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

https://doi.org/10.1016/j.pec.2014.11.022Get rights and content

Highlights

  • Systematic review: mechanisms of motivational interviewing and health behavior not addictions.

  • Motivation and MI spirit appear to be the most promising mechanisms of MI.

  • A potential causal chain, including therapist behavior and change talk was found.

  • Mechanisms should be tested via mediation analysis to test the predictive validity.

Abstract

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.

Introduction

Leading causes of death have changed dramatically in the last few decades, shifting from infectious diseases to non-communicable causes [1]. Changing unhealthy lifestyle behaviors is an important issue. A key barrier to behavior change is a lack of motivation [2]. Motivational interviewing (MI) is a counseling approach designed to promote behavior change. It aims to strengthen personal motivation for, and commitment to a specific goal by eliciting and exploring the person's own reasons for change within an atmosphere of acceptance and compassion [3]. There is a lack of evidence for specific mechanisms that may account for its efficacy within health behaviors [4], [5] such as exercise or adhering to a medical regime. Looking at mechanisms of change (mediators) means attempting to understand what it is that brings about change. Understanding how MI works could lead to improvements in practice and efficacy, focus research efforts and further enhance our understanding of behavior change processes [6].

There have been at least 12 reviews that have found statistically significant effects of MI in relation to health outcomes [5], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17]. However, these reviews do not examine the mechanisms of MI. Potential mechanisms relate to counsellors’ skills such as empathy [18], [19], while others relate to client behavior such as change talk [20], [21], [22]. There are potential mediators ‘within the individual’ for example self-efficacy and readiness to change which have also been linked to outcomes within MI (see Section 2 for full list of mechanisms). Few systematic reviews explore mechanisms of MI. One review examining mechanisms of MI and substance abuse found the most consistent evidence pointed to change talk, clients’ experience of discrepancy and therapist MI-inconsistent behaviors as being important [4]. The review however, investigates substance abuse outcomes and not health behaviors. Health behavior outcomes are “behavior patterns, actions and habits that relate to health maintenance, to health restoration and to health improvement” [23]. This includes behaviors such as exercise, diet, weight loss, managing bulimia or anorexia or adhering to a medical regime. These health behaviors may involve different mechanisms [15], [24] as they require the modification or addition of a behavior rather than the termination of a behavior as for addictions [10], [15]. Therefore mechanisms found to be important previously in the addictions field [4] may be different from those found to predict behavior change in these health behaviors. To date there has not been a systematic review looking at health behaviors and mechanisms within MI.

The aim of this review is to systematically review studies identifying possible mechanisms underlying the effectiveness of MI in relation to health behaviors. It will look at mechanisms identified in the MI literature (addictions and health behaviors) to asses if the mechanisms of change in relation to health behaviors are the same or different from those in the addictions field. The review will look at the extent to which MI is associated with a particular mechanism and whether this mechanism is related to health outcomes.

Section snippets

Study eligibility criteria

The papers included within this review must examine all three of these aspects: MI, a mechanism of MI and a health outcome otherwise they will not be included.

Selected studies met the following inclusion criteria:

  • Articles published from 1980 to the present.

  • Participants received MI or an intervention referred to as motivational enhancement therapy (MET), motivational enhancement or brief motivational intervention. These interventions all incorporate the techniques of MI [5]. Throughout this

Study characteristics

The search identified 291 papers, after duplicates were excluded and search limits applied. After screening abstracts using the inclusion and exclusion criteria, 87 papers were obtained in full text. The final number of included studies which includes unpublished studies, and studies obtained from reference lists was 37 (see Fig. 3).

The total numbers of participants included in this systematic review are: RCTs = 4946; non-randomized controlled studies = 316; non-controlled studies = 478;

Discussion

This review highlights that despite statistically significant evidence that MI positively influences health outcomes [5], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], there are few studies looking at the mechanisms of MI. This review shows that there is varying and limited evidence for the different links in the causal chain (Fig. 1). The mechanisms [15], [24] may be different from addictions as mentioned earlier [10], [15], however from the limited number of studies exploring

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