Job market paper
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 and mental illness, but whether mental 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 to Adult Health. To tackle unobservable confounders and reverse causality, I exploit variations in friend and family suicide attempts and a genetic score for depression as instrumental variables. I find that one standard deviation increase in depression symptoms leads to an increase in individuals' engagement in risky health behaviors, including a 16% higher probability of having multiple partners and a 16% higher probability of smoking. These magnitudes are as big as the effect of obtaining a college degree on preventing risky health behaviors. I further show these estimates are robust to individuals fixed unobservables and sizable violation of exclusion restriction assumption. I find that depression could promote individuals' risky health behaviors through altering their risk preferences, contentiousness, future orientation, and perceived social support.