No abstract

The Scarr-Rowe hypothesis predicts that the heritability of cognitive abilities is higher in more privileged socioeconomic conditions, meaning that genetic potential can be more fully expressed in environments characterized by high socioeconomic status (SES) compared to low SES. This gene × SES interaction, however, has been replicated mostly in the United States, but not in other Western nations like the United Kingdom. In the current study, we tested the interaction between childhood SES and the heritability of cognitive ability in 3,074 German twin pairs comprising three age cohorts at different developmental stages (mean ages of 11, 17, and 23 years). Higher SES was associated with significantly higher mean cognitive ability scores in the two younger cohorts, with reduced variances at higher SES levels. Results further support the Scarr-Rowe hypothesis in middle childhood, and to some degree in adolescence, but not in adulthood. This indicates that the role of family SES as a moderator of the heritability of cognitive ability changes as children grow older. Moreover, children’s shared experiences appear to be explain more variance in cognitive ability at the lower end of the SES distribution in middle childhood and adolescence.

Emerging evidence suggests socioeconomic disadvantage may increase risk for eating disorders (EDs). However, there are very few studies on the association between disadvantage and EDs, and all have focused on individual-level risk factors (e.g., family income). Neighborhood disadvantage (i.e., elevated poverty and reduced resources in one's neighborhood) is associated with increased risk for anxiety/depression and poor physical health. To date, no studies have examined phenotypic associations between neighborhood disadvantage and disordered eating, or how any form of disadvantage may interact with genetic individual differences in risk for EDs. We examined phenotypic and etiologic associations between neighborhood disadvantage and disordered eating in 2,922 girls ages 8-17 from same-sex twin pairs recruited through the Michigan State University Twin Registry. Parents rated the twins on nine items assessing core disordered eating symptoms (e.g., weight preoccupation, binge eating), and neighborhood disadvantage was calculated from 17 indicators of contextual disadvantage (e.g., median home value, neighborhood unemployment). Puberty was measured using the Pubertal Development Scale to examine whether associations were consistent across development. At a phenotypic level, greater neighborhood disadvantage was associated with significantly greater disordered eating symptoms in girls at all stages of puberty (b = .07). Moreover, Genotype 3 Environment models showed that girls living in more disadvantaged neighborhoods exhibited stronger and earlier (i.e., during pre/ early puberty) activation of genetic influences on disordered eating. Results highlight the critical importance of considering contextual disadvantage in research on etiology and risk for disordered eating, and the need for increased screening and treatment for EDs in disadvantaged youth. General Scientific SummaryThis was the first study to examine the association between neighborhood disadvantage and disordered eating in girls. We found that neighborhood disadvantage was associated with significantly greater disordered eating symptoms across all stages of puberty in girls, and that girls living in disadvantaged neighborhoods exhibited stronger and earlier (i.e., during pre/early puberty) activation of genetic influences on disordered eating. Results indicate that neighborhood disadvantage is a critical contextual factor with implications for etiology and risk for disordered eating in girls.