The Insignificant Difference: Discordant Incidence of Anorexia Nervosa in Monozygotic Twins

Two instances of anorexia nervosa in one of a pair of monozygotic twins offered the opportunity to evaluate the relative importance of constitutional and psychological factors and to highlight patterns of experience relevant for the psychodynamic understanding of the disorder. Significant characteristics were the patients' smaller birth size, being more difficult to raise and nondominant, and parental overstressing of twinship, uniformity, and similarities. Manifest illness occurred when the leader twin established her independence and separateness. This constellation is strikingly similar to what has been recognized as characteristic for the occurrence of primary anorexia nervosa in general.