Using an extended version of the theory of planned behaviour to predict smoking cessation in two age groups

Abstract

The aim of this study was twofold: (i) to test the utility of the theory of planned behaviour (TPB) in predicting intentions to quit smoking and subsequent behaviour in two age groups, and among women and men, and (ii) to examine whether descriptive norms, moral norms and past behaviour predict intentions and behaviour beyond the impact of the TPB components. Analyses were based on data from a prospective sample of 447 daily smokers (adolescents 16–19 years, n = 174, M = 17.5, adults 35–55 years, n = 311, M = 44 years). The TPB accounted for 31.8% and 38% of the variance in intentions in the adolescent and adult groups, respectively. The extension variables added 12.6% and 12.1% to the explained variance of intentions in the adolescent and adult groups. Affective attitude was the strongest predictor of intentions in both age groups. A number of moderating effects of gender and age were found in predicting intentions. Moreover, intentions and perceived behavioural control (PBC) had a direct impact on behaviour only in the adult group, while the PBC × intention interaction was a significant predictor in the adolescent group. The extended TPB model provided a better fit among the adults than among adolescents (Nagelkerke R2 = 0.29 vs. 0.17, respectively).