The hazard ratios for the association between genotype and age at first symptom of alcohol dependence were computed in a univariate model and then, in a model that adjusted for sex as well as an interaction between sex and genotype. Genotypes that were significantly associated with alcohol dependence symptoms in QTDT analyses (rs279858 and rs279845) were selected for the survival analyses. For the first series of analyses (Models 1−3), genotype was coded as 0 (no copies of risk allele from QTDT), 1 (1 copy of risk allele from QTDT) and 2 (2 copies of risk allele from QTDT). In a second series of analyses (Models 4−6), genotype was coded under a dominance model as 0 (no copies) and 1 (1 or 2 copies of risk allele). In models 1 and 4, only genotype, coded as 0, 1, 2 and 0,1 respectively, was entered into the model. In models 2 and 5, both genotype and sex were included while in models 3 and 6, the effects of genotype, sex and genotype*sex were examined.
