OPRM1 and alcohol drinking: Based on studies of twins and adoption, the hereditary component of alcohol dependence has been estimated at 50%‐60%.1 The endogenous opioid system has been implicated in the development of alcohol dependence due to its prominent role in the central reward mechanism.2 Existing studies suggest that the level of alcohol‐dependent activation in endogenous opioid transmission might be in part genetically determined.3 Among opioid receptor genes, OPRM1 encoding the μ‐opioid receptor is the most intensively studied in relation to drug dependence and alcoholism.