Clinical features of isolated sleep paralysis.

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.

Study at a glance

Abstract

OBJECTIVE Isolated sleep paralysis (ISP) is a relatively common parasomnia often accompanied by fear and distress. However, little is known about the range and relative severities of typical ISP symptoms and accompanying hallucinations. Furthermore, there have been inconsistent findings with regard to demographic differences in ISP. PATIENTS/METHOD In sum, 185 individuals with ISP (and 322 controls) were assessed for 27 symptoms and hallucinations using a clinical interview and trained diagnosticians. Insomnia symptoms were also assessed. RESULTS Rates of ISP did not differ according to gender or ethnic minority status, but higher levels of insomnia were associated with episodes. The participants with ISP reported a mean of 7.73 symptoms beyond atonia. Hallucinations of the presence of others were relatively common. Specifically, 57.84% of the sample sensed a presence in the room with them during ISP, and the majority believed it to be a non-human presence. In addition, 21.62% of the sample experienced visual hallucinations of others, with the majority perceiving strangers as opposed to known individuals. A panoply of supernatural/paranormal entities were reported by the 24.32% of participants who hallucinated non-human beings. A minority of individuals with ISP experienced clinically-significant distress (10.27%) and/or impairment (7.57%) as a result of episodes. CONCLUSION ISP episodes were complex and often multisensorial experiences, and the majority of assessed symptoms were associated with clinically-significant levels of fear/distress. Vivid hallucinations of other people and entities were common as well, and it is recommended that ISP be assessed when patients report seemingly anomalous experiences.