In a recent association study of heroin addiction we have detected association of two variants in intron 1 (rs510769 and rs3778151) in European Americans.9 Of note, the “addiction-focused” array28 used in this study does not include OPRM1 SNPs upstream of exon 1. These results are supported by two studies in which intron 1 SNPs showed association with drug dependence in European Americans,29 or with positive response to heroin after first use in Chinese.30 We did not find a similar association in an African American cohort.31 A 10K genome-wide association study of a subset of the same cohort from our laboratory identified association of a SNP rs1074287, located 11.6 kb upstream of exon 1, with heroin addiction.32
