The current investigation examines whether OPRM1, OPRD1, and OPRK1 SNPs are associated with risk for heroin dependence in a very large Australian sample of cases (N=1459) receiving maintenance treatment for heroin dependence in New South Wales (NSW) and non-dependent controls (N=1495 unrelated individuals) ascertained from samples of twins and family members as not meeting DSM-IV criteria for lifetime alcohol or illicit drug dependence. The substantially larger sample size provides an opportunity to investigate more definitively the involvement of these genes. Cases are also compared to a second control group (N=531), termed neighborhood controls, ascertained from economically-disadvantaged neighborhoods in close proximity to maintenance clinics. Because these individuals have higher rates of lifetime drug use and nicotine, alcohol, and non-opioid illicit drug dependence, this comparison can provide insight into the degree to which association findings are specific for heroin dependence or shared with other addiction phenotypes.
