Objective In the present meta-analysis, we test the technical and relational hypotheses of Motivational Interviewing (MI) efficacy. We also propose an a priori conditional process model where heterogeneity of technical path effect sizes should be explained by interpersonal/relational (i.e., empathy, MI Spirit) and intrapersonal (i.e., client treatment seeking status) moderators. Method A systematic review identified k = 58 reports, describing 36 primary studies and 40 effect sizes (N = 3025 participants). Statistical methods calculated the inverse variance-weighted pooled correlation coefficient for the therapist to client and the client to outcome paths across multiple target behaviors (i.e., alcohol use, other drug use, other behavior change). Results Therapist MI-consistent skills were correlated with more client change talk (r = .55, p < .001) as well as more sustain talk (r = .40, p < .001). MI-inconsistent skills were correlated with more sustain talk (r = .16, p < .001), but not change talk. When these indicators were combined into proportions, as recommended in the Motivational Interviewing Skill Code, the overall technical hypothesis was supported. Specifically, proportion MI consistency was related to higher proportion change talk (r = .11, p = .004) and higher proportion change talk was related to reductions in risk behavior at follow up (r = −.16, p < .001). When tested as two independent effects, client change talk was not significant, but sustain talk was positively associated with worse outcome (r = .19, p < .001). Finally, the relational hypothesis was not supported, but heterogeneity in technical hypothesis path effect sizes was partially explained by inter- and intra-personal moderators. Conclusions This meta-analysis provides additional support for the technical hypothesis of MI efficacy; future research on the relational hypothesis should occur in the field rather than in the context of clinical trials.

Objective: This meta-analysis examined 30 randomized controlled trials (32 study sites; 35 study arms) that tested the efficacy of cognitive-behavioral therapy (CBT) for alcohol or other drug use disorders. The study aim was to provide estimates of efficacy against three levels of experimental contrast (i.e., minimal [k = 5]; nonspecific therapy [k = 11]; specific therapy [k = 19]) for consumption frequency and quantity outcomes at early (1 to 6 months [kes = 41]) and late (8+ months [kes = 26]) follow-up time points. When pooled effect sizes were statistically heterogeneous, study-level moderators were examined. Method: The inverse-variance weighted effect size was calculated for each study and pooled under random effects assumptions. Sensitivity analyses included tests of heterogeneity, study influence, and publication bias. Results: CBT in contrast to minimal treatment showed a moderate and significant effect size that was consistent across outcome type and follow-up. When CBT was contrasted with a nonspecific therapy or treatment as usual, treatment effect was statistically significant for consumption frequency and quantity at early, but not late, follow-up. CBT effects in contrast to a specific therapy were consistently nonsignificant across outcomes and follow-up time points. Of 10 pooled effect sizes examined, two showed moderate heterogeneity, but multivariate analyses revealed few systematic predictors of between-study variance. Conclusions: The current meta-analysis shows that CBT is more effective than a no treatment, minimal treatment, or nonspecific control. Consistent with findings on other evidence-based therapies, CBT did not show superior efficacy in contrast to another specific modality.

Objective This study tested mediating processes hypothesized to explain the therapeutic benefit of an efficacious motivational interview (MI). The constructs of interest were motivation to change, cognitive dissonance about current drinking, self-efficacy for change, perceived young adult drinking norms, future drinking intentions, and the use of protective behavioral strategies. Method A randomized controlled trial compared the efficacy of a brief MI to a time- and attention-matched control of meditation and relaxation training for alcohol use. Participants were underage, past-month heavy drinkers recruited from community (i.e., non four-year college or university) settings (N=167; ages 17–20; 58% female; 61% White). Statistical analyses assessed mechanisms of MI effects on follow up (6-week; 3-month) percent heavy drinking days (HDD) and alcohol consequences (AC) with a series of temporally-lagged mediation models. Results MI efficacy for reducing 6-week HDD was mediated by baseline to post-session changes in the following three processes: increasing motivation and self-efficacy, and decreasing the amount these young adults intended to drink in the future. For 6-week AC, MI efficacy was mediated through one process: decreased perceived drinking norms. At 3-month follow up, increased cognitive dissonance mediated HDD, but not AC. Further, increased use of certain protective behavioral strategies (i.e., avoidance of and seeking alternatives to drinking contexts) from baseline to 6-weeks mediated both 3-month HDD and AC. Conclusions Findings suggest that within-session cognitive changes are key mechanisms of MI’s effect on short-term alcohol outcomes among community young adults while protective behaviors may be more operative at subsequent follow up.

This preliminary meta-analysis suggests that aggregate measures of change and sustain talk are comprised of statement subtypes that are not equally meaningful in predicting outcome following MI for addictive behavior change.