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; but offer an explanation to the genetic liability of a particular behavior (Maher, 2015). One could posit that biological pathways related to novelty seeking and reward circuitry may play a large role in the common genetic liability of substances; with substance specific pathways also playing a role. The exact mechanism through which the polygenic score is impacting substance use behavior is unknown, and likely we would see associations between this polygenic score and a number of behaviors related to novelty or sensation seeking. Ultimately proof of our theory of the mechanism underlying the polygenic score × intervention interaction found in the present study and Musci et al. (2015a) will require a thorough investigation of the biological functions of each of the SNPs making up the quit success score.
