Differential environmental factors in anorexia nervosa: A sibling pair study

Objectives. Previous studies have explored differences in psychosocial and familial factors between women who develop anorexia nervosa and those who d o not. However, these studies have generally used between-group comparisons . This study looks at the environmental factors which may be antecedents of anorexia nervosa looking at sister pairs where one had anorexia nervosa an d the other did not. Design. A paired design was used to compare anorexic women with an unaffect ed sister on a number of background variables, including sibling interactio n, parental care, peer group characteristics and other events unique to the individual. Methods. The Sibling Inventory of Differential Experience (SIDE) was used t o determine non-shared environment. Out of an initial sample of 148 women w ith past or current anorexia nervosa, 28 were identified who had sisters wi th no reported history of eating disorders and who also consented to comple te the questionnaire. Results. Anorexic sisters perceived more maternal control and reported more antagonism towards and jealousy of their sisters than did unaffected siste rs. In addition, anorexic women reported having had fewer friends and boyfr iends than their sisters. Conclusions. These results confirm the perceived differences in background environment between women with and women without anorexia nervosa. These is sues are discussed in relation to behavioural genetics, family dynamics and psychosexual development.