Predicting smoking reduction among adolescents using an extended version of the theory of planned behaviour

This study tested the ability of the theory of planned behaviour (TPB) to predict adolescents' intentions to reduce smoking and the subsequent behaviour one year later. In addition, past behaviour, moral norms, self-identity as a smoker, group identification, group norms and action planning were assessed. A prospective sample of 145 adolescents (M = 14 years, Time 1) participated in the study. The TPB provided good predictions of intentions (adjusted R2 = 0.28). An extended TPB model including self-identity, moral norms, and the group identification group norm interaction accounted for 39% (adjusted R2) of the variance in intentions. The TPB components did not have a direct impact on subsequent behaviour, while past behaviour and the perceived behavioural control intention interaction accounted for 35% of the variance in behaviour after one year. The practical implications of these results for the development of interventions to encourage adolescent smokers to reduce or quit smoking are outlined.