Predicting initiation of smoking in adolescents: evidence for integrating the stages of change and susceptibility to smoking constructs.

We examined the concurrent and predictive validity of stages of change and susceptibility to smoking with respect to smoking onset among adolescents. We also sought to determine whether concurrent use of the two constructs, in the form of an integrated stage/susceptibility index, would predict adolescent smoking acquisition better than eithe r construct alone. Data were examinedfrom two study populations: a prospective study of 1,124 elementary-school through senior-high-school students and a cross-sectional study of 5,624 high-school students. Both constructs demonstrated good concurrent and predictive validity. A measure integrating the stages of smoking acquisition and susceptibility to smoking constructs was created by dividing the precontemplation group as a function of susceptibility. This new classification system yielded better concurrent and predictive validity than did either stage of smoking acquisition or susceptibility to smoking alone.