Sex differences in the relative influence of marital status and parenthood on alcohol use disorder symptoms: A multilevel discordant twin design.

Marriage and parenthood are associated with alcohol use and use disorder (AUD), although they are confounded such that many studies struggle to identify their unique and/or causal effects. The present study utilized a genetically informed discordant twin design that strengthens the putative causal role of marital and parental status in the presentation of AUD symptoms by using each individual's cotwin as their own control while simultaneously modeling both predictors among men and women. Participants were 980 complete same-sex twin pairs from the Australian Twin Registry (M-age = 31.70 [SD = 2.48]; 71% women). Marital status, parental status, and past year AUD symptoms were assessed via semistructured interview. Three random-intercept generalized linear mixed models were fit in men and women including (a) marital status only, (b) parental status only, and (c) both marital and parental status; demographics, past year pregnancy, age of first drink, age of regular drinking, personality traits, and antisociality were included as covariates. Models tested for quasi-causal and familial effects. The sole-predictor marital status model (Model 1) provided the best fit among men, while the simultaneous-predictor marital and parental status model (Model 3) provided the best fit among women. Sole-predictor models showed familial effects of both predictors among men and quasi-causal and familial effects of both predictors among women; the simultaneous-predictor model revealed familial effects of marital status only among men and quasi-causal effects of parental status only among women. The present study elucidates important sex differences in the presentation of AUD among midlife adults in the context of notable developmental milestones.