title: Mechanisms of change within motivational interviewing in relation to health behaviors outcomes: a systematic review.
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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  MI spirit possibly plays an important role within MI and may potentially be used to evoke change talk which links to outcomes.
authors.affiliation: Institute of Primary Care & Public Health, Cardiff University School of Medicine, Cardiff, UK. Electronic address: CopelandLC@cardiff.ac.uk.
authors.forename: Lauren
authors.initials: L
authors.lastname: Copeland
authors.affiliation: South East Wales Trials Unit, Institute of Translation, Innovation, Methodology & Engagement, Cardiff University School of Medicine, Cardiff, UK. Electronic address: McNamara@cardiff.ac.uk.
authors.forename: Rachel
authors.initials: R
authors.lastname: McNamara
authors.affiliation: South East Wales Trials Unit, Institute of Translation, Innovation, Methodology & Engagement, Cardiff University School of Medicine, Cardiff, UK. Electronic address: KelsonMJ@cf.ac.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Kelson
authors.affiliation: South East Wales Trials Unit, Institute of Translation, Innovation, Methodology & Engagement, Cardiff University School of Medicine, Cardiff, UK. Electronic address: SimpsonSA@cf.ac.uk.
authors.forename: Sharon
authors.initials: S
authors.lastname: Simpson
mesh_terms: D001521:Behavior Therapy / Q000379:methods / Q000592:standards*; D003376:Counseling / Q000379:methods / Q000592:standards*; D015438:Health Behavior; D006801:Humans; D062405:Motivational Interviewing; D017063:Outcome Assessment, Health Care; D018802:Patient-Centered Care / Q000379:methods*; D011369:Professional-Patient Relations
keywords: Active ingredients of treatment; Behavior; Counseling; Health care; Mechanisms of change; Mediator; Motivational interviewing; Systematic review; Therapy process