Progress on theory of planned behavior research: advances in research synthesis and agenda for future research

The theory of planned behavior is a social cognition theory that has been widely applied to identify the psychological determinants of intentions and behavior in health contexts. Our 2015 meta-analysis of theory applications in chronic illness contributed to a burgeoning evidence base comprising syntheses supporting theory predictions in health behavior. In this review, we identify limitations of prior meta-analyses of theory applications in health behavior and highlight salient evidence gaps, summarize how recent meta-analyses of the theory have addressed some of the limitations, outline outstanding research questions, and suggest future research syntheses, including those currently in progress, to resolve them. We point to recent and ongoing meta-analyses addressing theory hypotheses and assumptions not tested in previous syntheses, such as perceived behavioral control moderating effects and indirect effects of environmental (e.g., sociostructural variables) and intrapersonal (e.g., personality traits) determinants on health behavior mediated by theory constructs. We also highlight meta-analyses examining behavioral effects of constructs representing extended processes (e.g., habit, implicit cognition) in the context of the theory. Further, we summarize recent meta-analyses addressing directional and causal inferences in theory effects, including meta-analyses of longitudinal studies and experimental and intervention research. We also highlight attempts to test the mechanisms of action of interventions based on the theory including the change meta-analysis method and mediation analyses. We conclude by summarizing the advances that recent meta-analyses of the theory have made to the evidence base of health behavior determinants and interventions and highlighting suggestions for meta-analyses that will further progress the evidence base.