larger studies included Zhang et al.’s study, which examined 1063 European American individuals with 620 cases of substance dependence [12], and Hou et al.’s study of 1030 Han Chinese males with 500 cases of opioid dependence [64]. The results from both of these studies suggested a significant association between specific SNPs and opioid dependence in two ethnic groups, however further large studies are needed to clarify the role of these common SNPs in opioid dependence. Nonetheless, the reviewed studies provide significant evidence for the genetic contribution to addiction disorders, and detailed investigations into the effects of these genes on the pathophysiology and metabolism of opioids will provide further clues into the etiology of such disorders. Ultimately, such information could aid in the identification of individuals at risk of developing opioid dependence and better treatment for individuals already affected with the disease.
