Anorexia nervosa and bulimia nervosa: sibling sex ratio and birth rank--a catchment area study.

Abstract

These were to determine (1) whether there is a birth rank effect in eating disorders, and (2) whether all-female sibships are overrepresented in the families of those with eating disorders. The study sample consisted of 293 female patients referred from a defined catchment area, the County of Leicester, United Kingdom, to an eating disorders clinic. Diagnoses were made using DSM-III and DSM-III-R. To discern birth rank effect, this core sample was expanded to one of 673 by adding published data sets to our own. No evidence for either effect was found. Biases which may have obscured genuine effects are discussed. A comment is made on the implication for family theories of causation of these negative findings.