Isolated sleep paralysis (ISP) is a common parasomnia often accompanied by fear and distress. In 185 individuals with ISP and 322 controls, rates of ISP did not differ by gender or ethnicity, but higher insomnia levels were associated with episodes. Participants reported an average of 7.73 symptoms beyond atonia. Hallucinations of a presence in the room occurred in 57.84% of the sample, most often perceived as non-human. Visual hallucinations of others occurred in 21.62%, mostly strangers. Non-human beings were hallucinated by 24.32%, including various supernatural entities. Clinically significant distress affected 10.27% and impairment 7.57%. ISP episodes are complex and multisensorial, and assessment is recommended when patients report anomalous experiences.
Sleep paralysis is a frightening event in which a person awakens conscious but temporarily unable to move, due to lingering REM-sleep muscle atonia, often accompanied by vivid hallucinations. When it occurs without narcolepsy or other medical conditions, it is called isolated sleep paralysis. The condition is underrecognized by nonsleep specialists, partly because patients are reluctant to disclose episodes and because medical training lacks coverage. A growing body of research documents its prevalence, risk factors, and clinical impact. Available treatments include pharmacological and psychotherapeutic interventions, but these require more empirical support from larger, well-controlled trials.
Lifetime prevalence of sleep paralysis varies by population: 7.6% in the general population, 28.3% in students, and 31.9% in psychiatric patients. Among psychiatric patients with panic disorder, 34.6% reported at least one episode. Minorities experience sleep paralysis at higher rates than Caucasians. The authors conclude that sleep paralysis is relatively common and should be assessed more regularly to understand its impact on functioning and its relation to psychiatric and medical conditions.