GENETIC EPIDEMIOLOGY OF BINGING AND VOMITING

Background Bulimia nervosa is typically defined as the combination of the behaviours of binging and vomi ting.We sought to clarify the relat ionship of these behaviours from a genetic epidemiological perspective . Method Using data on the lifetime history of binging and vomiting fr om a personally interviewed population-based sample of female twins (n =1897), we applied bivariate twin modelling to estimate the sources of variation for these traits. Results The association between having ev er binged (23.6%) and having ever induced vomiting (4.8%) was very str ong (odds ratio=8.78, P <<0.0001). The best-fitting model indicated th at lifetime binging and vomiting were both heritable (46% and 72%) and influenced by individual -specific environmental factors (54% and 28% ). The overlap between the genetic (r(a)=0.74) and individual-specific environmental factors (r(e)=0.48) for the two traits was substantial. No violations of the equal environment assumption were evident. Concl usions including binging and vomiting under the rubric of bulimia nerv osa appears to be appropriate.Our data are consistent with the identif ication of binging and vomiting as complex traits resulting from the i nterplay of multiple genes and individual-specific environmental influ ences. in contrast to 'environmentalist' theories, our results suggest that genetic influences may be of particular relevance to the aetiolo gy of binging and vomiting.