Logistic regression analysis using a mixed model to control for the relatedness of subjects within families was used to investigate the association between copy number genotype and level of response to alcohol. Copy number had little effect on the level of response to alcohol. The presence of at least one copy of a relatively rare allele for several SNPs is associated with a more intense response to alcohol. The best evidence for association was found for the first three markers, which lie near the beginning of the gene near the promoter region, when considering genotype alone. The SNP rs10776687 showed the greatest evidence for association with a p value of 0.007 and was able to explain 4.6% of the variance of the SHAS score phenotype (r2=0.046). In this case, copy number was ignored and all genotypes were assigned as biallelic. When considering copy number and genotype together, none of the markers were significant. Copy number alone (1, 2, or 3) was not significantly associated. Interestingly, when modeling the effect of genotype and copy number on the number of cigarettes smoked
