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 illicit substances (other than marijuana), verified by toxicology screening, and (5) no DSM-IV abuse or dependence on any illicit substance (including marijuana) in the past 12 months. Subjects were instructed to refrain from drinking alcohol at least 24 hours prior to their scan time, which was verified by a Breathalyzer test (Dräger, Telford, PA).
