Motivational Interviewing Informed Interventions for Problem Gambling and Gambling Disorder: A Systematic Review and Meta-Analysis

Aims: To conduct a systematic review of motivational interviewing (MI) integrity in randomized controlled trials and update the effect size estimate of MI informed interventions compared to control conditions on gambling behavior and gambling disorder symptom severity at posttreatment and follow-up. Method: Five databases were searched to identify published and unpublished studies of randomized controlled trials. Studies randomizing participants to a MI informed intervention or a control condition that did not receive MI were eligible. A random effects meta-analysis of Hedges’s g effect sizes representing outcomes of MI informed interventions versus control at posttreatment and follow-up was conducted. Results: Seven studies representing 796 participants were identified. MI informed interventions varied greatly in their descriptions, and no intervention met the proposed criteria for establishing MI integrity in clinical trials (Miller & Rollnick, 2014). Outcomes between conditions were almost equivalent for gambling frequency (g = -0.04), gambling expenditure (g = -0.03), and gambling disorder symptom severity (g = 0.01) at posttreatment. Similarly, there was almost no difference in each outcome at follow-up (g’s = -0.02, -0.02, and -0.10). Conclusions: The findings indicated that no randomized controlled trials have established MI integrity among individuals with problem gambling and gambling disorder. Furthermore, the previous effect size estimates of MI informed interventions were overestimated due to the inclusion of trials that combined MI informed interventions with cognitive-behavioral workbooks. Future research will require objective fidelity monitoring to ensure adherence to MI and use study designs that isolate the effect of motivational interventions on outcomes.