A twin study of alcohol dependence, binge eating, and compensatory behaviors.

OBJECTIVE Rates of alcohol dependence are elevated in women with eating disorders who engage in binge eating or compensatory behaviors compared with women with eating disorders who do not report binge eating or compensatory behaviors and with healthy controls. Alcohol dependence, binge eating, and compensatory behaviors are heritable; however, it is unclear whether a shared genetic liability contributes to the phenotypic association among these traits, and little information exists regarding this shared liability in men. We investigated genetic and environmental correlations among alcohol dependence, binge eating, and compensatory behaviors in male and female twins. METHOD Participants included 5,993 same- and opposite-sex twins from the Australian Twin Registry who completed a modified version of the Semi-Structured Assessment for the Genetics of Alcoholism that assessed lifetime alcohol dependence and binge eating as defined in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised. Compensatory behaviors were assessed via a general health questionnaire in women only. Biometrical twin models estimated genetic and environmental influences on alcohol dependence, binge eating, and compensatory behaviors. RESULTS In women, the multivariate twin model suggested that additive genetic and nonshared environmental effects influenced alcohol dependence, binge eating, and compensatory behaviors, with heritability estimates ranging from 38% to 53%. The best-fitting sex-limitation model was a common effects model that equated all genetic and nonshared environmental influences in men and women. The heritability estimates were 50% and 38% for alcohol dependence and binge eating, respectively. Overall, there were significant genetic correlations between alcohol dependence and binge eating, alcohol dependence and compensatory behaviors, and binge eating and compensatory behaviors. CONCLUSIONS These findings indicate that common genetic factors may underlie the vulnerability to alcohol dependence and the liability to binge eating and compensatory behaviors.