Background: 35%-45% young psychotic patients regularly use cannabis, which may have a negative impact on symptoms, social functioning and relapse. Harm reduction interventions must address specific problems of this population: thought disorders, cognitive impairment, lack of insight, frequent opposition to treatment and various motivations to use cannabis. Our aims were to explore the feasibility of a dual diagnosis brief motivational intervention and its effect on cannabis use and readiness to change in a population of psychotic patients.
Methods: Patients with a psychotic disorder (ICD-10, F2) and cannabis abuse or dependence were included. Intervention consisted of three one-hour sessions: 1) baseline assessment of substance use; 2) motivational interviewing; 3) feedback and definition of objectives according to the stage of change. Substance use was reassessed three months later.
Results: The entire procedure was completed by 85% (11/13) outpatients, but only 20% inpatients. Most patients were at a precontemplation stage of change. Decrease of cannabis use was significant after 3 months (Wilcoxon signed rank test; M1=84 joints, M2=64; Z=_2.2, pb0.05). No significant modifications of the stage of change were found.
Conclusions: Dual diagnosis motivational interviewing (MI) is feasible among ambulatory psychotic patients with cannabis abuse. MI style allowed patients to discuss cannabis use with minimal reactance and enhanced awareness about positive and negative aspects of cannabis use. Cannabis use decreased after three months, but further studies are necessary to prove efficacy of such an intervention.