Inclusion criteria consisted of physically healthy sibling pairs from all ethnic groups aged 21 through 35 years, who were able to read and speak conversational English. Social alcohol drinkers, defined as drinking less than 7 drinks per week (for females) and 14 drinks a week (for males) per guidelines from the National Institutes of Alcohol Abuse and Alcoholism (NIAAA, 2003), were selected to avoid influence of heavy drinking history on the metabolism or responses to alcohol administration during the study. The diagnosis of alcohol dependence was based on a best final diagnosis derived from concurrence of criteria based on: (1) revised Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV; American Psychiatric Association [DSM-IV-TR], 2000), (2) Diagnostic and Statistical Manual of Mental Disorders III (DSMIII-R; American Psychiatric Association, 1987), and (3) International Statistical Classification of Diseases and Related Health Problems-10 (ICD-10; World Health Organization, 1992).
