Bulimic symptoms in the Virginia twin study of adolescent behavioral development: Correlates, comorbidity, and genetics

Background: This paper addresses bulimia symptoms in a large community sample of twins aged 8 to 17 years. We aim to identify environmental correlates of bulimia symptoms and relationships with other psychiatric disorder symptoms. The twin design allows examination of the structure of genetic and environmental effects. Methods: DSM-IIIR bulimia symptoms and consequential impairment were measured by interview in the first wave of the Virginia Twin Study of Adolescent Behavioral Development. Comorbidity with other psychiatric symptoms and environmental correlates were examined and the relative contributions of genes and environment were assessed using structural equation modeling. Results: An item-response theory model indicated that the range of bulimic symptoms represented a single underlying trait. Bulimia symptoms were more common in post-menarche girls and positively associated with body-mass index. Subdiagnostic symptomatology was associated with impairment in psychosocial functioning. Bulimia symptoms were strongly associated with other psychiatric disorders symptoms including anxiety and depression. Genetic model fitting identified strong additive genetic effects on the symptom score. Accounting for a potential violation of the equal environment assumption for identical and fraternal twins slightly reduced estimated genetic variance. Conclusions: The pattern of comorbidity suggests overlap between bulimia symptoms and those of internalizing disorders. Substantial genetic variance (44%) was evident in the most conservative model. Biol Psychiatry 2002;51: 172-182 (C) 2002 Society of Biological Psychiatry.