Symptoms of AD were assessed by the CIDI-SF with a section that began by asking respondents the largest number of drinks they ever consumed in 24 hours. Those who responded “never drank” (n=498) were considered lifetime abstainers and excluded from subsequent analyses. Subjects who reported consuming 4 or more drinks in a day were then asked 7 questions which assessed craving for alcohol, DSM-IV criterion A2 for alcohol abuse (dangerous use) and criteria 1 (tolerance), 3 (loss of control), 5 (“great deal of time…”), 6 (activities given up), and 7 (use despite knowledge of harm) for AD. All items were binary except those assessing loss of control and activities given up which had 5 possible responses. The interview skipped these questions for individuals who responded that the most they ever consumed in a day was 1 to 3 drinks (n=1,030). We assumed that these individuals were “light social drinkers” and included them in our analysis with a score of zero for the number of alcohol-related symptoms. We derived factor scores on the total number of individuals with both phenotypic and genotypic data, (3,169 individuals: 2,357 EA and 812 AA).
