Bulimic Behaviors and Early Substance Use: Findings from a Cotwin-Control Study

Background: Bulimic behaviors (i.e., binge eating and compensatory behaviors) and substance use frequently co-occur. However, the etiology underlying this association is poorly understood. This study evaluated the association between bulimic behaviors and early substance use, controlling for genetic and shared environmental factors. Methods: Participants were 3,540 young adult women from the Missouri Adolescent Female Twin Study. A telephone adaptation of the Semi-Structured Assessment for the Genetics of Alcoholism interview assessed DSM-IV bulimic behaviors, substance use, and other psychological characteristics. Lifetime bulimic behaviors were examined in twin pairs concordant and discordant for early substance use. Logistic regressions were adjusted for the nonindependence of twin data, zygosity, age, body mass index, early menarche (onset before age 12), and early sex (first consensual sexual intercourse before age 15). Results: In the entire study population, women who reported early use of alcohol or nicotine were more likely to engage in bulimic behaviors after adjusting for covariates. In 53 pairs of monozygotic twins discordant for alcohol experimentation before age 15, the twin who reported early alcohol experimentation had 3.21 (95% confidence interval = 1.54 to 6.67) times higher odds of reporting bulimic behaviors than the cotwin who did not report early alcohol experimentation, even after adjustment for covariates. Conclusions: Findings suggest that early alcohol experimentation may contribute to the development of bulimic behaviors via mechanisms extending beyond shared vulnerability, including individual-specific environmental experiences or causal pathways.