Importance: Firearms are the leading cause of death in US children and adolescents, but little is known about whether the overall legal landscape was associated with excess mortality after a landmark US Supreme Court decision in 2010.
Objective: To measure excess mortality due to firearms among US children aged 0 to 17 years after the McDonald v Chicago US Supreme Court decision (2010).
Design, setting, and participants: An excess mortality analysis was conducted using the US Centers for Disease Control and Prevention's Wide-Ranging Online Data for Epidemiologic Research (WONDER) database before and after McDonald v Chicago, the landmark 2010 US Supreme Court decision on firearms regulation. States were divided into 3 groups based on legal actions taken before and since 2010, most permissive, permissive, and strict. Firearm mortality trends before (1999-2010) and after (2011-2023) were determined and compared across the 3 groups for all intents and by intent (homicide and suicide). Subgroup analysis by observed race and ethnicity was conducted. For each US state, pre-and post-McDonald v Chicago all-intent pediatric firearm mortality incident rates were compared. These data were analyzed January 2011 through December 2023.
Exposure: The pre- and post-McDonald v Chicago legal landscape.
Main outcomes and measures: Excess mortality during the post-McDonald v Chicago period.
Results: During the post-McDonald v Chicago period (2011-2023), there were 6029 excess firearm deaths (incidence rate [IR], 158.6 per million population; 95% CI, 154.8-162.5) in the most permissive group. In the permissive group, there were 1424 excess firearm deaths (IR, 107.5 per million person-years; 95% CI, 103.8-111.3). In the strict group, there were -55 excess firearm deaths (IR, -2.5 per million person-years; 95% CI, -5.8 to 0.8). Non-Hispanic Black populations were had the largest increase in firearm mortality in the most permissive and permissive state groupings. Four states (California, Maryland, New York, and Rhode Island) had decreased pediatric firearm mortality after McDonald v Chicago, all of which were in the strict firearms law group.
Conclusion: States in the most permissive and permissive firearm law categories experienced greater pediatric firearm mortality during the post-McDonald v Chicago era. Future work should focus on determining which types of laws conferred the most harm and which offered the most protection.