Integrating the theory of planned behaviour and self‐determination theory in health behaviour: A meta‐analysis

A literature search identified 36 integrated studies providing 45 tests of effects between TPB and SDT variables. Hunter and Schmidt's (1994) methods of meta-analysis were used to correct the effect sizes across the studies for statistical artifacts. Age (old versus young), publication status (published versus unpublished), study design (correlational versus experimental/intervention), and behaviour type (physical activity versus other health-related behaviours) were evaluated as moderators of the effects. A path-analysis using the meta-analytically derived correlations was conducted to examine the proposed motivational sequence.

Statistically significant corrected correlations were evident among the perceived autonomy support and self-determined motivation constructs from SDT and the attitude, subjective norms, perceived behavioural control, intention, and health-related behaviour constructs from the TPB. Only six of the 28 effect sizes were moderated by the proposed moderators. Path analysis revealed that the significant effects of self-determined motivation on intentions and behaviour were partially mediated by the proximal predictors from the TPB.