Sleep Medicine Reviews
June 8, 2017
Dan Denis, Christopher C. French, Alice M. Gregory
129 citations
Sleep paralysis is a common but poorly understood phenomenon. A systematic review of 42 studies identified multiple variables associated with its frequency and intensity, including substance use, stress and trauma, genetic influences, physical illness, personality, intelligence, anomalous beliefs, sleep problems and disorders, and psychiatric symptoms. Sleep paralysis is especially prevalent in post-traumatic stress disorder and, to a lesser degree, panic disorder. The review notes limitations in the current literature and suggests directions for future research and clinical practice.
Journal of Sleep Research
July 27, 2016
Dan Denis, Giulia Poerio
70 citations
Sleep paralysis and lucid dreaming are both dissociated states linked to REM sleep. A survey of 1928 adults (ages 18–82, 53% female) found that more frequent lucid dreaming is associated with more frequent sleep paralysis, especially episodes involving vestibular-motor hallucinations. Dissociative experiences during wakefulness predicted both phenomena. However, sleep paralysis was predicted by poor sleep quality, anxiety, and life stress, whereas lucid dreaming was predicted by a tendency toward positive, constructive daydreaming and vivid sensory imagery. The findings suggest that dissociative tendencies during wakefulness extend into REM sleep, but sleep paralysis reflects sleep and well-being issues, while lucid dreaming may stem from greater imaginative capacity and positive imagery in waking life.
Sleep
December 13, 2018
Dan Denis, Giulia Poerio, Sarah Derveeuw et al.
25 citations
Exploding head syndrome, a sensory parasomnia where people perceive loud noises or a sense of explosion when falling asleep or waking, affects about 10-15% of individuals, with significant fear in some cases. Across two samples—199 female undergraduates and 1,683 international participants aged 18-82—lifetime prevalence was 37.19% and 29.59%, respectively, with monthly episodes in 6.54% and 3.89%. Insomnia symptoms and sleep paralysis frequency were consistently linked to the condition in multiple logistic regression models. In the larger sample, dissociative experiences during wakefulness and nightmares also showed associations. These findings offer initial insights into factors related to exploding head syndrome.
Journal of Sleep Research
August 1, 2023
Betul Rauf, Rotem Perach, Juan J Madrid-Valero et al.
8 citations
Poor sleep quality significantly correlates with stronger beliefs in paranormal phenomena. In a survey of 8,853 participants, those experiencing insomnia, longer sleep latency, and shorter sleep duration were more likely to believe in concepts like ghosts (62%), the soul living on after death (58%), and alien encounters (45%). Additionally, episodes of exploding head syndrome and isolated sleep paralysis were linked to beliefs in aliens visiting Earth. These findings highlight the complex relationship between sleep disturbances and anomalistic experiences, suggesting avenues for enhanced psychoeducation on sleep health.
Frontiers in Sleep
May 28, 2024
Lucas Bellaiche, Adam Haar Horowitz, Mason McClay et al.
5 citations
Hypnagogia, the transition from wakefulness to sleep, involves dreams that forge connections among unrelated concepts, potentially boosting creativity, learning, and memory. Mind-wandering, a form of spontaneous thought, may rely on similar processes. This study tested a new tool called Dormio Light to cue and index hypnagogic dream content remotely, cheaply, and quickly. In 80 participants (34 female), the tool successfully cued specific thought content (e.g., a tree) during hypnagogia and mind-wandering, with incubation rates matching lab studies. Phenomenological differences emerged between the two states. The tool offers a practical way to study these cognitive states and their relationship.
British journal of psychology (London, England : 1953)
November 1, 2023
Betul Rauf, Rotem Perach, Juan J Madrid-Valero et al.
5 citations
Sleep disturbances such as sleep paralysis, lucid dreams, nightmares, and hypnagogic hallucinations are positively associated with reports of paranormal experiences and beliefs, including those involving ghosts, spirits, and near-death experiences. A scoping review of 44 cross-sectional studies found consistent links between these sleep variables and ostensibly paranormal phenomena. The findings suggest that nighttime experiences many people interpret as supernatural may stem from common sleep disruptions. This has clinical implications, such as reducing misdiagnosis and guiding treatment for sleep-related experiences.
Sleep Medicine
April 1, 2023
Betul Rauf, Brian A Sharpless, Dan Denis et al.
Isolated sleep paralysis (ISP) is a benign but frightening condition involving temporary inability to move at sleep onset or upon awakening. In an online survey of 6,811 participants (mean age 46.9, 66.1% female), those who had experienced at least one lifetime ISP episode reported longer sleep onset latencies, shorter sleep duration, and greater insomnia symptoms than those without ISP. Females and younger participants were more likely to experience ISP. Significant fear during episodes was reported by 76.0% of participants. Most (63.3%) attributed ISP to 'something in the brain,' while 7.1% endorsed supernatural causes. Five prevention strategies (e.g., changing sleep position, adjusting sleep patterns) showed at least 60.0% effectiveness, and five disruption strategies (e.g., physical/bodily action, making noise) ranged from 29.5% to 61.8% effectiveness.
Journal of Sleep Research
October 1, 2018
Dan Denis, Christopher C. French, Melanie N. Schneider et al.
Poor sleep quality is linked to sleep paralysis, but the precise nature of the relationship is unclear. This study analyzed data from 860 individuals aged 22–32 years (66% female) from the G1219 twin/sibling study. Two components of the Pittsburgh Sleep Quality Index—sleep latency and daytime dysfunction—predicted sleep paralysis. Additional factors associated with sleep paralysis included insomnia symptoms, sleep problems related to traumatic experiences, presleep arousal, unhelpful thoughts about sleep, and excessive daytime sleepiness. No relationship was found with sleep-disordered breathing, diurnal preference, or sleeping arrangements. The results suggest that improving specific aspects of sleep quality might help reduce sleep paralysis episodes.
Nature and Science of Sleep
January 1, 2018
Dan Denis
Sleep paralysis is the experience of waking up unable to move, often accompanied by extreme fear and, in some cases, significant distress. This review of existing literature found that worse subjective sleep quality is consistently associated with higher odds of sleep paralysis. Insomnia symptoms, but not a diagnosed insomnia disorder, also predict its occurrence. Sleep paralysis is linked to other unusual sleep experiences like nightmares, exploding head syndrome, and lucid dreaming. Objective laboratory recordings show sleep paralysis is a mixed state of consciousness, combining elements of rapid eye movement sleep with wakefulness. Future research should use longitudinal designs and broader assessments to better understand the condition.
Unusual and Rare Psychological Disorders
November 1, 2016
Brian A Sharpless, Dan Denis
Isolated sleep paralysis is a common phenomenon where aspects of REM sleep, such as muscle atonia and dream activity, occur while awake, often causing terror. It has influenced supernatural and folkloric beliefs. Rates are higher among students and psychiatric patients, and a minority experience clinically significant distress or interference. Although assessment and treatment options exist, large-scale efficacy trials have not yet been conducted.
Journal of Sleep Research
February 9, 2015
Dan Denis, C. French, R. Rowe et al.
Sleep paralysis is moderately heritable (53%) in a UK sample of 862 twins and siblings aged 22–32 years. Poor sleep quality, anxiety symptoms, and exposure to threatening events were each independently associated with sleep paralysis. Variants in the PER2 gene showed some association, but this did not survive correction for multiple testing. The authors conclude that factors disrupting sleep cycles appear linked to sleep paralysis and that future research should explore circadian-rhythm and sleep-homeostasis polymorphisms.