A Polygenic Score for Body Mass Index is Associated with Depressive Symptoms via Early Life Stress: Evidence for gene-environment correlation

Abstract

Background Increasing 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 individual’s genetically influenced phenotype evokes a reaction from the environment that subsequently shapes the individual’s health. Methods We 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). Results A 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. Conclusions Our 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.