Reviewers found inconsistent and, at best, small benefit of MI for substance use; however, it should be noted that studies varied markedly in type of MI interventions, type of substance use, follow‐up durations, outcome measurement, and participant recruitment sites.

MI may yield a small benefit in reducing the extent of substance use compared with no intervention or treatment as usual at intermediate follow‐up (6 to 9 months; low‐certainty evidence), but these effects may not persist longer term (12 to 15 months). MI probably slightly reduces substance use at medium‐term (6 months) and long‐term (12 to 15 months) follow‐up compared with assessment and feedback (moderate‐certainty evidence). However, the available data suggest that MI may have little to no effect on readiness to change or retention in treatment, and no trials assessed cessation of substance use.

When comparing MI with other active interventions (which varied considerably across trials), there may be little to no difference in outcomes.