Cannabis-related problems
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Total score on the Marijuana Problems Scale
Cannabis use
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Past two weeks cannabis use according to the Timeline Follow-Back Questionnaire
Other drug use
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Past two weeks other drug use according to the Timeline Follow-Back Questionnaire
Psychotic symptoms
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Total score on the Positive and Negative Syndrome Scale
Severity of cannabis dependence
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Total score on the Severity of Dependence Scale
Social support
Time frame: Weeks -2-0 (baseline)
Total score on the Social Provisions Scale
Health service utilization
Time frame: Weeks -2-0 (baseline), 6, 12 and 18
Past month number of emergency visits and days of hospitalization confirmed by medical record abstraction
Safety (adverse events)
Time frame: Weeks 6, 12 and 18
Adverse events and severe adverse events related or not to the study intervention