title: Cannabis and cognitive performance in psychosis: a cross-sectional study in patients with non-affective psychotic illness and their unaffected siblings.
abstract: BACKGROUND
  The relationship between cannabis use and cognitive functioning in patients with psychosis has yielded contradictory findings. In individuals at genetic high risk for psychosis, information is sparse. The aim of this study was to assess the association between recency and frequency of cannabis use and cognitive functioning in patients with psychosis and their unaffected siblings.
  
  
  METHODS
  We conducted a cross-sectional study in 956 patients with non-affective psychosis, 953 unaffected siblings, and 554 control subjects. Participants completed a cognitive test battery including assessments of verbal learning, set shifting, sustained attention, processing speed, working memory, acquired knowledge, reasoning and problem solving and social cognition. Cannabis use was assessed by urinalysis and by the Composite International Diagnostic Interview. Using random-effect regression models the main effects of cannabis (recency and frequency) and the interaction with status (patient, sibling, control) on cognitive functioning were assessed.
  
  
  RESULTS
  Current cannabis use was associated with poorer performance on immediate verbal learning, processing speed and working memory (Cohen's d -0.20 to -0.33, p<0.005). Lifetime cannabis use was associated with better performance on acquired knowledge, facial affect recognition and face identity recognition (Cohen's d+0.17 to +0.33, p<0.005). There was no significant interaction between cannabis and status on cognitive functioning.
  
  
  CONCLUSIONS
  Lifetime cannabis-using individuals might constitute a subgroup with a higher cognitive potential. The residual effects of cannabis may impair short-term memory and processing speed.
authors: Department of Psychiatry, Academic Medical Center, Amsterdam, The Netherlands.
authors: J H
authors: JH
authors: Meijer
authors: N
authors: N
authors: Dekker
authors: M W
authors: MW
authors: Koeter
authors: P J
authors: PJ
authors: Quee
authors: N J M
authors: NJ
authors: van Beveren
authors: C J
authors: CJ
authors: Meijer
mesh_terms: D000293:Adolescent; D000328:Adult; D003071:Cognition / Q000187:drug effects / Q000502:physiology; D003072:Cognition Disorders / Q000453:epidemiology* / Q000235:genetics / Q000523:psychology; D003430:Cross-Sectional Studies; D013759:Dronabinol / Q000009:adverse effects*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology* / Q000235:genetics / Q000523:psychology; D008875:Middle Aged; D009483:Neuropsychological Tests; D011618:Psychotic Disorders / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D012044:Regression Analysis; D012559:Schizophrenia / Q000453:epidemiology* / Q000235:genetics; D012565:Schizophrenic Psychology; D035781:Siblings / Q000523:psychology*; D055815:Young Adult
chemical_list: D013759:Dronabinol