• Cannabis use is associated with increased psychotic symptoms and poorer psycho-social functioning in first-episode psychosis: A report from the UK National EDEN study

      Seddon, Jennifer L.; Birchwood, Max; Copello, Alex; Everard, Linda; Jones, Peter B.; Fowler, David; Amos, Tim; Freemantle, Nick; Sharma, Vimal; Marshall, Max; et al. (Oxford University Press, 2015-11-04)
      Background: 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 psychosis (FEP) and the link with symptomatic course and outcome over one year post psychosis onset. Method: 1027 FEP patients were recruited upon inception to specialised early intervention services for psychosis in the UK. Participants completed assessments at baseline, six and twelve months. Results: The results indicate that the use of cannabis was significantly associated with increased severity of psychotic symptoms, mania, depression and poorer psycho-social functioning. Continued use of cannabis following the first episode of psychosis was prognostic of outcome at one year. These associations were significant after adjusting for age, gender, DUP, age of psychosis onset, ethnicity and other drug use. Conclusion: This is the largest cohort study of first-episode psychosis patients receiving care within early intervention services. Cannabis use, in particular continued use, is associated with poorer symptomatic and functional outcome during the first-episode of psychosis. The results highlight the need for effective and early intervention for cannabis use in FEP.