(s) between sleep paralysis and associated variable(s) were extracted. A large number of variables were associated with sleep paralysis and a number of themes emerged. These were: substance use, stress and trauma, genetic influences, physical illness, personality, intelligence, anomalous beliefs, sleep problems and disorders (both in terms of subjective sleep quality and objective sleep disruption), symptoms of psychiatric illness in non-clinical samples (particularly anxiety symptoms), and psychiatric disorders. Sleep paralysis appears to be particularly prevalent in post-traumatic stress disorder, and to a less degree, panic disorder. Limitations of the current literature, directions for future research, and implications for clinical practice are discussed.

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.

Frequencies and Associations of Narcolepsy-Related Symptoms: A Cross-Sectional Study.

OBJECTIVES: Narcolepsy is a disabling disease with a delayed diagnosis. At least 3 years before the disorder identification, several comorbidities can be observed in patients with narcolepsy. The early recognition of narcolepsy symptoms may improve long-term prognosis of the patients. Thus, we aimed to investigate the prevalence of the symptoms associated with narcolepsy and its social and psychological association in a sample of Sao Paulo city inhabitants. METHODS: We performed a cross-sectional evaluation with 1,008 individuals from the Sao Paulo Epidemiologic Sleep Study (EPISONO). Excessive daytime sleepiness (EDS) was assessed by the Epworth Sleepiness Scale. Volunteers were also asked about the occurrence of cataplectic-like, hypnagogic or hypnopompic hallucinations, and sleep paralysis symptoms. The participants underwent a full-night polysomnography and completed questionnaires about psychological, demographic, and quality of life parameters. RESULTS: We observed a prevalence of 39.2% of EDS, 15.0% of cataplectic-like symptom, 9.2% of hypnagogic or hypnopompic hallucinations, and 14.9% of sleep paralysis in Sao Paulo city inhabitants. A frequency of 6.9% was observed when EDS and cataplectic-like symptoms were grouped. The other associations were EDS + hallucinations (4.7%) and EDS + sleep paralysis (7.5%). Symptomatic participants were predominantly women and younger compared with patients without any narcolepsy symptom (n = 451). Narcolepsy symptomatology was also associated with a poor quality of life and symptoms of depression, anxiety, and fatigue. CONCLUSIONS: Narcolepsy-related symptoms are associated with poor quality of life and worse psychological parameters.

A twin and molecular genetics study of sleep paralysis and associated factors.

Sleep paralysis is a relatively common but under-researched phenomenon. In this paper we examine prevalence in a UK sample and associations with candidate risk factors. This is the first study to investigate the heritability of sleep paralysis in a twin sample and to explore genetic associations between sleep paralysis and a number of circadian expressed single nucleotide polymorphisms. Analyses are based on data from the Genesis1219 twin/sibling study, a community sample of twins/siblings from England and Wales. In total, data from 862 participants aged 22-32 years (34% male) were used in the study. This sample consisted of monozygotic and dizygotic twins and siblings. It was found that self-reports of general sleep quality, anxiety symptoms and exposure to threatening events were all associated independently with sleep paralysis. There was moderate genetic influence on sleep paralysis (53%). Polymorphisms in the PER2 gene were associated with sleep paralysis in additive and dominant models of inheritance-although significance was not reached once a Bonferroni correction was applied. It is concluded that factors associated with disrupted sleep cycles appear to be associated with sleep paralysis. In this sample of young adults, sleep paralysis was moderately heritable. Future work should examine specific polymorphisms associated with differences in circadian rhythms and sleep homeostasis further in association with sleep paralysis.

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.

Hallucinations in narcolepsy with and without cataplexy: contrasts with Parkinson's disease.

BACKGROUND: Narcolepsy and Parkinson's disease (PD) are associated with hallucinations, excessive daytime sleepiness, REM sleep behavior disorder (RBD), as well as complete (narcolepsy with cataplexy) vs. partial (PD, narcolepsy without cataplexy) hypocretin-1 deficiency. OBJECTIVE: To compare the hallucinations associated with narcolepsy to those of PD. METHODS: One hundred patients with narcolepsy (with and without cataplexy) and 100 patients with PD were consecutively interviewed about their hallucinations (frequency, phenomenology, insight into unreality and association with sleep) as well as their risk factors. RESULTS: Hallucinations occurred more frequently and with more motor and multimodal aspects in narcolepsy with cataplexy (59%) than in narcolepsy without cataplexy (28%) and PD (26%). Compared to PD, the hallucinations in narcolepsy were less frequently of the passage/presence type (passage: brief visions of a person or animal passing sideways; presence: perception that a living character or an animal is behind or near the subject, without the subject actually seeing, hearing or touching it), more frequently auditory and more often associated with sleep. However, in 40% of the patients with narcolepsy and 54% of the patients with PD, the hallucinations occurred while the patients were wide awake. Patients with cataplexy had reduced immediate insight into the unreality of their hallucinations compared to patients with PD, but the delusions were exceptional (2%), transient and based on hallucinations in both groups. The risk factors for hallucinations were sleep paralysis and RBD in narcolepsy and motor disability and sleepiness in PD. CONCLUSIONS: The multimodal, dreamlike aspect of hallucinations in narcolepsy with cataplexy could transiently impair the patients' insight. The high frequency of these hallucinations (compared to those in narcolepsy without cataplexy or PD) suggests that complete (more than partial) hypocretin-1 deficiency promotes hallucinations.

Nightmare and sleep paralysis among Japanese adolescents: a nationwide representative survey.

OBJECTIVE: The objective of this study was to clarify the prevalence of nightmares and sleep paralysis and associated factors among Japanese adolescents. METHODS: This study was designed as a cross-sectional sampling survey. The targets were junior and senior high schools throughout Japan. Self-reported anonymous questionnaires were sent to schools for all students to complete. RESULTS: A total of 90,081 questionnaires were analyzed. The overall response rate was 62.6%, and the prevalence of nightmares and sleep paralysis was 35.2% and 8.3%, respectively. Multiple logistic analyses revealed that female sex, drinking alcohol, poor mental health, difficulty initiating sleep, low subjective sleep assessment, presence of excessive daytime sleepiness, and presence of sleep paralysis had higher odds ratios than others for nightmares. Male sex, poor mental health, drinking alcohol, taking a long daytime nap, early or late bedtime, difficulty initiating sleep, low subjective sleep assessment, presence of excessive daytime sleepiness, and presence of nightmares had higher odds ratios than other factors for sleep paralysis. CONCLUSIONS: This study has revealed the prevalence of nightmares and sleep paralysis among Japanese adolescents. Furthermore, the results of this study suggest that it is important to maintain regular sleep habits for preventing these symptoms. We propose that health education about regular sleep habits should be promoted among Japanese adolescents.