Estimating the effect of state-level gun purchasing policy on county-level firearm suicide mortality

Thesis (Master's)--University of Washington, 2016-08

Although gun violence is one of the most widely discussed issues in American politics, research funding freezes have hindered the development of public health strategies for its prevention. A substantial majority (approximately two-thirds) of annual gun deaths in the United States are suicides, but most political efforts to prevent gun violence focus on homicide. In this study, I evaluated the effectiveness of handgun permit-to- purchase (PTP) laws at preventing firearm suicide. PTP requirements mandate that all potential handgun purchasers at certified sellers must present a permit or license issued by the state. I used a county-level Poisson model controlling for several relevant covariates to estimate the relative risk of firearm suicide one through 35 years after the passage of a state-level PTP requirement. I also tested the popular theory that prevented firearm suicides will manifest as suicides by other means by running the same model with non-firearm suicide as the dependent variable. I found that time since PTP passage was significantly associated with lower firearm suicide rates and that the relative risk by year-since-passage exhibited a pattern that was consistent with my theoretical expectations. Counterintuitively, I also found that PTP requirements had a significant protective effect against non-firearm suicide, a result that suggests that my analysis was subject to unaccounted-for confounding. I ran several sensitivity analyses, which were able substantially clarify the effect of PTP requirements on firearm suicide from the theoretically implausible effect on suicide by all other means I had identified. This study contributes relatively robust evidence to the growing body of literature supporting gun control as a means of suicide prevention, but it also underscores the need for the development of more rigorous data sources and methodologies in the field of gun violence prevention research.