Twin studies of eating disorders: A review

Objective: Twin methodology has been used to delineate etiological factors in many medical disorders and behavioral traits including eating disorders. Although twin studies are powerful tools, their methodology can be arcane and their implications easily misinterpreted. Method: The goals of this stu dy are to (a) review the theoretical rationale for twin studies; (b) provid e a framework for their interpretation and evaluation; (c) review extant tw in studies bn eating disorders; and (d) explore the implications for unders tanding etiological issues in eating disorders. Discussion: On the basis of this review, it is not possible to draw firm conclusions regarding the pre cise contribution of genetic and environmental factors to anorexia nervosa. Twin studies confirm that bulimia nervosa is familial and reveal significa nt contributions of additive genetic effects and of unique environmental fa ctors in liability to bulimia nervosa. The magnitude of the contribution of shared environment is less clear, but in the studies with the greatest sta tistical power, it appears to be less prominent than additive genetic facto rs. (C) 2000 by John Wiley & Sons, Inc.