Each 10% increase in refundable state-earned income tax credit (EITC) generosity was associated with a 4.3% relative reduction in firearm suicide rates, according to the results of a recent study.

The cohort study, published in JAMA Network Open, examined whether refundable state-earned income tax credit (EITC) was associated with firearm suicide rates across the United States. Using state-level data from 46 states and Washington, DC, from 1981 through 2019, researchers applied heterogeneity-robust, two-stage difference-in-difference methods to estimate the impact of EITC policies. 

EITC generosity was quantified as the percentage of the federal EITC offered by each state per year, with only refundable credits considered as exposure. Analyses were adjusted for a range of time-varying state-level covariates, including economic indicators and demographic characteristics.

During the study period, 20 states implemented a refundable EITC, with generosity ranging from 3.4% to 85% of the federal credit. In 2019, the national firearm suicide rate was 7.29 per 100,000 persons. Each 10% increase in refundable EITC generosity was associated with a reduction of 0.28 firearm suicide cases per 100,000 person-years, corresponding to a 4.3% relative decline.

Comparing pre- and post-implementation periods, states with refundable EITCs experienced an average reduction of 0.49 firearm suicides per 100,000 person-years, a 7.9% relative decline compared with states without such policies. These associations were identified using the difference-in-difference method but not confirmed in two-way fixed effect models, likely due to known limitations in that approach when treatment effects vary over time.

Event study analyses supported the assumption of parallel trends in the years preceding EITC implementation. “While previous research indicates that poverty-alleviation programs reduce suicide rates, our study shows that they could do so specifically for firearm suicide,” the authors noted, suggesting that reduced economic stress may be a contributing mechanism.

Individual-level causality could not be determined, and residual confounding may remain. Nonetheless, the findings support the potential for economic policies to address upstream determinants of firearm-related mortality.

No conflicts of interest were disclosed in the study.