GENETIC INFLUENCES ON EATING ATTITUDES IN A NORMAL FEMALE TWIN POPULATION

The Eating Attitudes Test (EAT) and the Eating Disorder Inventory (EDI) were administered to a female volunteer twin population aged 18 to 45 years. Both members of 147 monozygotic (MZ) and 99 dizygotic (DZ) twin pairs completed the questionnaires. Thirty-five subjects scored over the cut-off point of the EAT-26. Interviews of these high-scoring twins and their co-twins identified three subjects with a past history of anorexia nervosa, and three others with a history of a partial syndrome. A heritability value of 41 % was obtained for the overall EAT scores, while factor analysis produced a 'dieting' factor with a heritability of 42 %. The 'body dissatisfaction' and 'drive for thinness' subscales of the EDI had heritability values of 52 and 44 % respectively. The genetic contribution to the variance in body mass index in the twin sample was estimated at 64 %. For all the above phenotypes, an environmental model of transmission with heritability constrained to be zero, could be rejected. Conversely, we were unable to reject a purely additive genetic model with shared environmental variance constrained at zero, suggesting that family environment has little or no effect on the transmission of many of these traits.