In comparing the entire sample with the subsample, the CHRM2 effects are greater in the illicit drug use subsample than in the sample as a whole. In particular, restricting the sample to those most genetically vulnerable enables two more SNPs to become significant at the 0.05 level. If the risk of the onset of alcohol dependence as a function of genotype were as great in the drug non-users as in the illicit drug use subsample, and taking into account the lower rate of regular alcohol use in the drug non-users, there would be almost twice as many alcohol dependent subjects among the drug non-users as in fact there are.
