We performed secondary analyses exploring the hypothesis that genetic effects are stronger in those alcohol dependent individuals with an earlier age of onset. Association analysis was performed defining as affected only those individuals meeting DSM-IV criteria for alcohol dependence by age 21 (n = 399; Table 1). As in the above analyses of alcohol dependence, 1,025 family members were classified as unaffected. Others, including individuals meeting DSM-IV alcohol dependence criteria at age 22 or older, were considered unknown.
