Twin studies and the etiology of eating disorders

Objective: To evaluate the major twin studies of eating disorders in order to consider the empirical standing of the suggestion that these disorders, notably bulimia nervosa, are largely genetically determined. Method: Examin ation of the relevant twin studies and the methods used. Results: The findi ngs of the twin studies are inconsistent and difficult to interpret, with e stimates for the heritability of liability to bulimia nervosa ranging from 0% to 83%, and from 0% to 70% for anorexia nervosa. Methodological reasons for this variability include issues of definition of phenotype, diagnostic reliability violation of the equal environments assumption, and small sampl e sizes. Many of these issues also apply to twin studies of other psychiatr ic disorders. Conclusions: The heritability of eating disorders remains unk nown. A broad view on the etiology of eating disorders should be maintained , with a focus on environmental mechanisms and gene-environment interaction s, as well as continuing genetic studies. (C) 1999 by John Wiley & Sons, In c.