UC Davis

This dissertation contributes to literatures on health behaviors: substance use and preventive health behaviors. I provide two unique perspectives on the factors that contribute to the formation of health behaviors. The first two chapters investigate the impact of family environments, specifically siblings, through clean causal study designs. The last chapter analyzes an exogenous health-shock in risk perception, which has under-explored in prior studies.

In chapter 1, I examine the impact of sibling gender on substance use during adolescence. I analyze a sample of dizygotic twins, leveraging the exogenous variation in their assigned sex at birth. This design helps me to address some methodological concerns in studying sibling gender effects and provide robust causal estimates. I find that among male adolescents, having a brother increases the probabilities of using cigarettes, alcohol, and marijuana. Regarding potential mechanisms, I find that the results are consistent with the channel of direct sibling influences, but not with the channels of differential parental investment or family structure.

Chapter 2, written with Geoffrey C. Schnorr, uses data on siblings near the minimum drinking age to provide causal estimates of peer effects in alcohol consumption, exploiting the increase in consumption of the older sibling in a regression discontinuity design. Preferred point estimates imply that younger sibling binge drinking \textit{decreases} at the cutoff. These negative reduced form spillover effects are concentrated in subgroups where the first stage discontinuity is largest, among siblings who are likely to spend more time together, and for measures of excessive alcohol consumption. While our results are somewhat imprecise, we argue that these patterns of heterogeneity are consistent with younger siblings learning from the costs of their older siblings' drinking behavior. Our results are directly interpretable as the effect of peer alcohol consumption, whereas most prior work identifies the effect of exposure to the peer. We explain how this distinction matters for policy.

In chapter 3, which is joint work with Sok Chul Hong and Seojung Oh, we investigate whether changes in risk perception play a critical role in improving of preventive behaviors and health outcomes by examining the 2009 H1N1 influenza (or swine flu) pandemic in Korea. We employ a difference-in-differences estimation strategy by comparing the differential effects of the H1N1 outbreak on the confirmed cases of diseases which can be prevented by preventive behaviors (e.g., intestinal infections) and the cases of diseases which cannot (e.g., injuries). Using unique administrative data from South Korea’s National Health Insurance Service (NHIS), we find that the exogenous increase in health risk reduced the incidence of intestinal infections compared to the injuries during the H1N1 influenza outbreak. The reduction was the most substantial among children under five years of age, with a 25.4\% decline in cases of intestinal infections relative to injuries. Our findings are robust across various alternative specifications. We provide suggestive evidence that active adoption of preventive behaviors is one of the channels underlying the unexpected decrease in diarrhea cases. The effects, however, faded away shortly after the end of the pandemic and did not last in the long run.