Healthy Sisters of women with eating disorders show a higher level of depressive symptoms than women whose sister is not suffering from an eating disorder, according to a new study. The study also found that the relationship between the sisters, one of whom has an eating disorder, is worse than that between sisters neither of whom suffers from an eating disorder. “The worse the relationship between the two sisters, the greater the level of psychological distress becomes for the healthy one, which in turn places her at risk of developing an eating disorder of her own,” said Prof. Yael Letzer from the Faculty of Social Welfare and Health Sciences.

 In recent decades there has been a significant increase in the incidence of eating disorders, the most prominent of which are anorexia nervosa, bulimia nervosa and binge eating disorder (BED). According to Professor Letzer, these are particularly common among young women and involve multiple psychiatric and physical comorbidities and high mortality rates. Many studies have shown that sibling relations constitute the most continuous relationship of human life, and are considered to be the most significant after that of parent-child.

 In this study, which was conducted by Prof. Letzer along with Prof. Ruth Katz, both from the Faculty of Social Welfare and Health Sciences, and Keren Berger as part of the latter’s master’s thesis in social work, 60 girls and young women aged 13–31 participated, 30 of whom have a sister suffering from an eating disorder: 10 with anorexia nervosa, 10 with bulimia nervosa, and 10 with an unspecified eating disorder. All the subjects were the sisters closest in age to the sister with the eating disorder, their age difference did not exceed 10 years, and the two sisters had lived together at least five years before the study.

The results of the study revealed that, among girls and young women who have sisters with an eating disorder, there is a higher level of negative sibling relations. “In light of the sick sister’s disease, a rivalry develops between the two sisters for the attention of their parents, one which is characterized mostly by ambivalence, frustration, conflict, and frequent transitions between feelings of love and hate. In addition, the healthy sister must take part in the daily treatment of her sister, something which is liable to become a burden for her in her daily life and thereby lead to feelings of frustration, anger, hatred, and fear,” said Prof. Letzer.

The study also found that the sisters of girls or young women suffering from an eating disorder have a higher level of depressive symptoms than sisters of healthy female siblings. According to the researchers, it is possible that the strained relationship between the sisters negatively impacts the healthy sister's mental health.

“In general, a negative relationship between sisters is detrimental to the mental health of the healthy sister, but particularly so when this negative relationship is between a healthy sister and one suffering from an eating disorder; this even places the healthy sister at risk of falling ill as well. Therefore, during treatment maximum attention should be given to the relationship between the two sisters, strengthening it and transforming it from a negative, competitive factor to one of support. In addition, it is extremely important to provide the healthy sister with information about the specific eating disorder and to involve her as much as possible in her sister’s condition in order to facilitate her own coping with the disease,” concluded Prof. Letzer.