Research

This paper studies how peers’ genetic predisposition to depression affects own mental health during adolescence and early adulthood using data from the National Longitudinal Study of Adolescent to Adult Health (Add Health). I exploit variation within schools and across grades in same-gender grademates' average polygenic score—a linear index of genetic variants—for major depressive disorder (the MDD score). An increase in peers' genetic risk for depression has immediate negative impacts on own mental health. A one standard deviation increase in same-gender grademates' average MDD score significantly increases the probability of being depressed by 2.3 and 3 percentage points for adolescent girls (an 8.7% increase) and boys (a 20% increase), respectively. The effects persist into adulthood for females, but not males. I explore several potential mechanisms underlying the effects and find that an increase in peers' genetic risk for depression in adolescence worsens friendship, increases substance use, and leads to lower socioeconomic status. These effects are stronger for females than males. Overall, the results suggest there are important social-genetic effects in the context of mental health.

Many health conditions have a strong genetic component. We examine whether genetic factors related to risky health behaviors explain variation in health. Using data from the Health and Retirement study, we estimate associations between health and the genetic endowments linked to smoking initiation and intensity. Among those aged 50-65, higher genetic predisposition for smoking is associated with worse health, even after flexibly controlling for individual smoking behavior and among those who have never smoked, suggesting the genetic endowments correlate with health through non-smoking channels. The genetic endowments for smoking correlate with longevity expectations, planning horizons, and measures of conscientiousness, but these channels do not fully explain the estimated relationship between genetic risk for smoking and health. Furthermore, we find that an increase in a spouse's genetic risk for smoking intensity has adverse spillovers for own health. Overall, our results suggest the genetic factors linked to smoking capture a complex array of traits that correlate with less engagement in health-promoting activities.

Genetic factors play a major role in the development of Alzheimer’s disease and related dementias (ADRD). With increased access to genetic data, observable genetic factors could impact household planning and medical care if they contain actionable information, meaning that they i) are associated with significant harms, ii) reflect risks for which individuals are not already prepared, and iii) are informative above and beyond current knowledge or expectations. We examine these properties for existing genetic measures related to ADRD in the Health and Retirement Study (HRS). We replicate existing relationships between genetic factors and cognitive health. We also show that higher genetic risk is associated with worse economic outcomes on several dimensions including work, income, and wealth. Surprisingly, individuals at higher risk are less likely to engage in planning activities that could mitigate the consequences of cognitive decline (e.g., holding long-term care insurance or assigning durable power of attorney). In predictive exercises, existing genetic indices provide clinically valuable and policy-relevant information on the development of severe adverse cognitive outcomes in the future. Our findings suggest there is a large population of individuals at genetic risk for ADRD who are not protected from cognitive decline despite genetic risk, not insulated from its economic consequences, and relatively unprepared to deal with possible burdens of future ADRD.