We have observed a consistent contribution of variation within the DRD2, OPRM1, OPRD1, and BDNF genes towards the development of opioid dependence, where these particular genes encode receptors and signaling molecules which play important roles in the pathophysiology of substance use disorders. Despite the strong genetic susceptibility to opioid dependence, environmental factors play an important role in this disorder in keeping with many common disorders of multifactorial etiology. Therefore studies investigating the interactions between genes and the environment will add further to our understanding of opioid and other substances use disorders.
