The Theory of Planned Behavior and Adolescent Marijuana Use: Examining the Moderating Effects of Cigarette and E-cigarette Co-use

Background: This study examines the moderating effects of cigarette and e-cigarette co-use on the relationship between adolescent intention to use and marijuana use using the Theory of Planned Behavior (TPB). Method: A total of 217,276 adolescents in grades 6, 8, 10, and 12 were assessed using data from a large statewide surveillance dataset of youth self-report of substance use and related risk and protective factors. Structural Equation Models consisting of latent variables representing behavioral, normative, and control beliefs were regressed on intention to use and past 30-day marijuana use. Tests of moderation of the pathways between intention and marijuana use were used to test hypotheses, and grade level, gender, and race were included as covariates. Results: The overall model fit of the TPB predicting adolescent marijuana use provided good fit to the data (χ²(127) = 58042, p < 0.01, CFI = 0.95, TLI = 0.94, RMSEA = 0.04, SRMR = 0.03). After controlling for features of the model that may serve as common liability to substance use, past 30-day cigarette use moderated the relationship between intention and marijuana use (β = 0.46, p <.001). A stronger moderating effect was observed with past 30-day e-cigarette use (β = 0.63, p <.001). Past 12-month nicotine vaping (β = 0.44, p <.001) and flavor-only vaping (β = 0.30, p <.001) strengthened the relationship between intention and marijuana use. Conclusion: Adolescent marijuana use prevention may be enhanced by targeting general inhalation behaviors and restricting access to cigarettes, e-cigarettes, and flavor-only vaping products.