Obesity, Mental Health, Depression, Polygenetic Scores
Eunice Kennedy Shriver National Institute of Child Health and Human Development
The authors thank research assistance from Giuseppe Germinario. This research uses data from Add Health, a program project directed by Kathleen Mullan Harris and designed by J. Richard Udry, Peter S. Bearman, and Kathleen Mullan Harris at the University of North Carolina at Chapel Hill, and funded by grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Special acknowledgment is due to Ronald R. Rindfuss and Barbara Entwisle for assistance in the original design. Information on how to obtain the Add Health data files is available on the Add Health website (http://www.cpc.unc.edu/addhealth). No direct support was received from grant P01- HD31921 for this analysis. The Health and Retirement Study (HRS accession number 0925-0670) is sponsored by the National Institute on Aging (grant numbers NIA U01AG009740, RC2AG036495, and RC4AG039029) and is conducted by the University of Michigan. Additional funding support for genotyping and analysis were provided by NIH/NICHD R01 HD060726. The authors acknowledge research funding from NIH grant number 1R01HD094011-01.
Economic Policy | Economics | Public Affairs, Public Policy and Public Administration
We examine the relationship between body mass index (BMI) and mental health for young adults and elderly individuals using data from the National Longitudinal Study of Adolescent Health and the Health & Retirement Study. While ordinary least squares (OLS) estimates show that BMI is significantly associated with worse mental health in both young adulthood and old age, they are likely to be confounded by (i) unobserved factors that affect both BMI and mental health and (ii) reverse causality. To tackle confounding, we take two complementary approaches. First, we use a polygenic score for BMI as an instrumental variable (IV) and adjust for polygenic scores for other factors that may invalidate this IV. The IV estimates indicate that there is no statistically significant relationship between BMI and mental health for young adults, whereas there is a positive and statistically significant relationship for the elderly. Moreover, we show that IV estimates likely have to be interpreted as identifying a weighted average of effects of BMI on mental health mostly for individuals on the upper quantiles of the BMI distribution. Given potential remaining concerns about the validity of the IV, our second approach is to consider it an “imperfect” IV and estimate an upper bound on the average treatment effect for the corresponding population following Nevo & Rosen (2012). The estimated upper bounds reinforce the conclusions from the IV estimates: they show little evidence of a detrimental effect of BMI on mental health for young adults while being consistent with an economically meaningful effect for elderly individuals. Lastly, we explore some of the potential channels through which BMI may affect mental health for the elderly.
Amin, vikesh; Flores, Carlos A.; and Flores-Lagunes, Alfonso, "The Impact of BMI on Mental Health: Further Evidence from Genetic Markers" (2019). Center for Policy Research. 248.
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