Prevailing theories postulate that addiction vulnerability is linked to impairment of reward sensitivity and/or inhibitory control. Recently, genetic polymorphisms have been used to dissect potential striatal dopamine-receptor involvement in decision-making in relation to positive and negative reinforcement outcomes [18], [19], [32]. Our data supports an association of the DRD2 SNP rs6277 with negative reward performance, but not for other DRD2 SNPs studied. Other investigations [32] have also indicated a differential effect of the DRD2 SNPs on behavior that may relate to the role of these SNPs in modulating DRD2 functions (i.e., DRD2 binding, density). The ability to replicate previous studies of the DRD2 rs6277 SNP with avoidance learning emphasizes the validity of our study population. Moreover, the overall lack of association between reinforcement learning and inhibitory control to cannabis dependence either directly or as mediators suggest that although these behavioral traits are important to various aspects of addiction, they do not appear to contribute to cannabis-dependence vulnerability to the same extent as negative emotional traits.
