Promoting self-change in cannabis use disorder: Results of a randomized controlled trial after one year.

In 30 seconds

This randomized controlled trial examined a self-directed workbook, with or without one motivational interview (MI), for Canadian adults with cannabis use disorder (CUD), comparing both approaches with delayed workbook treatment. At 9- and 12-month follow-up, outcomes improved across the sample. Adding MI was associated with quicker reductions in cannabis-use quantity, but not frequency or cannabis-related problems, compared with workbook-only and delayed-treatment groups. Workbook-only treatment did not show greater improvement than delayed treatment, although the study was underpowered to detect modest effects. The findings support sustained benefit from low-intensity bibliotherapy when paired with brief MI.

Key findings

• Across the sample, cannabis use, distress, quality of life, and cannabis-related problems improved over time.
• MI was associated with quicker reductions in cannabis-use quantity, but not frequency or cannabis-related problems, versus workbook-only and delayed treatment.
• Workbook-only treatment did not produce greater improvements than delayed treatment; the study was underpowered to detect modest effects.
• Concurrent treatment was accessed by 72% of participants and was not associated with outcomes.

Why it matters

Self-directed support may offer an option for people with CUD who prefer limited professional contact. The results suggest that a brief motivational interview may add benefit for reducing cannabis-use quantity over time, while the workbook alone did not outperform delayed treatment. This distinction is relevant when considering low-intensity approaches within stepped-care models, though the evidence does not establish the workbook’s independent effectiveness.

What to keep in mind

The study was underpowered to detect modest effects. The follow-up sample was 77% White, which may limit how broadly the findings apply.