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

INTRODUCTION: Self-directed interventions may help close treatment gaps in cannabis use disorder (CUD), particularly for individuals who prefer minimal professional contact. We previously tested a paper-and-pencil workbook, with or without a single motivational interview (MI), in a three-arm randomized controlled trial. METHODS: Canadian adults with CUD were allocated to workbook plus MI (WMI), workbook only (WB), or delayed workbook treatment (DT). The current paper reports outcomes after 9 and 12 months as well as exploratory analyses on workbook usage. Trial outcomes included days and grams of cannabis use in the past month, distress, quality of life, and cannabis-related problems. RESULTS: The follow-up sample (N = 155) was 77% White and 54% female with a mean age of 32.1 years. Across the sample, all outcomes improved over time. However, the MI conferred additional benefit in terms of quicker reductions in cannabis use quantity, but not frequency or cannabis-related problems, relative to WB and DT. WB did not demonstrate greater improvements than DT, although the study was underpowered to detect modest effects. Concurrent treatment was accessed by 72% but not associated with outcomes. Engagement with the workbook declined over the follow-ups, although a meaningful subset continued regular use. Perceived workbook helpfulness correlated with perceived treatment success (r = 0.33). Within the WMI group, MI non-completers reported higher workbook frequency than completers, suggesting possible compensation for the missed MI. CONCLUSIONS: Results support the durability of low-intensity, self-directed bibliotherapy for CUD when combined with a brief MI. These findings point to stepped-care applications while motivating research on mechanisms, subgroups, and engagement.