The contribution of genetic and environmental influences underlying disordered eating to exposure to weight-conscious peers

Background. Girls with predispositions for disordered eating (DE) may select into weight-conscious peer groups (i.e. peer groups that emphasize body weight/shape). However, factors driving selection into these peer groups remain unknown, as genetic and/or environmental predisposition to DE may lead girls to select weight-conscious peers. To explore what may drive selection, the present study investigated whether genetic or shared environmental influences underlie associations between DE and exposure to weight-conscious peers and whether effects differ by pubertal status. Methods. Participants included 833 female twins (ages 8–15) from the Michigan State University Twin Registry. Bivariate twin models were conducted to explore etiologic overlap between DE and exposure to weight-conscious peers. Separate models were run for pre-early pubertal girls and mid-late pubertal girls given past research demonstrates differences in genetic and environmental contributions underlying eating pathology by pubertal status. Results. During pre-early puberty, shared and non-shared environmental correlations accounted for the overlap between DE and weight-conscious peer group exposure. Furthermore, shared environmental and non-shared environmental influences underlying DE contributed to 33.3% and 20.0% of the individual differences in weight-conscious peer group membership, respectively. In mid-late puberty, the genetic and non-shared environmental correlations accounted for the overlap between DE and weight-conscious peer group exposure. Genetic and non-shared environmental influences underlying DE contributed to 37.5% and 19.4% of the variance in weight-conscious peer group membership, respectively. Conclusions. While selection effects may exist across development, these effects may be driven by variance in DE due to shared environment in pre-early puberty and genes in mid-late puberty.