This paper provides new evidence on the causal effect of education on adult depression. I use data from The National Longitudinal Study of Adolescent to Adult Health and exploit genetic scores for education attainment as an instrument. I find that an additional year of education has a large and significant protective effect on mental health; one extra year of schooling reduces depression symptoms by 0.1 standard deviations and the probability of experiencing major depression by 2%. These effects are robust when relaxing some critical assumptions of the instrumental variables. I also explore the heterogeneous effects of education on mental health and find suggestive evidence that women gain more mental health benefits from an extra year of schooling but LGB individuals gain less. Mechanism results show that education could affect mental health outcomes from better labor market outcomes and health inputs.

Risky health behaviors, including substance use and risky sexual behaviors, are a major source of preventable deaths in the U.S. Many studies show a strong positive correlation between risky health behaviors with mental illness, but whether mental health illness promotes risky health behaviors remains unclear.  In this paper, I estimate the effect of depression on risky health behaviors at different stages of the life course using data from the National Longitudinal Study of Adolescent Health. To tackle unobservable confounders that could correlate with depression and risky health behaviors, and reverse causality that risky health behaviors could also shift one's depression;  I exploit variations in friend and family suicide attempts and a genetic score for depression as instrumental variables. I find one standard deviation increase in depression symptoms increases the engagement of individuals’ risky health behaviors including increasing the probability of having multiple sexual partners by 5% and the probability of smoking by 16%. These magnitudes are as big as the effect of obtaining a college degree on risky health behaviors. I also find a strong persistence of risky health behaviors from adolescence to adulthood. I further show these estimates are robust to individual fixed unobservables and relaxation of exclusion restriction assumption. 

Social media is viewed to be a key contributor to worsening mental health in adolescents, as most recently reflected in a public health advisory by the US Surgeon General. We provide new evidence on the causal effects of social media on mental health of college students during the Covid‐19 pandemic, exploiting unique, longitudinal data collected before the Covid‐19 pandemic began and at two points during the pandemic. We find small insignificant effects of social media 4 months into the pandemic during a period of social distancing, but large statistically significant negative effects 18 months into the pandemic when colleges were mostly back to normal operations. Using rich data on substance use, exercise, sleep, stress, and social support, we find some evidence of substitution away from activities that better support mental health at later stages of the pandemic but not at early stages. We find that the negative effects of social media are mostly concentrated among socially‐isolated stu- dents. Both social support and resilience protect students from the negative effects of social media use. Policy implications include regulating social media while also bolstering social support and resilience as important protective factors.

This paper provides new insight into the role of non-traditional lenders -- peer-to-peer (P2P) lending platforms in the borrowing choices of small businesses during the Covid-19 crisis through the adoption of micro-level data from LendingClub. We found a substantial increase in demand for the loan from P2P lending (the loan amounts and the number of new loans) for small business purposes from P2P lenders after authorities implemented mobility restriction policies at the state level.