heroin and other illicit drug dependence. The large difference in the strength of association observed in the comparison with non-dependent neighborhood controls (individuals with high exposure to illicit drugs, either via use or from residing in environments with widespread drug availability) versus ATR controls (individuals not dependent on alcohol or illicit drugs, with significantly lower illicit drug exposure) strongly suggests that this liability likely represents risk of dependence contingent on drug exposure. Our findings raise an intriguing possibility that non-dependent highly substance-exposed controls might be particularly informative for attempts to identify polymorphisms associated with drug dependence liability.
