Abstract
BACKGROUND: Medical conditions related to alcohol use disorders (AUD) represent a substantial public health concern. However, only a subset of individuals with AUD develop these conditions and the extent to which genetic and environmental factors that are shared with AUD, versus those distinct from it, contribute to this progression has not yet been determined. METHODS: Using data from Swedish national registries for a cohort born from 1932 to 1970 (N = 1,319,214, 48.9% women), we conducted twin-sibling biometric model fitting to examine the genetic and environmental sources of variance that contribute to the liability to alcohol-related medical conditions (AMC). Progression to AMC, determined using medical registry data, was contingent on an AUD registration, which was determined using medical and criminal registry data. RESULTS: We identified AUD registrations in 3.2% of women and 9.2% of men. Among individuals with an AUD registration, 14.4% of women and 15.4% of men had an AMC registration. In the final models, we constrained the beta pathway from AUD to AMC and the genetic and unique environmental paths to be equal across sexes. The beta path was estimated at 0.59. AMC was modestly heritable in women (A = 0.32) and men (A = 0.30). The proportion of total heritability unique to AMC was 39.6% among women and 41.3% among men. A higher proportion of total environmental variance was unique to AMC: 76.7% for women and 77.2% for men. In a sensitivity analysis limited to liver-related AMC, we observed similar results, with a slightly lower beta path from AUD to AMC (0.46) and higher proportions of AMC-specific genetic (70.0% in women; 71.7% in men) and environmental (84.5% in both sexes) variance. CONCLUSIONS: A moderate-to-substantial proportion of genetic and environmental variance that contributes to AMC risk is not shared with AUD, underscoring the need for additional gene identification efforts for AMC. Furthermore, the prominent influence of environmental factors specific to AMC provides a promising area for the identification of prevention targets. We did not observe significant sex differences in the etiology of AMC, although follow-up is warranted in other well-powered studies.