This dissertation is comprised of three essays, each examining a different topic in health economics. In Chapter 1, I investigate ex ante moral hazard from health insurance, or the effect of insurance on risky behaviors. Specifically, I examine risky sex, a behavior with quick, meaningful consequences. I exploit the requirement insurance cover prescription contraception without cost-sharing. Since this policy affects a small aspect of insurance, I isolate the effect on behavior. Using pre-policy insured rates as a measure of treatment intensity, I find insurance decreases prevention (condom sales) and increases sexually transmitted infections (STIs). To determine insurance’s overall effect, I exploit the requirement insurance cover young adult children. I find the protective effect of insurance on STIs more than compensates for the reduction in prevention. In Chapter 2, I test whether weight impacts mental health. Both average body mass index (BMI) and rates of depression increased over the past several decades; however, scant research has investigated if the correlation between weight and depression reflects a causal effect. Using genetic variation in obesity predisposition as an instrument, I determine the impact of BMI on suicidality and depression. I find BMI impacts suicidal ideation but not other measures of mental health. This effect on suicidal ideation is concentrated in white women. One mechanism through which weight affects mental health is social stigma. In Chapter 3, I investigate the effect of financial aid on health, specifically BMI and general self-report health. Aid lowers the cost of college, which increases college-going. However, there is little evidence on the long-run impact of aid on health. I exploit a 1981 shock in Social Security benefits to test the effect of aid on health. Minor children of retired or disabled Social Security beneficiaries and children with deceased parents are eligible for their own benefits, and before 1981 these children could receiving benefits conditional on college enrollment. Using difference-in-differences, I show benefits for college students reduced women’s BMI and improved general health, but had no effect on men. I also find that aid improved educational attainment for beneficiaries, which is a plausible mechanism between aid and health.