As detailed in Tables S1 and S2 in the data supplement that accompanies the online edition of this article, we identified, in men and in women respectively, the following number of unique same-sex sibling pairs discordant for both the occurrence of or age at marriage and the occurrence of or age at first registration for alcohol use disorder: cousins, 21,849 and 6,599; half siblings, 1,519 and 487; full siblings, 7,250 and 2,388; and monozygotic twins, 100 and 26. As seen in Table 4, within-pair analyses demonstrated no evidence in either men or women for an attenuation of the association between marital status and alcohol use disorder with increased sharing of genetic and environmental background. Although known imprecisely, the association seen with risk for alcohol use disorder in monozygotic twin pairs discordant for marital status was slightly stronger than that seen in the general population; for men the hazard ratio was 0.31 (95% CI=0.11–0.85) and for women 0.18 (95% CI=0.04–0.82). Perhaps more importantly, in our large sample of discordant full siblings, the observed associations were very similar to those seen in the population, where for men the hazard ratio is 0.36 (95% CI=0.33–0.39) and women 0.25 (95% CI=0.21–0.30).
