Worldwide 15-40% of adolescents practice Disordered Eating Behavior (DEB). This study examined DEB development and the role of (1) shared familial factors among sibling pairs; and (2) non-shared familial experiences among discordant sibling pairs adjusted for individual and shared familial factors.

The "National Longitudinal Study of Adolescent Health" data on 3274 adolescents were analyzed. The sample contained: twins (n=952), full siblings (n=1434), half siblings (n=418), and biologically not-related siblings (n=470). Multivariable regression analysis examined familial factors associated with DEB in the overall sample and sibling pair types.

Adolescents engaging in DEB (∼16%) were more likely to be white females with higher BMI and lower self-esteem. Sibling engagement in DEB was associated with: higher quarrel frequency; lack of feeling loved; perceived parental differential attention and restricted independent decision making; lower academic expectations; and reduced paternal closeness. Female-female siblings were 2.5 times (AOR: 2.49, 95% CI. 1.58-3.95) more likely to have DEB compared to male-female pairs. Twin siblings were 48% (AOR: 0.52 95% CI. 0.27-0.98) less likely to engage in DEB compared to biologically not-related siblings. Among discordant sibling pairs, the only observed difference was siblings engaging in DEB reported spending lot more time with the same friend (AOR: 1.92, 95% CI. 1.0-3.6) compared to their non-disordered eating sibling.

This investigation confirms risk factors for DEB and suggests a possible role of the NSFE in discordant patterns of DEB among siblings. In examining the results, one possible conclusion is that NSFE truly does not play a significant role in the development of DEB. Siblings' experience within the family is similar and perhaps there are factors outside the family, such as the relationship with friends that are the stronger influence. Identifying factors associated with DEB may assist school and health care personnel to observe "red flags" related to more serious eating disorders. To adequately explore these issues, future studies must assure sufficient power to detect perceived differences in familial experiences and restrict variables examined to familial factors eliminating peer issues. This study generates questions and hypotheses that warrant further exploration of familial and extra-familial non-shared influences among siblings affected by DEB.