Bulimia nervosa: family size, sibling sex and birth order. A catchment-area study.

Family size, sex of siblings and birth order were examined in 225 bulimic patients of normal weight, all stemming from the same circumscribed catchment area. Although bulimia can occur in any size family, all-female sibships were significantly over-represented. In small families at least, the bulimic patient was highly likely to be the only or eldest daughter. In small sibships, a bulimic who was first-born was significantly more likely to have a younger sister; if second-born she was more likely to have an elder brother. Despite the very large sample size, no final conclusion can be made on birth order.