How Effective are Behavior Change Interventions Based on the Theory of Planned Behavior? A Three-Level Meta-Analysis

The theory of planned behavior (TPB) is a prominent framework for predicting and explaining behavior in a variety of domains. The theory is also increasingly being used as a framework for conducting behavior change interventions. In this meta-analysis, we identified 82 papers reporting results of 123 interventions in a variety of disciplines. Our analysis confirmed the effectiveness of TPB-based interventions, with a mean effect size of .50 for changes in behavior and effect sizes ranging from .14 to .68 for changes in antecedent variables (behavioral, normative, and control beliefs, attitude, subjective norm, perceived behavioral control, and intention). Further analyses revealed that the interventions' effectiveness varied for the diverse behavior change methods. In addition, interventions conducted in public and with groups were more successful than interventions in private locations or focusing on individuals. Finally, we identified gender and education as well as behavioral domain as moderators of the interventions' effectiveness.