Continued cannabis use and outcome in first-episode psychosis: data from a randomized, open-label, controlled trial

Cannabis use has been found to increase the risk of psychosis. It is unclear whether, after a first psychotic episode has occurred, continued cannabis use is associated with poor functional outcome of psychosis.

As part of a randomized, open-label, controlled trial, the association of cannabis use and measures for psychopathology and social role functioning after 2 years of follow-up and for the recently proposed outcome measures of symptomatic remission, functional remission, and clinical recovery was explored in a group of 124 patients suffering from nonaffective first-episode psychosis (diagnosed according to DSM-IV and included from a catchment area in the Netherlands of 3.1 million inhabitants from October 2001 through December 2002). Other patient characteristics that were expected to be independently associated with outcome, among them alcohol and other drug use, were assessed at baseline.

Continued cannabis use was not associated with symptomatic or functional remission or clinical recovery. After 2 years, cannabis use was related to certain aspects of social role functioning (economic and social activities; explained variance 5.6% and 8.4%, respectively) but not to psychopathology (Positive and Negative Syndrome Scale Positive, Negative, or General symptoms).

Our findings support the notion that continued cannabis use after the onset of a first-episode psychosis is correlated with worse social outcome and should be discouraged whenever possible, but its role in outcome is modest in comparison to other factors.

Nederlands Trial Register: http://www.trialregister.nl (ID: NTR 374).