OPRK1 and substance dependence: Genotype data for 13 OPRM1 Single Nucleotide Polymorphisms (SNPs), 11 OPRD1 SNPs and seven OPRK1 SNPs were obtained from 382 European Americans (EAs) affected with substance dependence [among them, 318 with Alcohol Dependence (AD), 171 with Cocaine Dependence (CD), and 91 with Opioid Dependence (OD)] and 338 EA control subjects.