The mu opioid receptor has a clear involvement in mediating the analgesic and rewarding effects of endogenous and exogenous opioids, and has been tightly linked to the development of addiction disorders due to its involvement in the brain reward pathway.1,8,9 The OPRM1 gene encodes for the mu opioid receptor, and sequence variants within its coding region are the most frequently studied candidates in association with opioid dependence.9 However, to date no definitive conclusion has been reached regarding the role of OPRM1 polymorphisms in determining susceptibility to opioid dependence.5,9
