Do Siblings have a Different Influence on Self-Assessed Family Functioning in Patients with Anorexia and Bulimia Nervosa?

The impact of family factors, particularly the sibling status, on the development and course of eating disorders has been rarely investigated. Therefore, the aim of the present study was to assess a putative association between sibling status and self-rated family dysfunctionality in a large sample of study participants with bulimia nervosa and anorexia nervosa. A total cohort of n = 568 outpatients aged twelve years and older, of whom half had the diagnosis of anorexia (n = 288, 50.7 %), was assessed for self-rated family dysfunctionality using the well-validated German General Family Questionnaire (FB-A), while the symptom level (Global Severity Index) was determined using the SCL-90-Rsymptom checklist. Patients with anorexia were more frequently only children compared to the bulimia group who had generally more siblings (22.6% vs. 14.4%, p = 0.012). In patients with bulimia nervosa, bivariate analyses revealed a significant positive association between the presence of siblings and the degree of family dysfunctionality (only child: 33.6 +/- 17.6, sibling child: 39.3 +/- 15.5, p = 0.043). Linear regression models adjusted for age, body-mass index, parents living in separation, and the Global Severity Index (GSI) confirmed a significant association between higher family dysfunctionality as a dependent variable and sibling status (beta = 0.163, 95% confidence interval [CI] = 1.431; 12.774, p = 0.014). No such relationship was found in the anorexia group (p = 0.418). The differential associations between sibling status and self-rated family dysfunctionality found for the two eating-disorder entities may indicate differences in the pathogenesis of anorexia and bulimia nervosa.