A Polygenic Score for Body Mass Index is Associated with Depressive Symptoms via Early Life Stress: Evidence for Gene-Environment Correlation

BackgroundIncreasing childhood overweight and obesity rates are associated with not only adverse physical, but also mental health outcomes, including depression. These negative outcomes may be caused and/or exacerbated by the bullying and shaming overweight individuals experience. As body mass index (BMI) can be highly heritable, we hypothesized that a genetic risk toward higher BMI, will predict higher early life stress (ELS), which in turn will predict higher depressive symptoms in adulthood. Such a process will reflect an evocative gene-environment correlation (rGE) wherein an individuals genetically influenced phenotype evokes a reaction from the environment that subsequently shapes the individuals health. MethodsWe modeled genetic risk using a polygenic score of BMI derived from a recent large GWAS meta-analysis. Self-reports were used for the assessment of ELS and depressive symptoms in adulthood. The discovery sample consisted of 524 non-Hispanic Caucasian university students from the Duke Neurogenetics Study (DNS; 278 women, mean age 19.78{+/-}1.23 years) and the independent replication sample consisted of 5 930 white British individuals from the UK biobank (UKB; 3 128 women, mean age 62.66{+/-}7.38 years). ResultsA significant mediation effect was found in the DNS (indirect effect=.207, bootstrapped SE=.10, 95% CI: .014 to .421), and then replicated in the UKB (indirect effect=.04, bootstrapped SE=.01, 95% CI: .018 to .066). Higher BMI polygenic scores were associated with higher depressive symptoms through the experience of higher ELS. ConclusionsOur findings suggest that evocative rGE may contribute to weight-related mental health problems and stress the need for interventions that aim to reduce weight bias, specifically during childhood.