Mechanisms of change within motivational interviewing in relation to health behaviors outcomes: A systematic review

Objective: Motivational interviewing (MI) has been identified as an effective treatment for health behaviors. Understanding the mechanisms of MI could have practical implications for MI delivery. This review is the first to examine mechanisms within MI that affect health behavior outcomes and summarizes and evaluates the evidence. Methods: A systematic literature search was conducted in PSYCHINFO, MEDLINE and EMBASE to identify studies that delivered individual MI in the context of health behaviors, excluding addictions, and investigated mechanisms of MI. Effect sizes were calculated. Results: 291 studies were identified and 37 met the inclusion criteria. Few of the 37 studies included, conducted mediation analyses. MI spirit and motivation were the most promising mechanisms of MI. Although self-efficacy was the most researched, it was not identified as a mechanism of MI. Study quality was generally poor. Conclusion: Although this review has indicated possible mechanisms by which MI could influence health behavior outcomes, it also highlights that more high quality research is needed, looking at other possible mechanisms or causal pathways within health behavior outcomes. Practice implications: MI spirit possibly plays an important role within MI and may potentially be used to evoke change talk which links to outcomes.