title: Cannabis use in patients with a first psychotic episode and subjects at ultra high risk of psychosis: impact on psychotic- and pre-psychotic symptoms.
abstract: OBJECTIVE
  Co-morbidity with cannabis use disorder is common in patients with a psychotic disorder and is associated with adverse outcome. This study aimed to determine prevalence of cannabis use disorder among patients with a psychotic disorder and subjects at ultra high risk of psychosis and to study the influence of cannabis use on severity of (pre-)psychotic symptomatology, psychosocial functioning and variables related to the course of the disorder in these patients.
  
  
  METHODS
  In this study 169 consecutively assessed patients with a psychotic disorder were included as well as 59 consecutively assessed subjects at ultra high risk of psychosis.
  
  
  RESULTS
  45% of the patients with a psychotic disorder and 27% of the UHR patients were diagnosed with a co-morbid cannabis use disorder. Patients with cannabis use disorders did not differ from patients without cannabis use disorder in severity of psychotic symptoms. However, excluding patients with substance use disorder other than cannabis use disorder resulted in higher scores on positive symptom levels for patients with cannabis use disorder compared to patients without any substance use disorder. Regarding ultra high risk patients, subjects with cannabis use disorder did not differ from subjects without cannabis use disorder on severity of pre-psychotic symptomatology. However, a negative correlation was found between the amount of cannabis used recently and scores on the pre-psychotic negative subscale.
  
  
  CONCLUSIONS
  Our results suggest a specific association between cannabis abuse and psychotic symptomatology.
authors.affiliation: Academic Psychiatric Centre, Department of Early Psychosis, AZ Amsterdam, The Netherlands. m.w.machielsen@amc.uva.nl
authors.forename: Marise
authors.initials: M
authors.lastname: Machielsen
authors.forename: Suzanne
authors.initials: S
authors.lastname: van der Sluis
authors.forename: Lieuwe
authors.initials: L
authors.lastname: de Haan
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D015897:Comorbidity; D017831:Diagnosis, Dual (Psychiatry); D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis* / Q000453:epidemiology*; D015995:Prevalence; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D012720:Severity of Illness Index