Fletcher, Jason M.
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Publication Mental Health, Schooling Attainment and Polygenic Scores: Are There Significant Gene-Environment Associations?(2020-02-04) Amin, Vikesh; Behrman, Jere R.; Fletcher, Jason M.; Flores, Carlos A.; Flores-Lagunes, Alfonso; Kohler, Hans-PeterWe estimate associations between a polygenic score (PGS) for depressive symptoms, schooling attainment and genetic-environmental (GxE) associations with depressive symptoms and depression for 29 years old in the National Longitudinal Study of Adolescent Health (Add Health) and 53 years old in the Wisconsin Longitudinal Study (WLS). We find some suggestive evidence that the association of the PGS with mental health is lower for more-schooled older individuals in the WLS, but no evidence in Add Health. Quantile regression estimates also show that in the WLS the GxE associations are statistically significant only in the upper parts of the conditional depressive symptoms score distribution. We assess the robustness of the OLS results to possible omitted variable bias by estimating sibling fixed-effect regressions. The sibling fixed-effect results must be qualified, in part due to low statistical power. However, they show that college education is associated with fewer depressive symptoms in both datasets.Publication Does Schooling Improve Cognitive Abilities at Older Ages: Causal Evidence from Nonparametric Bounds(2022-05-19) Amin, Vikesh; Behrman, Jere R.; Fletcher, Jason M.; Flores, Carlos A.; Flores-Lagunes, Alfonso; Kohler, Hans-PeterWe revisit the much-investigated relationship between schooling and health, focusing on cognitive abilities at older ages using the Harmonized Cognition Assessment Protocol in the Health & Retirement Study. To address endogeneity concerns, we employ a nonparametric partial identification approach that provides bounds on the population average treatment effect using a monotone instrumental variable together with relatively weak monotonicity assumptions on treatment selection and response. The bounds indicate potentially large effects of increasing schooling from primary to secondary but are also consistent with small and null effects. We find evidence for a causal effect of increasing schooling from secondary to tertiary on cognition. We also replicate findings from the Health & Retirement Study using another sample of older adults from the Midlife in United States Development Study Cognition Project.Publication Genetic Risks, Adolescent Health and Schooling Attainment(2020-06-25) Amin, Vikesh; Behrman, Jere R.; Fletcher, Jason M.; Flores, Carlos A.; Flores-Lagunes, Alfonso; Kohler, Hans-PeterWe provide new evidence on the effect of adolescent health behaviors/outcomes (obesity, depression, smoking, and attention deficit hyperactivity disorder (ADHD)) on schooling attainment using the National Longitudinal Study of Adolescent to Adult Health. We take two different approaches to deal with omitted variable bias and reverse causality. Our first approach attends to the issue of reverse causality by using health polygenic scores (PGSs) as proxies for actual adolescent health. Second, we estimate the effect of adolescent health using sibling fixed-effects models that control for unmeasured genetic and family factors shared by siblings. We use the PGSs as additional controls in the sibling fixed-effects models to reduce concerns about residual confounding from sibling-specific genetic differences. We find consistent evidence across both approaches that being genetically predisposed to smoking and smoking regularly in adolescence reduces schooling attainment. We find mixed evidence for ADHD. Our estimates suggest that having a high genetic risk for ADHD reduces grades of schooling, but we do not find any statistically significant negative effects of ADHD on grades of schooling. Finally, results from both approaches show no consistent evidence for a detrimental effect of obesity or depression on schooling attainment.Publication Does Schooling Improve Cognitive Abilities at Older Ages(2023-02-02) Amin, Vikesh; Behrman, Jere R.; Fletcher, Jason M.; Flores, Carlos A.; Flores-Lagunes, Alfonso; Kohler, Hans-PeterAn estimated 11% of U.S. adults aged 65 or older have dementia, and as the population ages, dementia cases are predicted to nearly double from 5.2 million in 2019 to 10.2 million by 2050. Understanding how education levels may affect cognitive decline and presumably dementia is important for projecting future dementia in the population and potentially helping individuals understand and possibly reduce their risk. Prior research has suggested a link between more schooling and better later-life performance on cognitive tests. However, most of these studies provided suggestive associations rather than causal estimates. When prior studies did provide causal estimates, inferences were generally based on changes in educational levels after compulsory schooling laws were enacted. This limited estimated causal effects of schooling to the lower grade levels targeted by the laws and the individuals affected by them. In this study, the authors expanded the evidence about causal effects of schooling on older adults to higher levels of schooling, such as attending college, and to a broader population. The authors applied advanced methods to data from a national, longitudinal cohort study representative of U.S. individuals over age 50.