Participants were non-treatment seeking problem drinkers recruited from the Los Angeles community through flyers and online advertisements as part of a larger study to investigate the effect of the OPRM1 gene on subjective responses to alcoho1 (15). The protocol was approved by the University of California, Los Angeles Institutional Review Board, and following consenting procedures, 295 participants were screened for alcohol dependence and prospectively genotyped. Of those screened, 43 alcohol dependent individuals were selected to undergo the randomized, placebo-controlled, alcohol administration (the primary aim of the parent study), which included similar numbers of participants with and without the minor (G) allele of the OPRM1 gene (AA, n = 23 and AG/GG, n = 20) (15). A subsample of 20 alcohol dependent individuals was then selected from this sample for the MRI portion of the study (AA, n=10; AG/GG, n=10). Ethnicity was matched across groups in this subsample to account for population stratification at the OPRM1 locus. Inclusion criteria were: (1) ages 21 to 55 years, (2) current DSM-IV alcohol dependence, (3) no major psychiatric disorders, (4) no current use of
