Short term impact of same intensity but different duration interventions for cannabis users.

The present study evaluates the efficacy of a brief intervention for cannabis users. A randomized controlled trial compared 3 conditions: 4 weekly individual sessions of motivational interviewing and relapse prevention over 1 month (1MIRP); the same 4 sessions over 3 months (3MIRP), and delayed treatment control (DTC). The short term impact of each intervention was followed up 4 months after randomization. Participants were 160 highly educated adults with a long history of frequent cannabis use. Both treatments showed better results than the DTC, and for primary outcomes (i.e., cannabis consumption) there was no difference between treatments, while the 3MIRP scheme showed greater efficacy in reducing dependence symptoms and other drug use according to the ASI drug subscale. There was a tendency for the longer treatment to have better outcomes, regardless of intensity, although the waiting list did have some positive effect. The cohort needs to be followed up for a longer period in order to ascertain whether changes are maintained over time.