We first addressed this question by examining the pattern of mHRs in 9 age groups in unrelated members of the general population and in half-siblings, full-siblings, and MZ twins discordant for AUD. In the younger age groups (ie, those <40 years), mHRs (1)were much greater in the general population than in the discordant relative pairs, (2) became progressively smaller in more closely related individuals, and (3) did not differ from unity in discordant MZ twins. This is the pattern expected for strong familial confounding. That is, the association between AUD and excess mortality in these age groups would appear to result largely from shared familial factors rather than the direct effects of AUD itself. These factors might include personality traits, such as impulsivity or novelty seeking, or a proclivity toward other substance use or misuse, which are both associated with AUD22,23 and under genetic influence.24,25
