Males between the ages of 18 and 25 years were recruited using a combination of venue-based method and a respondent-driven procedure that has been described elsewhere (Ehlers et al., 1998a). Following telephone screening with research staff to complete a questionnaire (Schuckit, 1984; Schuckit and Gold, 1988) that was used to select individuals who met eligibility for the study; all subjects signed informed consent, and the study was approved by The Scripps Research Institute Internal Review Board and Indian Health Council. Participants were excluded from further evaluation if they met diagnostic criteria for alcohol or other substance dependence, or other major Axis I psychiatric disorders according to criteria outlined in the Third Diagnostic and Statistical Manual Disorders (DSM-III) (American Psychiatric Association, 1980). Individuals were also excluded from this study if they were taking prescribed medication, had any major medical condition, had never drank alcohol, or had abstained from alcohol over the previous 6 months.
