Consequently, we would expect the Uhl quit success score to influence age of first marijuana use, since first, like tobacco, marijuana activates the brain’s reward system (Covey, Wenzel, & Cheer, 2015; Vlachou & Panagis, 2014; Lupica, Riegel, & Hoffman, 2004). More specifically, it is thought that marijuana’s psychoactive constituent, Δ-THC, may activate CB1 cannabinoid receptors in the brain’s reward circuitry. Second, we found evidence that the quit success score was related to the course of early use of marijuana in adolescence (Musci et al., 2015b). Third, we also found evidence that the greater the number of friend’s who used marijuana, the greater the frequency of marijuana use over the course of adolescence (Musci et al., 2015b).
