A Cannabis Harm Reduction e-Intervention for Young Cannabis Users With Early Psychosis

This multicentric, two-arm, open-labelled, pilot randomized controlled trial involves 100 young cannabis users who experienced a psychosis and are followed in an early intervention service (EIS) in Canada. Participants will be randomized in a 1:1 ratio to one of two interventions: * CHAMPS and EIS * EIS alone The smartphone application CHAMPS contains six modules (each lasting 15-20 min, weeks 1 to 6) and a booster session (20 min, week 10) based on motivational interviewing and harm reduction approaches. EIS consists of standard of care and psychoeducation material on cannabis use offered in first episode psychosis clinics and administered through in-person visits and/or phone or video calls. All participants will be assessed for a follow-up at weeks 6, 12 and 18. Data on mental health, substance use, cannabis dependence severity, cannabis-related problems, quality of life and health care service utilization will be obtained through questionnaires and medical charts.