The Indirect Effect of Cigarette Smoking on e-Cigarette Progression via Substitution Beliefs.

Purpose: This study sought to evaluate whether associations between adolescent combustible cigarette smoking and e-cigarette progression were explained by beliefs that e-cigarettes substitute for cigarettes in nonsmoking situations.

Methods: Adolescents (N = 1,799) from public high schools outside of Philadelphia, PA, completed in-classroom surveys at wave 1 (fall 2016, beginning of ninth grade) and at 6-month intervals for the following 36 months (fall 2019, beginning of 12th grade).

Results: A parallel process latent growth curve model revealed that the pathway from baseline smoking to e-cigarette use trend through baseline e-cigarette substitution beliefs was significant (B = .02, z = 2.16, p = .03), indicating that the positive effect of greater baseline cigarette smoking on the rate of e-cigarette progression was channeled through e-cigarette substitution beliefs. The indirect effect from baseline smoking to e-cigarette use trend via e-cigarette substitution beliefs trend was also significant, albeit negative (B = -.05, z = -2.61, p = .009). The negative indirect effect suggested that the strong positive effect of baseline cigarette smoking on baseline substitution beliefs was followed by a slowing of the overall rate of change from baseline. Given that the total effect from baseline smoking to e-cigarette trend was not significant (p = .91), the results suggested complete mediation.

Conclusions: Among adolescents with greater use of combustible cigarettes, beliefs regarding the substitutability of e-cigarettes in nonsmoking situations appear to foster progression in e-cigarette use. Addressing these beliefs in the school setting and through media campaign messaging early in adolescence may help to prevent the use of e-cigarettes and combustible cigarettes.