In the illicit drug use subsample in the youngest age range, CHRM2 is a greater factor for the onset of alcohol dependence than in the entire sample. However, EROs are not a factor in the onset of alcohol dependence in this group. The range of ERO values in the illicit drug use subsample does not differentiate those who become alcohol dependent from those who do not, although ERO values differentiate the illicit drug subsample from their complement in the entire sample. The illicit drug use sample shows greater and more extensive genetic effects than the entire sample, since the result of selecting the illicit drug use subsample is to remove those subjects whose alcohol dependence is unlikely to be genetically affected from the analysis.
