title: Cannabis Use Is Associated With Increased Psychotic Symptoms and Poorer Psychosocial Functioning in First-Episode Psychosis: A Report From the UK National EDEN Study.
abstract: OBJECTIVE
  The use of cannabis during the early stage of psychosis has been linked with increased psychotic symptoms. This study aimed to examine the use of cannabis in the 12 months following a first-episode of psychosis (FEP) and the link with symptomatic course and outcome over 1 year post psychosis onset.
  
  
  METHODS
  One thousand twenty-seven FEP patients were recruited upon inception to specialized early intervention services (EIS) for psychosis in the United Kingdom. Participants completed assessments at baseline, 6 and 12 months.
  
  
  RESULTS
  The results indicate that the use of cannabis was significantly associated with increased severity of psychotic symptoms, mania, depression and poorer psychosocial functioning. Continued use of cannabis following the FEP was associated with poorer outcome at 1 year for Positive and Negative Syndrome Scale total score, negative psychotic symptoms, depression and psychosocial functioning, an effect not explained by age, gender, duration of untreated psychosis, age of psychosis onset, ethnicity or other substance use.
  
  
  CONCLUSIONS
  This is the largest cohort study of FEP patients receiving care within EIS. Cannabis use, particularly "continued use," was associated with poorer symptomatic and functional outcome during the FEP. The results highlight the need for effective and early intervention for cannabis use in FEP.
authors.affiliation: National Drug & Alcohol Research Centre, UNSW, Sydney, Australia; jennifer.l.seddon@gmail.com.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Seddon
authors.affiliation: Mental Health and Wellbeing Warwick Medical School, University of Warwick, Coventry, UK;
authors.forename: Max
authors.initials: M
authors.lastname: Birchwood
authors.affiliation: School of Psychology, University of Birmingham, Birmingham, UK; The Early Intervention Service, Birmingham and Solihull Mental Health NHS Foundation Trust, Birmingham, UK;
authors.forename: Alex
authors.initials: A
authors.lastname: Copello
authors.affiliation: The Early Intervention Service, Birmingham and Solihull Mental Health NHS Foundation Trust, Birmingham, UK;
authors.forename: Linda
authors.initials: L
authors.lastname: Everard
authors.affiliation: Department of Psychiatry, University of Cambridge and CAMEO, Cambridge and Peterborough NHS Foundation Trust, Cambridge, UK;
authors.forename: Peter B
authors.initials: PB
authors.lastname: Jones
authors.affiliation: Department of Psychology, University of Sussex, Brighton, UK;
authors.forename: David
authors.initials: D
authors.lastname: Fowler
authors.affiliation: Academic Unit of Psychiatry, University of Bristol, Bristol, UK;
authors.forename: Tim
authors.initials: T
authors.lastname: Amos
authors.affiliation: Department of Primary Care and Population Health, UCL Medical School (Royal Free Campus), London, UK;
authors.forename: Nick
authors.initials: N
authors.lastname: Freemantle
authors.affiliation: Early Intervention Service, Cheshire and Wirral NHS Foundation Trust, Chester, UK; Faculty of Health and Social Care, University of Chester, Chester, UK;
authors.forename: Vimal
authors.initials: V
authors.lastname: Sharma
authors.affiliation: School of Medicine, University of Manchester, Manchester, UK.
authors.forename: Max
authors.initials: M
authors.lastname: Marshall
authors.affiliation: Mental Health and Wellbeing Warwick Medical School, University of Warwick, Coventry, UK;
authors.forename: Swaran P
authors.initials: SP
authors.lastname: Singh
mesh_terms: D000293:Adolescent; D000328:Adult; D002188:Cannabis / Q000009:adverse effects*; D061345:Early Medical Intervention / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D017063:Outcome Assessment, Health Care; D011605:Psychoses, Substance-Induced / Q000503:physiopathology / Q000628:therapy; D011618:Psychotic Disorders / Q000503:physiopathology* / Q000628:therapy; D006113:United Kingdom; D055815:Young Adult
keywords: cannabis use; first-episode psychosis; prospective study; psychotic symptoms