of substance use liability) that implicated several genomic regions, including chromosomes 3q24-25 (near markers D3S1279 and D3S1614) and 9q34 (near markers D9S1826 and D9S1838). A 2008 study58 reported SNP association results from a targeted gene assay designed to test 50 candidate genes with previous associations with substance use disorders and conduct disorder, in a sample of male probands in treatment of antisocial drug dependence and a matched set of community controls. After gene-based permutation tests, 2 genes probed with multiple SNPs (OPRM1 and CHRNA2) emerged as plausible candidates for a role in antisocial drug dependence. Other studies have focused on candidate genes, such as the neuronal nicotinic acetylcholine receptors and tobacco and alcohol phenotypes. Ehringer and colleagues59 examined 2 neuronal nicotinic receptor subunit candidate genes, and found that CHRNA4 was associated with past 6-month use of alcohol in White, and CHRNB2 was associated with the initial subjective response to alcohol and tobacco.
