As noted in the introduction, our rationale for examining Uhl et al. (2010)’s quit success score in relation to age of first marijuana use was largely driven by our theory of the interplay between the CC intervention and Uhl et al.’s score in delaying onset of first tobacco use (Musci et al., 2015a). As we know from Haberstick, Zieger, et al. (2011), there are likely common and specific, or unique, genetic influences on substance use. In Musci et al. (2015a), we posited a unique genetic influence might best explain the gene × intervention interaction that we found with respect to age of first tobacco use. More specifically, we posit that the quit success score may serve in part as measure of shared genetic liability for substance use as well as the tendency to experience the reinforcing effects of nicotine and that the effect of the classroom-centered intervention on age of first cigarette smoked may have varied as a function of this genetic propensity. The fundamental nature of polygenic scores are such that they do not explicitly test specific biological mechanisms;
