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. A systematic review identified k = 58 reports, describing 36 primary studies and 40 effect sizes (N = 3,025 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). 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 intrapersonal moderators. 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. (PsycINFO Database Record

The technical hypothesis of motivational interviewing (MI) posits that therapist-implemented MI skills are related to client speech regarding behavior change and that client speech predicts client outcome. The current meta-analysis is the first aggregate test of this proposed causal model. A systematic literature review, using stringent inclusion criteria, identified 16 reports describing 12 primary studies. We used review methods to calculate the inverse-variance-weighted pooled correlation coefficient for the therapist-to-client and the client-to-outcome paths across multiple targeted behaviors (i.e., alcohol or illicit drug use, other addictive behaviors). Therapist MI-consistent skills were correlated with more client language in favor of behavior change (i.e., change talk; r = .26, p < .0001), but not less client language against behavior change (i.e., sustain talk; r = .10, p = .09). MI-inconsistent skills were associated with less change talk (r = -.17, p = .001) as well as more sustain talk (r = .07, p = .009). Among these studies, client change talk was not associated with follow-up outcome (r = .06, p = .41), but sustain talk was associated with worse outcome (r = -.24, p = .001). In addition, studies examining composite client language (e.g., an average of negative and positive statements) showed an overall positive relationship with client behavior change (r = .12, p = .006; k = 6). This meta-analysis provides an initial test and partial support for a key causal model of MI efficacy. Recommendations for MI practitioners, clinical supervisors, and process researchers are provided.

Aims: To identify communication characteristics of patients and counsellors during brief alcohol intervention (BAI) which predict changes in alcohol consumption 12 months later. Methods: Tape-recordings of 97 BAI sessions with hazardous drinkers were analysed using the Motivational Interviewing Skill Code (MISC). Outcome measures were (i) baseline to a 12-month difference in the weekly drinking quantity, and (ii) baseline to a 12-month difference in heavy drinking episodes per month. Bivariate analyses were conducted for all MISC measures, and significant variables were included in multiple linear regression models. Results: Patient communication characteristics (ability to change) during BAI significantly predicted the weekly drinking quantity in the multiple linear regression model. There were significant differences for some of the counsellor skills in bivariate analyses but not in the multiple regression model adjusting for patients' talk characteristics. Changes in heavy drinking showed no significant association with patient or counsellor skills in the multiple linear regression model. Conclusion: Findings indicate that the more the patient expresses ability to change during the intervention, the more weekly alcohol use decreases. The role of the counsellor during the interaction, and influence on the outcomes was not clearly established. Implications for BAI and related research are discussed.