Stopping cannabis use benefits outcome in psychosis: findings from 10-year follow-up study in the PAFIP-cohort

Objective To examine the long-term (up to 10 years) patterns related to cannabis use in a sample of patients with first episode of psychosis (FEP) and the effect that consumption might have on clinical, functioning, and neurocognition at long-term. Methods Cannabis use was described in 209 FEP patients. Patients were divided into three groups according to cannabis use: persistent users, ex-users, and never-users. Groups were longitudinally (baseline and 10-year follow-up) compared on clinical, functional, and cognitive variables. Results Clinical differences at 10-year follow-up were observed between persistent cannabis users and the other two groups (ex-users and never-users), showing persistent users more severe symptoms (BPRS: x(2) = 15.583, P <= 0.001; SAPS: x(2) = 12.386, P = 0.002) and poorer functionality (DAS: x(2) = 6.067, P = 0.048; GAF: x(2) = 6.635, P = 0.033). Patients who stopped cannabis use prior to the reassessment showed a similar pattern to those who had never consumed. Conclusion The use of cannabis could negatively affect the evolution of the psychotic disorder. Perhaps the negative effects caused by cannabis use could be reversed with the cessation of consumption. It is necessary to make an effort in the intervention toward an early withdrawal from the use of cannabis, since this could play an important role in the prognosis of the disease.