The gene coding for the dopamine receptor D2 (DRD2) could be involved in heroin dependence and other SUD as a nonspecific genetic factor, because opioids and other substances of abuse induce some of their rewarding effects through the mesolimbic dopamine system [5,6]. Preclinical research supports this hypothesis. An absence of opioid-rewarding effects has been reported in mice lacking DRD2 [7].
