title: Combinations of techniques that effectively change health behavior: evidence from Meta-CART analysis.
abstract: OBJECTIVE
  Many health-promoting interventions combine multiple behavior change techniques (BCTs) to maximize effectiveness. Although, in theory, BCTs can amplify each other, the available meta-analyses have not been able to identify specific combinations of techniques that provide synergistic effects. This study overcomes some of the shortcomings in the current methodology by applying classification and regression trees (CART) to meta-analytic data in a special way, referred to as Meta-CART. The aim was to identify particular combinations of BCTs that explain intervention success.
  
  
  METHODS
  A reanalysis of data from Michie, Abraham, Whittington, McAteer, and Gupta (2009) was performed. These data included effect sizes from 122 interventions targeted at physical activity and healthy eating, and the coding of the interventions into 26 BCTs. A CART analysis was performed using the BCTs as predictors and treatment success (i.e., effect size) as outcome. A subgroup meta-analysis using a mixed effects model was performed to compare the treatment effect in the subgroups found by CART.
  
  
  RESULTS
  Meta-CART identified the following most effective combinations: Provide information about behavior-health link with Prompt intention formation (mean effect size ḡ = 0.46), and Provide information about behavior-health link with Provide information on consequences and Use of follow-up prompts (ḡ = 0.44). Least effective interventions were those using Provide feedback on performance without using Provide instruction (ḡ = 0.05).
  
  
  CONCLUSIONS
  Specific combinations of BCTs increase the likelihood of achieving change in health behavior, whereas other combinations decrease this likelihood. Meta-CART successfully identified these combinations and thus provides a viable methodology in the context of meta-analysis.
authors.affiliation: Expertise Group Life Style, Netherlands Organization for Applied Scientific Research (TNO).
authors.forename: Elise
authors.initials: E
authors.lastname: Dusseldorp
authors.affiliation: Expertise Group Life Style, Netherlands Organization for Applied Scientific Research (TNO).
authors.forename: Lenneke
authors.initials: L
authors.lastname: van Genugten
authors.affiliation: Expertise Group Life Style, Netherlands Organization for Applied Scientific Research (TNO).
authors.forename: Stef
authors.initials: S
authors.lastname: van Buuren
authors.affiliation: Expertise Group Life Style, Netherlands Organization for Applied Scientific Research.
authors.forename: Marieke W
authors.initials: MW
authors.lastname: Verheijden
authors.affiliation: Expertise Group Life Style, Netherlands Organization for Applied Scientific Research.
authors.forename: Pepijn
authors.initials: P
authors.lastname: van Empelen
mesh_terms: D001521:Behavior Therapy / Q000379:methods*; D015438:Health Behavior; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D012044:Regression Analysis; D016896:Treatment Outcome