A Metaanalysis of Motivational Interviewing: Twenty Five Years of Empirical Studies

Document Type

Article

Journal/Book Title

Research on Social Work Practice

Publication Date

2010

Publisher

SAGE

Volume

20

Issue

2

First Page

137

Last Page

160

Abstract

Objective: The authors investigated the unique contribution motivational interviewing (MI) has on counseling outcomes and how MI compares with other interventions. Method: A total of 119 studies were subjected to a meta-analysis. Targeted outcomes included substance use (tobacco, alcohol, drugs, marijuana), health-related behaviors (diet, exercise, safe sex), gambling, and engagement in treatment variables. Results: Judged against weak comparison groups, MI produced statistically significant, durable results in the small effect range (average g ¼ 0.28). Judged against specific treatments, MI produced nonsignificant results (average g ¼ 0.09). MI was robust across many moderators, although feedback (Motivational Enhancement Therapy [MET]), delivery time, manualization, delivery mode (group vs. individual), and ethnicity moderated outcomes. Conclusions: MI contributes to counseling efforts, and results are influenced by participant and delivery factors.

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