2024

Hagger, Martin S.; Hamilton, Kyra

In a meta-analysis of longitudinal analyses of the theory of planned behaviour, we tested a series of extended or auxiliary theory-consistent hypotheses: construct stability, theory predictions within and between occasions, consistency over time or stationarity in theory effects and reciprocal effects among constructs. We also tested the effects of moderators on theory effects: measurement lag, health behaviour type (protection, risk) and specific health behaviours (alcohol, dietary and physical activity). A systematic search identified 87 studies eligible for inclusion. Meta-analytic structural equation models supported construct stability and theory effects within and between occasions. Only the perceived behavioural control–intention effect exhibited stationarity. We found little evidence of reciprocal effects, and theory effects were small after accounting for reciprocal effects. We observed theory-consistent effects for the behaviour-type moderators, but no variation in model effects for the measurement lag moderators. Findings advance knowledge of the correlates of intentional behaviour and associated processes over time.