Relations among hypnagogic and hypnopompic experiences associated with sleep paralysis

The Waterloo Sleep Experiences Scale was developed to assess the prevalence of sleep paralysis and a variety of associated hypnagogic and hypnopompic hallucinoid experiences: sensed presence, felt pressure, floating sensation s, auditory and visual hallucinations, and fear. Consistent with results of recent surveys, almost 30% of 870 university students reported at least on e experience of sleep paralysis. Approximately three-quarters of those also reported at least one hallucinoid experience, and slightly more than 10% e xperienced three or more. Fear was positively associated with hallucinoid e xperiences, most clearly with sensed presence. Regression analyses lend sup port to the hypothesis that sensed presence and fear are primitive associat es of sleep paralysis and contribute to the elaboration of further hallucin oid experiences, especially those involving visual experiences.