US States with poor social health outcomes and more firearms have more morbidity due to mass shootings.

Background: Mass shootings represent a persistent public health crisis. Prior studies have linked social determinants of health (SDOH) to the phenomenon of gun violence, but there remain limited analyses on mass shooting events specifically.

Methods: Mass shooting events from 2014-2019 were recorded from the Gun Violence Archive. State-level data regarding population, ATF registered weapons, federal firearm licensees and several SDOHs (poverty, unemployment and educational attainment) were collected from publicly-available US governmental databases. Giffords Law Center rankings were used to assess the relative strictness of each state's gun laws. Gun ownership rates were obtained from the RAND Corporation. Bivariate analyses compared each SDOH, as well as ATF registered weapons, Giffords Center ranking and gun ownership rates, to the death rate, injury rate, and combined injury/death rate from mass shootings in each state. All associations were evaluated via Pearson's Rho. Slope and p-values were analyzed, with a threshold significance value of p less than 0.05.

Results: Unadjusted analysis revealed poor mental health, decreased educational attainment and increased unemployment to all be associated with an increased risk of mass shooting-related injury or death. Adjusted analysis revealed fewer firearm regulations, higher gun ownership, lack of handgun magazine restrictions and lack of long-gun registration requirements were associated with an increased risk of mass-shooting death. Similarly, adjusted analysis revealed lack of handgun permit requirements to be associated with both an increased risk of mass shooting-related injury and combined risk of injury/death.

Conclusions: This study revealed associations between multiple SDOH and firearm restrictions with morbidity due to mass shooting events.