Isolated sleep paralysis and hypnic hallucinations in schizophrenia

Background: Usually remembered in the context of Narcolepsy-Cataplexy syndrome, isolated sleep paralysis (SP) and hypnic hallucination are widely prevalent and because of the overlap of symptoms with schizophrenia, their identification is important but unrecognized.

Aims: To determine the presence of SP and hypnic hallucinations (HH) in people with schizophrenia and schizoaffective disorder Study

Design: Cross-sectional survey.

Methods: Participants were patients receiving follow-up care for schizophrenia from Assertive Community Treatment Team. A screening questionnaire was administered during their routine follow-up visits.

Results: Of 71 respondents (49 males, 22 females) only 11 (10 males and 1 female), that is, 15% reported SP, and 12 (7 males and 5 females), that is, 16.9% reported HH, a considerably low prevalence.

Conclusion: It is difficult to study the presence of SP and HH in patients with active or residual symptoms of schizophrenia, and more refined studies and appropriate questionnaires are required. The possibility of SP and HH confounding or being misdiagnosed as psychotic symptoms needs to be borne in mind.