Study objectives: We investigated a generally unappreciated feature of the sleep disorder narcolepsy, in which patients mistake the memory of a dream for a real experience and form sustained delusions about significant events.
Design: We interviewed patients with narcolepsy and healthy controls to establish the prevalence of this complaint and identify its predictors.
Setting: Academic medical centers in Boston, Massachusetts and Leiden, The Netherlands.
Participants: Patients (n = 46) with a diagnosis of narcolepsy with cataplexy, and age-matched healthy healthy controls (n = 41).
Interventions: N/A.
Measurements and results: "Dream delusions" were surprisingly common in narcolepsy and were often striking in their severity. As opposed to fleeting hypnagogic and hypnopompic hallucinations of the sleep/wake transition, dream delusions were false memories induced by the experience of a vivid dream, which led to false beliefs that could persist for days or weeks.
Conclusions: The delusional confusion of dreamed events with reality is a prominent feature of narcolepsy, and suggests the possibility of source memory deficits in this disorder that have not yet been fully characterized.
Keywords: Dreaming; memory; narcolepsy.