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Sleep paralysis

Sleep paralysis is a parasomnia disorder characterized by a temporary inability to move, speak, or react while transitioning between wakefulness and sleep, particularly during rapid eye movement (REM) sleep, despite remaining conscious.^[1] Episodes typically last from several seconds to a few minutes and often involve sensations of chest pressure, suffocation, or vivid hallucinations, such as sensing an intruder or experiencing out-of-body feelings, which can provoke intense fear or panic.^[2] Although generally benign and self-resolving, recurrent episodes may disrupt sleep quality and contribute to daytime fatigue.^[3] The condition arises from a dissociation in the sleep-wake cycle, where the brain awakens but the body's natural muscle atonia—intended to prevent acting out dreams during REM sleep—persists into consciousness.^[2] Common triggers include sleep deprivation, irregular sleep schedules (such as those experienced by shift workers), high levels of stress or anxiety, and sleeping in a supine position.^[3] It is frequently associated with other sleep disorders like narcolepsy, though it can occur in isolation without underlying pathology.^[1] Prevalence varies by population, with approximately 7.6% of individuals experiencing recurrent sleep paralysis and up to 30% reporting at least one episode in their lifetime; it is slightly more common in females, young adults aged 20 to 30, and those with psychiatric conditions or a family history.^[2] Risk factors also encompass substance use, such as alcohol or certain medications, and posttraumatic stress disorder.^[2] Diagnosis relies on clinical history, sleep diaries, and sometimes polysomnography to rule out related disorders, while treatment focuses on improving sleep hygiene—such as maintaining a consistent schedule and reducing stimulants—rather than direct intervention for isolated cases.^[1] In severe or frequent instances, low-dose antidepressants or cognitive behavioral therapy may alleviate symptoms by addressing underlying anxiety.^[3]

Overview

Definition

Sleep paralysis is a temporary inability to move or speak that occurs during the transition between wakefulness and sleep, specifically when consciousness returns while the muscle atonia associated with rapid eye movement (REM) sleep persists.^[2] This phenomenon typically lasts from a few seconds to several minutes and can happen either as a person is falling asleep (hypnagogic) or waking up (hypnopompic).^[4] It arises due to a dissociation between the brain's wakeful state and the ongoing REM-related paralysis that normally prevents acting out dreams.^[5] The modern clinical understanding emerged in the 20th century through sleep medicine research, defining it as a parasomnia characterized by preserved REM atonia encroaching into partial wakefulness without other neurological deficits.^[6]

Relation to Sleep Stages

Sleep occurs in cycles that alternate between non-rapid eye movement (non-REM) sleep, consisting of three stages characterized by progressively deeper relaxation and slower brain waves, and rapid eye movement (REM) sleep, a later stage marked by heightened brain activity resembling wakefulness, rapid eye movements, and vivid dreaming.^[2] During REM sleep, the body enters a state of muscle atonia—a temporary paralysis of most voluntary muscles—mediated by inhibitory signals from the brainstem, specifically involving neurons in the sublaterodorsal nucleus that release glycine and GABA to suppress motor activity and prevent individuals from physically acting out their dreams.^[7] This atonia is a protective mechanism essential for normal REM sleep physiology.^[8] Sleep paralysis arises as a dissociative phenomenon during the transition between sleep stages, particularly when the muscle atonia of REM sleep persists into a state of partial or full wakefulness, resulting in conscious awareness without the ability to move or speak.^[2] This incomplete transition often occurs due to dysregulation in the brainstem mechanisms that normally deactivate atonia upon awakening, leading to a mismatch where the mind emerges from sleep while the body remains immobilized.^[9] Episodes are typically brief, lasting seconds to minutes, and reflect an overlap between REM sleep processes and wakeful consciousness.^[10] Such events most commonly occur during the hypnopompic phase upon awakening from REM sleep, though they can also happen during the hypnagogic phase at sleep onset, particularly in conditions like narcolepsy.^[11] Hypnagogic occurrences may involve rapid entry into REM sleep, while hypnopompic episodes align with the natural conclusion of REM stages, where arousal interrupts the full dissipation of atonia.^[12] It is fundamentally tied to disruptions in REM-related transitions within the overall sleep architecture.^[13]

Symptoms

Physical Sensations

The hallmark physical sensation of sleep paralysis is a profound inability to move voluntary muscles, while remaining fully conscious, with only eye movements and breathing preserved; this atonia persists from REM sleep into wakefulness and typically lasts from several seconds to a couple of minutes.^[14] This immobility occurs during transitions between REM sleep and wakefulness, reflecting a mismatch in the timing of neural reactivation.^[2] Common accompanying bodily experiences include a sensation of intense pressure on the chest or throat, often perceived as a heavy weight restricting movement, alongside feelings of suffocation due to irregular respiration and reduced activity in respiratory muscles.^[2]^[15] Some individuals report a physical sense of levitation or floating, classified as an illusory bodily movement experience that can occur in up to 30.8% of episodes.^[16] Autonomic responses during these episodes frequently involve heightened sympathetic nervous system activity, manifesting as tachycardia, elevated blood pressure, sweating, and an adrenaline surge triggered by the associated distress.^[14] These physiological changes contribute to the overall intensity of the experience but resolve as muscle control returns.^[2]

Perceptual Experiences

During episodes of sleep paralysis, individuals often experience vivid hallucinations that contribute significantly to the distress of the event. These perceptual experiences are categorized into three primary types: intruder, incubus, and vestibular-motor hallucinations. Intruder hallucinations typically involve a sense of a threatening presence in the room, accompanied by auditory perceptions such as footsteps or whispers, and visual illusions of shadowy figures or intruders approaching the bed.^[17] Incubus hallucinations manifest as intense pressure on the chest or throat, often interpreted as an entity sitting or lying on the body, leading to sensations of suffocation or impending doom.^[17] Vestibular-motor hallucinations, in contrast, include sensations of floating above the body, out-of-body experiences, or illusory movements like spinning or falling, which can feel disorienting but are sometimes less fear-inducing than the other types.^[18] Hallucinations occur in up to 75% of sleep paralysis episodes, rendering them a common feature that heightens the overall intensity of the experience.^[17] These perceptions are frequently multisensory and hyper-realistic, blending elements of dream content with wakeful awareness, which amplifies their terrifying quality for many individuals. The physical immobility during these episodes can exacerbate the fear, as the inability to move or respond intensifies the sense of vulnerability to the perceived threats.^[2] The psychological impact of these perceptual experiences is profound, with immediate terror reported in 80-90% of episodes, often evoking panic and a profound sense of helplessness.^[17] Recurrent hallucinations are associated with elevated anxiety levels, potentially contributing to the development or exacerbation of anxiety disorders over time, particularly in those with frequent occurrences.^[2] This emotional aftermath underscores the need for recognition of sleep paralysis as a factor in broader mental health concerns.^[18]

Pathophysiology

Neurological Basis

Sleep paralysis involves a disruption in the normal neural control of muscle tone during transitions between sleep and wakefulness, specifically tied to the persistence of rapid eye movement (REM) sleep mechanisms. In REM sleep, muscle atonia is primarily mediated by the sublaterodorsal nucleus (SLD) in the brainstem, a key region that activates inhibitory pathways to prevent motor activity during dreaming. The SLD, located in the pons, consists of glutamatergic neurons that project to the ventral medullary reticular formation, triggering the release of glycine and gamma-aminobutyric acid (GABA) onto spinal and cranial motor neurons, thereby hyperpolarizing them and inducing profound muscle paralysis.^[10]^[7] This atonia is normally deactivated upon arousal from REM sleep through the coordinated activity of brainstem arousal systems, but in sleep paralysis, dysregulation occurs when these systems fail to fully disengage the REM state. Specifically, incomplete inactivation of the locus coeruleus, a noradrenergic nucleus in the pons that promotes wakefulness and inhibits REM sleep, can lead to a persistence of atonia as consciousness emerges. Other arousal nuclei, such as those in the pedunculopontine and laterodorsal tegmental areas, may also contribute to this mismatch by not sufficiently suppressing REM-related inhibition during the sleep-wake transition.^[10]^[14] Polysomnographic studies provide evidence for this neurological overlap, revealing EEG patterns during sleep paralysis episodes that blend characteristics of REM sleep and wakefulness. These include sustained theta waves (4-8 Hz) indicative of REM activity alongside increased alpha waves (8-12 Hz) associated with partial arousal, creating a mixed spectral profile that reflects the hybrid state of consciousness. Such findings underscore the failure of neural circuits to resolve the boundary between REM inhibition and wakeful motor control.^[19]^[14]

Associated Brain Activity

Electroencephalography (EEG) studies have provided evidence of distinct brain activity patterns during sleep paralysis episodes, particularly in relation to fear responses and hallucinatory experiences. Overactivation of the amygdala has been proposed to contribute to the intense fear and emotional arousal commonly reported during episodes. Reduced activation in the prefrontal cortex has also been hypothesized to diminish top-down inhibitory control, potentially allowing unchecked propagation of hallucinatory content from subcortical regions. EEG recordings further support this by showing mixed patterns of alpha waves (indicative of wakefulness) interspersed with REM-like theta and delta activity, reflecting the dissociated state where conscious awareness emerges amid ongoing REM processes.^[20]^[14] Threat hypervigilance during sleep paralysis has been associated with emotional processing involving the amygdaloid complex, which may amplify perceived dangers, particularly in intruder-type hallucinations where individuals sense a menacing presence. Basic brainstem mechanisms, including sublaterodorsal nucleus activity maintaining muscle atonia, underlie the immobility that intensifies this hypervigilance.^[21] Recent research since 2020, utilizing polysomnography, has elucidated how irregular sleep architecture contributes to prolonged sleep paralysis episodes. Studies demonstrate that fragmented REM sleep cycles and reduced REM latency correlate with extended durations of the dissociated state, as evidenced by prolonged atonia alongside preserved rapid eye movements and sawtooth waves. A 2025 review confirms the central role of brainstem neural circuits in REM-wake dissociation underlying sleep paralysis pathogenesis.^[14]^[22] For instance, EEG-polysomnography analyses reveal intermediate spectral power in non-REM bands during episodes, linking overall sleep fragmentation—common in conditions like insomnia—to more severe and lingering intrusions of REM elements into wakefulness.^[14] These findings highlight the role of disrupted sleep continuity in sustaining brain activity imbalances that perpetuate sleep paralysis.

Causes and Risk Factors

Biological Contributors

Sleep paralysis exhibits a moderate genetic component, with twin studies estimating heritability at approximately 53% (95% CI: 0.00–0.70), indicating that genetic factors significantly contribute to its occurrence alongside environmental influences.^[23] This heritability suggests a familial predisposition, though specific genetic variants remain under investigation; for instance, polymorphisms in the PER2 gene, which regulates circadian rhythms, have shown preliminary associations with sleep paralysis in additive and dominant models, albeit not surviving multiple-testing corrections.^[23] In cases linked to narcolepsy, particularly type 1, sleep paralysis is strongly associated with human leukocyte antigen (HLA) genes, notably the DQB1*0602 allele, which is present in over 90% of affected individuals and predisposes to the disorder's full symptom tetrad, including sleep paralysis.^[24] This genetic marker influences immune function and is implicated in the autoimmune destruction of orexin-producing neurons in the hypothalamus, leading to orexin (hypocretin) deficiency that disrupts REM sleep regulation and manifests as isolated or comorbid sleep paralysis episodes.^[25] However, sleep paralysis frequently occurs in isolation without narcolepsy, affecting non-narcoleptic populations and highlighting its broader physiological vulnerability beyond orexin-related pathology.^[23] Hormonal disruptions also play a role in predisposing individuals to sleep paralysis by altering sleep-wake transitions. Irregular melatonin secretion, often due to disrupted circadian entrainment from factors like excessive evening light exposure, can destabilize the timing of REM sleep onset, promoting incomplete transitions to wakefulness where muscle atonia persists.^[26] Similarly, elevated or prolonged cortisol levels, particularly in females via heightened hypothalamic-pituitary-adrenal axis activity, contribute to fragmented sleep architecture and increased vulnerability to these episodes during stress-modulated rhythms.^[26]

Lifestyle and Environmental Triggers

Lifestyle factors, particularly those disrupting normal sleep patterns, significantly contribute to the frequency of sleep paralysis episodes. Irregular sleep schedules, such as going to bed after midnight, have been associated with increased odds of experiencing sleep paralysis, with odds ratios ranging from 1.28 to 1.36.^[27] Sleep deprivation, defined as sleeping less than six hours per night, further elevates this risk, showing an odds ratio of 3.50 (95% CI: 1.80–6.70).^[27] Jet lag, which alters circadian rhythms through rapid time zone changes, is linked to more frequent sleep paralysis occurrences due to the resulting misalignment of sleep-wake cycles.^[28] Shift work, involving non-standard hours that fragment sleep, also heightens vulnerability, with prevalence rates of 48% among shift workers compared to 36% in those with regular schedules.^[27] Environmental conditions, including sleeping posture, play a role in triggering episodes. The supine (back-lying) position during sleep onset or episodes is reported 3 to 4 times more frequently in sleep paralysis cases than in typical sleep, potentially due to increased respiratory or positional discomfort that heightens arousal during REM transitions.^[29] Psychological stressors exacerbate the impact of these sleep disruptions. Anxiety disorders are a significant predictor, with an odds ratio of 1.39 (95% CI: 1.13–1.71) for sleep paralysis occurrence.^[27] Post-traumatic stress disorder (PTSD) shows even stronger associations, with prevalence rates of 65% to 100% among affected individuals compared to 20% to 25% in the general population.^[27] These stressors can amplify biological predispositions, such as genetic vulnerabilities, leading to greater episode frequency.^[30] Substance use interferes with REM sleep regulation, thereby increasing sleep paralysis risk. Daily alcohol consumption is linked to higher odds, ranging from 1.23 to 1.84 across studies.^[27] Nicotine use shows mixed but generally positive associations, with one study reporting an odds ratio of 1.16.^[27] In contrast, caffeine consumption demonstrates no significant link to sleep paralysis.^[27] Recent research on cannabis suggests potential disruptions to REM sleep architecture, which may indirectly heighten vulnerability, though direct associations remain under investigation.^[31]

Diagnosis

Clinical Assessment

The diagnosis of sleep paralysis, specifically recurrent isolated sleep paralysis (RISP), relies on established criteria from the International Classification of Sleep Disorders, Third Edition, Text Revision (ICSD-3-TR). These criteria require recurrent episodes of inability to move the trunk or limbs at sleep onset or upon awakening, accompanied by preserved consciousness; the episodes must occur independently of narcolepsy and not be better explained by another sleep, medical, neurological, or mental disorder; they must cause clinically significant distress or impairment in social, occupational, or other areas of functioning; and the disturbance must not be attributable to the effects of a substance such as a drug of abuse or medication.^[32] Episodes typically last from seconds to a few minutes and involve full awareness, often with associated anxiety, though hallucinations are not required for diagnosis. Clinical evaluation begins with a detailed patient history to confirm the presence and characteristics of episodes. Clinicians assess the frequency, duration, timing (hypnagogic at sleep onset or hypnopompic upon awakening), and potential triggers such as irregular sleep schedules, stress, or supine sleeping position. Patients are queried about associated features like perceived pressure on the chest or fear, while ruling out explanations like narcolepsy through absence of cataplexy or excessive daytime sleepiness. To aid documentation, sleep diaries tracking episode patterns over weeks are recommended, alongside validated questionnaires such as the Waterloo Unusual Sleep Experiences Questionnaire (WUSEQ), which evaluates sleep paralysis frequency and phenomenology, or the Sleep Paralysis Experiences and Phenomenology Questionnaire (SP-EPQ) for detailed symptom profiling.^[33]^[34] If history suggests overlap with other conditions, physical and neurological examinations are performed, including electroencephalography (EEG) to exclude epileptic seizures that may mimic immobility. Overnight polysomnography (PSG) may be indicated in cases of frequent episodes or suspicion of underlying disorders like narcolepsy, recording brain waves, muscle activity, and eye movements to confirm REM-related atonia intrusion into wakefulness without epileptiform activity. Routine laboratory tests or imaging are not typically required unless comorbid medical issues are suspected.^[35]^[36]

Differential Considerations

Sleep paralysis requires careful differentiation from other sleep and neurological disorders to prevent misdiagnosis, as symptoms of immobility and distress can overlap. Key differential considerations include narcolepsy with cataplexy, night terrors, REM sleep behavior disorder (RBD), and nocturnal panic attacks.^[37]^[14] Narcolepsy often presents with sleep paralysis as a core symptom, but is distinguished by the presence of cataplexy—sudden muscle weakness triggered by emotions—and excessive daytime sleepiness, which are absent in isolated sleep paralysis; polysomnography with multiple sleep latency testing can confirm narcolepsy if these features are present.^[37]^[14] Night terrors, occurring during non-REM sleep, involve sudden arousal with screaming, intense fear, and no awareness or detailed recall, in contrast to sleep paralysis, which features preserved consciousness, vivid hypnagogic or hypnopompic hallucinations, and REM-related muscle atonia without vocalization.^[37]^[14] REM sleep behavior disorder differs from sleep paralysis by the absence of atonia, leading to physical enactment of dreams—often violent—during REM sleep, whereas sleep paralysis maintains paralysis with awareness upon waking.^[37]^[14] Nocturnal panic attacks, typically arising from non-REM sleep, manifest as abrupt fear with autonomic arousal like tachycardia but lack the characteristic paralysis and sleep-transition-specific hallucinations seen in sleep paralysis.^[37] Rare overlaps occur with epilepsy, particularly atonic seizures that cause sudden falls or immobility mimicking paralysis, and with hypnagogic hallucinations in schizophrenia, where perceptual disturbances may resemble those in sleep paralysis but persist beyond sleep-wake transitions with impaired reality testing.^[37]^[9] The International Classification of Sleep Disorders, Third Edition, Text Revision (ICSD-3-TR) guidelines emphasize excluding these conditions through clinical history, and for atypical cases suggesting neurological involvement like epilepsy, neuroimaging such as MRI is recommended to identify structural abnormalities.^[38]^[39] Standard clinical assessment tools, including sleep diaries and polysomnography, aid in these distinctions when symptoms are ambiguous.^[37]

Management

Prevention Methods

Improving sleep hygiene represents a primary evidence-based strategy for preventing sleep paralysis episodes, as poor sleep quality is strongly correlated with increased occurrence. Key practices include maintaining a consistent sleep schedule by adhering to the same bedtime and wake-up time daily, even on weekends, to regulate circadian rhythms and minimize disruptions during REM sleep transitions. Additionally, limiting daytime naps to short durations or avoiding them altogether can help consolidate nighttime sleep and reduce the risk of fragmented rest that may trigger episodes. Creating an optimal sleep environment—such as using a comfortable mattress and pillow, dimming lights, and reducing noise—further supports uninterrupted sleep, while avoiding stimulants like caffeine and alcohol in the evening prevents interference with sleep architecture.^[2]^[4] Stress management techniques also play a crucial role in prevention, given the association between heightened anxiety and sleep paralysis. Practices such as mindfulness meditation, deep breathing exercises, or progressive muscle relaxation before bed can mitigate stress-induced disruptions to sleep onset and maintenance. For instance, focused-attention meditation combined with muscle relaxation has demonstrated clinical benefits in reducing episode frequency by stabilizing REM sleep patterns. Incorporating daily stress-reduction activities, like journaling or therapy, fosters overall emotional resilience and supports better sleep continuity.^[2]^[40]^[4] Positional therapy offers another targeted approach, as sleeping on the back has been correlated with a higher incidence of sleep paralysis due to potential airway pressure and altered breathing patterns during sleep transitions. Encouraging side-sleeping positions, possibly aided by pillows to maintain alignment, can help lower this risk without requiring additional interventions. This adjustment is particularly beneficial for individuals who frequently experience episodes in the supine position.^[36]^[11]

Treatment Approaches

Treatment for sleep paralysis primarily involves therapeutic interventions aimed at reducing the frequency and severity of episodes, often following a confirmed diagnosis. Pharmacological options focus on medications that modulate rapid eye movement (REM) sleep, as sleep paralysis is closely linked to REM atonia dysregulation. Low-dose tricyclic antidepressants, such as clomipramine at 25–50 mg daily, have been reported to effectively decrease the occurrence of sleep paralysis episodes by suppressing REM sleep.^[37] Similarly, selective serotonin reuptake inhibitors (SSRIs) and other antidepressants like imipramine (25–150 mg daily) or protriptyline (10–40 mg daily) are commonly prescribed off-label for this purpose, though evidence is primarily from case series and clinician observations rather than large-scale trials.^[41] These treatments carry caveats, including potential side effects such as anticholinergic effects, sedation, dry mouth, and cardiovascular risks associated with tricyclic antidepressants, necessitating careful monitoring and individualized dosing.^[37] Psychological interventions, particularly adaptations of cognitive behavioral therapy (CBT) for insomnia, target the fear and anxiety that exacerbate sleep paralysis episodes. CBT for isolated sleep paralysis incorporates elements like sleep hygiene education tailored to sleep paralysis triggers, relaxation techniques to employ during episodes, and cognitive restructuring to reframe catastrophic interpretations of paralysis and associated hallucinations.^[37] This approach emphasizes reducing anticipatory anxiety, which can perpetuate the cycle of recurrent episodes, and has shown promise in clinical settings for improving episode management and overall sleep quality.^[41] Evidence from randomized controlled trials on related REM parasomnias, such as nightmares in narcolepsy, supports the efficacy of CBT in diminishing sleep paralysis frequency and associated distress, with adaptations demonstrating reduced fear responses in participants.^[42] Emerging treatments explore innovative methods to empower individuals during episodes, including lucid dreaming training to foster awareness and control. Techniques such as reality testing and wake-induced lucid dreaming induction allow individuals to recognize and navigate sleep paralysis states, potentially transforming terrifying experiences into manageable ones, supported by preliminary case reports and neuroimaging evidence linking lucid dreaming to heightened prefrontal cortex activity during REM.^[43]

Epidemiology

Global Prevalence

Sleep paralysis exhibits a wide range of prevalence worldwide, with lifetime estimates in the general population varying from approximately 8% to over 30% based on systematic reviews. A 2024 meta-analysis of 76 studies involving 167,133 participants across 25 countries reported a global lifetime prevalence of 30% (95% CI: 22%-39%), encompassing both isolated and non-isolated episodes. Earlier reviews, such as a 2011 synthesis of 35 studies with 36,533 participants, estimated a lower lifetime rate of 7.6% in the general population, highlighting potential methodological differences in assessment and reporting.^[44]^[45] Prevalence is notably higher among specific groups, such as students, where rates can reach up to 40%. The same 2024 meta-analysis found a lifetime prevalence of 34% (95% CI: 23%-47%) among non-psychiatric students, consistent with patterns of irregular sleep and stress in this demographic. In contrast, psychiatric patients experience rates around 35% (95% CI: 20%-55%), underscoring the role of underlying mental health conditions in elevating risk.^[44] Cross-cultural variations reveal higher reported rates in East Asian populations compared to Western ones. For instance, a 1987 study in Japan documented a lifetime prevalence of approximately 40% for isolated sleep paralysis (known locally as kanashibari), based on surveys of over 700 adults. In Western contexts, such as the United States, college student prevalence is around 24.5%, while general population rates from longitudinal data hover between 9.7% and 15.1% over recent years. These differences may stem from cultural awareness, sleep practices, and study designs, though direct comparisons remain limited.^[46]^[47]^[48] Recent trends indicate rising occurrences, potentially linked to global disruptions like the COVID-19 pandemic, which exacerbated sleep irregularities and stress. A 3-year longitudinal study in the US general population (2013-2016) showed prevalence increasing from 9.7% (95% CI: 9.1%-10.3%) to 15.1% (95% CI: 14.4%-15.8%), with an annual incidence of 2.7% (95% CI: 2.4%-3.0%) for new cases.^[48]

Demographic Patterns

Sleep paralysis exhibits distinct demographic patterns, with prevalence varying significantly across age groups, genders, and populations with specific comorbidities. Research indicates that the condition most commonly begins in adolescence or young adulthood, often with first episodes occurring around ages 14 to 17.^[2] Episodes tend to be more frequent in individuals aged 18 to 30 years, gradually declining thereafter and becoming less common after age 40, possibly due to changes in sleep architecture and reduced REM sleep intensity with advancing age.^[49]^[2] Gender differences show a slightly elevated prevalence among females, with lifetime rates reported at approximately 18.9% for women compared to 15.9% for men, yielding a modest ratio of about 1.2:1.^[45] However, some studies find no significant gender-based risk when controlling for other factors like sleep quality.^[50] Comorbidities play a prominent role in demographic patterns, particularly with mental health conditions. There is a notable overlap of 30-50% between sleep paralysis and anxiety disorders or posttraumatic stress disorder (PTSD), with lifetime prevalence reaching 31.9% among psychiatric patients overall and up to 76% in those with PTSD.^[45]^[18] This association is bidirectional, as sleep paralysis can exacerbate anxiety symptoms, while underlying stress from these disorders may heighten REM sleep intrusions.^[9] Additionally, recent analyses highlight higher rates in Black, Indigenous, and People of Color (BIPOC) populations, with lifetime prevalence of 40.2% in general population samples of African descent compared to 36.9% in Caucasian samples overall, potentially attributable to chronic stress from socioeconomic and racial inequities.^[45]^[10]

Cultural and Historical Context

Etymology and Terminology

The term "sleep paralysis" was first introduced in medical literature in 1928 by British neurologist Samuel Alexander Kinnier Wilson in his work on narcolepsy, where he described episodes of temporary immobility during the transition between sleep and wakefulness.^[13] The word "paralysis" itself derives from the ancient Greek "parálusis," meaning a loosening or disabling, combining "para-" (beside or alongside) and "lúein" (to loosen), reflecting the sudden loss of voluntary muscle control.^[51] Earlier descriptions of the phenomenon appeared under other names, such as "night palsy" coined by Silas Weir Mitchell in 1876, but Wilson's terminology established the modern clinical label.^[13] Various alternative terms for sleep paralysis have emerged from cultural and regional contexts, often tied to folklore interpretations of the experience. In Newfoundland, Canada, it is commonly known as "Old Hag syndrome," referring to a belief in a spectral hag or witch that sits on the chest of the sleeper, causing oppression and immobility—a term documented in local ethnographic studies since the mid-20th century.^[6] In Japan, the condition is called "kanashibari," which translates to "bound by metal" or "metal-binding," originating from Buddhist traditions where it was attributed to spiritual binding by vengeful entities or supernatural forces. In contemporary medical classification, sleep paralysis has been standardized as "isolated sleep paralysis" when occurring independently of other disorders, first codified as a distinct entity in the International Classification of Sleep Disorders, Revised (ICSD-R) in 1997 and further refined in the ICSD-3 edition released in 2014, categorizing it as a REM sleep parasomnia. The DSM-5, published in 2013, does not list it as a standalone disorder but recognizes recurrent episodes under "other specified sleep-wake disorder" or as a symptom of narcolepsy, emphasizing its clinical significance when distressing.^[9] These classifications highlight a shift from folkloric explanations to a unified scientific framework, though cultural terms persist in popular discourse.^[37]

Folklore Across Cultures

Sleep paralysis has been interpreted across cultures as an assault by supernatural entities, often involving a sense of pressure on the chest, immobility, and terrifying hallucinations of demons, witches, or spirits.^[52] This motif recurs globally, where the experience is attributed to malevolent beings that visit during vulnerable moments of sleep, reflecting shared human fears of the unseen.^[6] In Albania, the phenomenon is linked to Mokthi, a male spirit wearing a golden fez hat who targets tired or sorrowful women, sitting on their chest to induce paralysis and nightmares.^[53] Cambodian folklore describes Khmaoch Sângkât, or "the ghost that pushes you down," an ancestral or vengeful spirit—often visualized as a Khmer Rouge soldier with canine teeth—that presses on the sleeper, particularly among refugees where it exacerbates trauma-related episodes.^[54] In Egypt, sleep paralysis is frequently ascribed to jinn, invisible malevolent spirits from Islamic tradition that terrorize and sometimes strangle victims, with nearly half of the general population endorsing this belief in a 2013 cross-cultural study.^[55] Japanese culture refers to it as kanashibari, or "metal-binding," caused by vengeful ghosts or spirits summoned to suffocate enemies, a concept depicted in traditional tales and modern media.^[52] Among the Yoruba in Nigeria, Ogun Oru (nocturnal warfare) involves a female demon that possesses individuals during sleep, leading to paralysis interpreted as spiritual attack or witchcraft.^[52] These beliefs persist into the 2020s, as seen in anthropological surveys of Turkish Karabasan—a demon-like entity causing heaviness and fear—and Italian Pandafeche, a witch that binds sleepers, with attribution to supernatural causes reported by 17% in a Turkish study and over one-third in an Italian study, despite scientific awareness.^[56]^[57] Psychological research indicates a priming effect, where cultural exposure to these folklore narratives heightens the intensity of fear, hallucination vividness, and episode reporting; for instance, Egyptian participants in intercultural comparisons experienced greater terror and longer durations when primed by jinn beliefs compared to those in Denmark.^[55] Similarly, among Cambodian refugees, cultural interpretations of Khmaoch Sângkât amplified distress in PTSD-linked cases, increasing recurrence rates up to 42% in early 2000s studies that inform ongoing 2020s anthropological work.^[52] This cultural shaping underscores how shared myths transform a universal physiological event into regionally specific supernatural ordeals.^[6]

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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 ...
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Research in human narcolepsy has led to the identification of specific HLA alleles (DQB1*0602 and DQA1*0102) that predispose to the disorder.
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Apr 18, 2011 · Narcolepsy is a chronic neurodegenerative disease caused by a deficiency of orexin-producing neurons in the lateral hypothalamus.Narcolepsy And Orexins: The... · Orexins And Human Narcolepsy · Loss Of Orexin Neurons: The...
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Jet lag syndrome: circadian organization, pathophysiology, and ...
Aug 19, 2010 · For instance, jet lag has been associated with more frequent sleep paralysis (lack of muscle control after arousal from sleep) episodes.68 The ...
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Situational factors affecting sleep paralysis and associated ...
The supine position was also 3-4 times more common during SP than when normally falling asleep. The supine position during SP was reported to be more prevalent ...Missing: scholarly | Show results with:scholarly
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Relationships between sleep paralysis and sleep quality - NIH
Nov 2, 2018 · Sleep paralysis is the unusual experience of waking up in the night without the ability to move. Currently little is known about the experience, ...Objective Sleep Measurements · Sleep Paralysis In Other... · Insomnia Disorder
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Cannabis and sleep disorders: not ready for prime time? A ...
The utilization of cannabis showed improved sleep (21%), worse sleep (48%), mixed results (14%), or no impact at all (17%) in the studies published in the last ...
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[PDF] Parasomnias - American Academy of Sleep Medicine
Recurrent isolated sleep paralysis is characterized by an inability to initiate voluntary movements at sleep onset (hypnagogic or predormital form) or on ...<|control11|><|separator|>
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the Unusual Sleep Experiences Questionnaire (USEQ) - PubMed
Previous research has found a relationship between sleep paralysis (SP) and anxiety states and higher rates have been reported among certain ethnic groups.
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Characteristics of Sleep Paralysis and Its Association with Anxiety ...
SP episodes are often accompanied by various psychosomatic sensations, among which are the occurrence of the feeling of pressure on the chest, difficulty ...Missing: immobility autonomic
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Focal epileptic seizures mimicking sleep paralysis - ScienceDirect.com
As possible differential diagnoses of sleep paralyses include focal epileptic seizures, assessment including both VPSG and prolonged video-EEG-monitoring ...
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Sleep paralysis: Causes, symptoms, and treatments - Harvard Health
Oct 20, 2023 · Because it is linked to the rapid eye movement (REM) stage of the sleep cycle, sleep paralysis is considered a REM parasomnia. You may be ...
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A clinician's guide to recurrent isolated sleep paralysis - PMC - NIH
Jul 19, 2016 · As per the current ICSD-31 criteria, RISP consists of multiple episodes of isolated SP that are associated with clinically significant distress ...
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Aug 13, 2024 · A summary of diagnostic criteria revisions made in ICSD-3-TR, as well as the literature search terms and resulting references used as supporting ...
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Neuroimaging Findings in Sleep Disorders: A Review Article
### Summary of Sleep Paralysis-Related Content from Neuroimaging Findings in Sleep Disorders Review
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A clinician's guide to recurrent isolated sleep paralysis | NDT
Jul 19, 2016 · This review summarizes the empirical and clinical literature on sleep paralysis most relevant to practitioners.Missing: neuroimaging atypical
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Treating narcolepsy‐related nightmares with cognitive behavioural ...
Oct 22, 2024 · ... sleep paralysis, sleep-related hallucinations, dream delusions ... Cognitive Behavioral Therapy for Nightmares: Therapist guide. http ...
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The clinical neuroscience of lucid dreaming - ScienceDirect.com
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Functional changes in sleep-related arousal after ketamine ... - Nature
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Global Incidence and Clinical Characteristics of Sleeping Paralysis
Apr 9, 2024 · Objective:Our objectives are to identify SP's global prevalence, the affected population's characteristics, and the SP's clinical picture.
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Lifetime Prevalence Rates of Sleep Paralysis: A Systematic Review
7.6% of the general population, 28.3% of students, and 31.9% of psychiatric patients experienced at least one episode of sleep paralysis.
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High prevalence of isolated sleep paralysis: kanashibari ... - PubMed
Of all subjects, about 40% had experienced at least one episode of kanashibari [subjects of K(+)]. Therefore, isolated sleep paralysis is apparently a more ...Missing: East Asia
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Comparative Prevalence of Isolated Sleep Paralysis in Kuwaiti ...
Aug 6, 2025 · Using the item "unable to move," 28.8% of Kuwaiti, 29.9% of Sudanese, and 24.5% of American participants reported experiencing the disorder at ...<|control11|><|separator|>
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Prevalence, incidence, evolution and associated factors of sleep ...
Jun 11, 2022 · 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 ...Missing: annual | Show results with:annual
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Oct 4, 2022 · In several systematic reviews and meta-analyses, sleep disturbance in post-COVID-19 patients ranged between 27.4 and 47% [32–39].
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Sleep Paralysis Statistics Statistics: ZipDo Education Reports 2025
May 30, 2025 · The prevalence of sleep paralysis among psychiatric patients can be as high as 40%; Sleep paralysis is reported more frequently in females ...
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Gender medicine and sleep disorders: from basic science to clinical ...
Jul 9, 2024 · According to some gender studies, the incidence has been found to vary, from slightly higher in males (76–79) to higher in females (80, 81).
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Risk factors of sleep paralysis in a population of Polish students
Jun 7, 2022 · Mental and somatic health problems and lifestyle factors were found to predispose individuals to this disorder. Due to the numerous risk factors ...
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Paralysis - Etymology, Origin & Meaning
Paralysis, from Greek "paralysis" meaning "loosening," combines para- (beside) + lyein (loosen). It means nervous impairment causing loss of movement or ...
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Sleep Paralysis in Brazilian Folklore and Other Cultures - NIH
Sep 7, 2016 · In the Japanese tradition, SP is due to a vengeful spirit who suffocates his enemies while sleeping. In Nigerian culture, a female demon attacks ...
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Sleep paralysis & The intersection of brain, trauma, traditions
The precise causes of sleep paralysis remain unclear, but research suggests a strong link with disruptions in the REM sleep cycle. During REM sleep, muscle ...Sleep Paralysis: A Deep Dive · Sleep Paralysis: The Pain... · Sleep Paralysis: Study...<|control11|><|separator|>
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When Ghosts Try to Kill You In Your Sleep - VICE
Jun 6, 2017 · In Cambodia, it's khmaoch sângkât. In every country, there's a ... sleep paralysis”: it's the work of some kind of spirit, or, to ...
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Explanations of sleep paralysis among Egyptian college students ...
Oct 1, 2013 · This cross-cultural study compared explanations of sleep paralysis (SP) in two countries and two groups with different levels of education in one country.
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Beliefs about sleep paralysis in Turkey: Karabasan attack - PMC - NIH
Karabasan refers to a creature in Turkish folklore that is believed to cause paralysis upon falling asleep or awakening, or it can simply refer to the ...<|control11|><|separator|>
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Sleep paralysis in Italy: Frequency, hallucinatory experiences, and ...
Previous research has found supernatural beliefs about sleep paralysis (SP) to be very prevalent in Italy, with over one third of SP sufferers believing ...