title: Psychotic symptoms in narcolepsy: phenomenology and a comparison with schizophrenia.
abstract: OBJECTIVE
  Patients with narcolepsy often experience pervasive hypnagogic hallucinations, sometimes even leading to confusion with schizophrenia. We aimed to provide a detailed qualitative description of hypnagogic hallucinations and other "psychotic" symptoms in patients with narcolepsy and contrast these with schizophrenia patients and healthy controls. We also compared the prevalence of formal psychotic disorders between narcolepsy patients and controls.
  
  
  METHODS
  We used SCAN 2.1 interviews to compare psychotic symptoms between 60 patients with narcolepsy, 102 with schizophrenia and 120 matched population controls. In addition, qualitative data was collected to enable a detailed description of hypnagogic hallucinations in narcolepsy.
  
  
  RESULTS
  There were clear differences in the pattern of hallucinatory experiences in narcolepsy vs. schizophrenia patients. Narcoleptics reported multisensory "holistic" hallucinations rather than the predominantly verbal-auditory sensory mode of schizophrenia patients. Psychotic symptoms such as delusions were not more frequent in narcolepsy compared to population controls. In addition, the prevalence of formal psychotic disorders was not increased in patients with narcolepsy. Almost half of narcoleptics reported moderate interference with functioning due to hypnagogic hallucinations, mostly due to related anxiety.
  
  
  CONCLUSIONS
  Hypnagogic hallucinations in narcolepsy can be differentiated on a phenomenological basis from hallucinations in schizophrenia which is useful in differential diagnostic dilemmas.
authors.affiliation: Department of Psychiatry, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands. h.droogleever-fortuyn@psy.umcn.nl
authors.forename: Hal A Droogleever
authors.initials: HA
authors.lastname: Fortuyn
authors.forename: G A
authors.initials: GA
authors.lastname: Lappenschaar
authors.forename: Fokko J
authors.initials: FJ
authors.lastname: Nienhuis
authors.forename: Joop W
authors.initials: JW
authors.lastname: Furer
authors.forename: Paul P
authors.initials: PP
authors.lastname: Hodiamont
authors.forename: Cees A
authors.initials: CA
authors.lastname: Rijnders
authors.forename: Gert Jan
authors.initials: GJ
authors.lastname: Lammers
authors.forename: Willy O
authors.initials: WO
authors.lastname: Renier
authors.forename: Jan K
authors.initials: JK
authors.lastname: Buitelaar
authors.forename: Sebastiaan
authors.initials: S
authors.lastname: Overeem
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003702:Delusions / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006212:Hallucinations / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D008297:Male; D009290:Narcolepsy / Q000453:epidemiology*; D015995:Prevalence; D011618:Psychotic Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D012559:Schizophrenia / Q000175:diagnosis* / Q000453:epidemiology*