Beliefs about the risks of smoking mediate the relationship between exposure to smoking and smoking

Objective: Peer and family smoking are key predictors of adolescent smoking. Yet, it is unclear whether the effect of these variables is direct or indirect through the effects of mediating mechanisms. One possible mechanism is smoking risk beliefs. We hypothesized an indirect effect such that exposure to peer and family smoking may affect adolescents' smoking through two sets of risk beliefs; beliefs about the personal harm of smoking, and beliefs about the general immediate harm of smoking, and these beliefs may in turn affect smoking. Methods: Our sample was 963 participants taking part in a longitudinal study of the biobehavioral determinants of smoking. We measured exposure to peer and household smoking in grade 10, smoking risk beliefs in grade 11, and modeled the effects of these variables prospectively on smoking one year post high school graduation in a Structural Equation Model (SEM). Results: Beliefs about the personal harm and general immediate harm of smoking had significant and negative direct effects on smoking one year post high school. However, controlling for 10th grade smoking, only personal harm beliefs mediated the relationship between household smoking exposure and smoking behavior. Specifically, personal harm beliefs mediated the effect of having a household member who smokes on smoking one year post high school graduation. Conclusions: The findings are consistent with the hypothesized mediation model and suggest that exposure to household smoking may affect adolescent smoking through its effects on beliefs about the personal harm of smoking, beyond the effects of previous smoking.