Age 21 handgun purchase policies & adolescent suicide fatalities

Tuesday, June 25, 2019: 1:30 PM
Jefferson - Mezzanine Level (Marriott Wardman Park Hotel)

Presenter: Julia Raifman

Co-Authors: Elysia Larson; Michael Siegel; Michael Ulrich; Colleen Barry; Anita Knopov; Sandro Galea

Discussant: Timothy Classen

Suicide is the second leading cause of death among adolescents aged 15 to 24. At a time of increased recognition of the role of firearms in adolescent fatalities, three states increased the age of handgun purchase to 21 years in 2018. We aimed to evaluate whether changes in state policies limiting handgun sales to those over 21 years, relative to 18 years, were linked to a reduction in adolescent suicide fatalities.
We used suicide mortality data from the Center for Disease Control and Prevention’s Web-based Injury Statistics Query and Reporting System. Among adolescents aged 18 to 20 years, we compared changes in suicide fatality rates in the five years before and after policy changes in three states that changed the age of handgun sales policies relative to changes in suicide fatalities over time in six states with consistent age 18 sales policies. Missouri and South Carolina changed the age of handgun purchase from 21 to 18 years in 2007 and 2008, respectively. West Virginia changed the age of handgun purchase from 18 to 21 years in 2010. We selected Texas and Alabama, Florida and Kentucky, and North Carolina and Indiana as geographically proximate comparison states matched on baseline trends in suicide fatalities for Missouri, South Carolina, and West Virginia, respectively. We used a linear difference-in-differences approach to estimate the relationship between policy changes and all-cause and cause-specific suicide fatality rates, adjusting for state, year, proportion of adult suicides due to firearms, and state poverty and unemployment levels, clustering standard errors by state. As a falsification test, we repeated the main analysis among those aged 13 to 17 years, whom we would not have expected to be affected by the policy change. Due to the small number of states in the sample, we conducted permutation analyses to precisely estimate p-values.
Matched state pairs had parallel trends in suicide fatalities prior to policy changes. Age 21 handgun sales policies were associated with 3.45 fewer suicide fatalities per 100,000 person-years (95% confidence interval [CI]: -3.89 to -3.01, permutation adjusted p-value <0.001) among adolescents aged 18 to 20 years old. They were associated with reduced firearm suicide fatalities (-2.13, 95% CI: -2.84 to -1.41) and with non-firearm suicide fatalities (-1.32, 95% CI: -1.84 to - 0.80). Age 21 handgun policies were not associated with suicide fatalities among those aged 13 to 17 years (0.22, 95% CI: -1.17 to 1.61), satisfying this falsification test. The 28% (95% CI: 24% to 31%) reduction relative to the overall suicide fatality rate of 12.40 suicides per 100,000 person-years would be equivalent to 322 (95% CI: 282 to 363) fewer suicide fatalities among adolescents aged 18-20 years old each year in the 35 US states without age 21 handgun sales policies.
Age 21 handgun sales state policies were associated with reduced adolescent suicide fatalities. Given this evidence and that there is widespread public support for increasing the age of handgun purchase policies, state and national policymakers may wish to consider age 21 handgun purchase policies.