The AI participants were recruited from the local San Diego community for larger studies investigating risk factors for substance dependence. These individuals were recruited from eight geographically contiguous reservations with a total population of about 4,000 individuals, as described previously (Ehlers et al., 2004a; Ehlers et al., 2004b). Based on the aims of the larger studies, AI participants were excluded if they were pregnant, nursing, or currently had a major medical disorder that precluded them traveling to the research site. Participants were asked to refrain from alcohol or recreational drug use for 24 hours prior to testing, and their breathalyzer blood alcohol levels had to be 0.00 g/dl to be included in the study. The EA and AA participants were selected for the Collaborative Study on the Genetics of Alcoholism (COGA) at seven sites across the United States including Farmington, CT., Indianapolis, Iowa City, New York City, San Diego, St. Louis, and the greater Washington DC area. Individuals who identified their ethnicity as Hispanic or Asian were not included in the analyses due to insufficient numbers of individuals in the datasets.
