Firearm legislation: The association between neighboring states and crude death rates.

BACKGROUND:Few studies have examined the impact of interstate differences in firearm laws on state-level firearm mortality. We aim to study the association between neighboring states' firearm legislation and firearm-related crude death rate (CDR). METHODS:The CDC Web-based Injury Statistics Query and Reporting System was queried for adult all-intent (accidental, suicide, and homicide) firearm-related CDR among the 50 states from 2012 to 2020. States were divided into five cohorts based on the Giffords Law Center Annual Gun Law Scorecard, and two groups were constructed: Strict (A, B, C) and Lenient (D, F). We examined the effect of (1) a single incongruent neighbor, defined as "Different" if the state is bordered by ≥1 state with a grade score difference >1, and (2) the average grade of all neighboring states, defined as "Different" if the average of all neighboring states resulted in a grade score difference >1. RESULTS:Strict states with similar average neighbors had significantly lower CDR compared with Strict states with different average neighbors (2.98 [1.91-5.06] vs. 3.87 [2.37-5.94], p = 0.02), while Lenient states with similar average neighbors had significantly higher CDR compared with Lenient states with different average neighbors (6.02 [4.56-8.11] vs. 4.7 [3.95-5.35], p = 0.002). Lenient states surrounded by all similar Lenient states had the highest CDR, which was significantly higher than Lenient states with ≥1 different neighbor (6.52 [5.09-8.96] vs. 5.19 [3.85-6.61], p < 0.001). However, Strict states with ≥1 different neighbor did not have higher CDR compared with Strict states surrounded by all similar Strict states (3.39 [2.17-5.35] vs. 3.14 [1.91-5.38], p = 0.5). CONCLUSION:We report a lopsided neighboring effect whereby Lenient states may benefit from at least one Strict neighbor, while Strict states may be adversely affected only when surrounded by mostly Lenient neighbors. These findings may assist policymakers regarding the efficacy of their own state's legislation in the context of incongruent neighboring states. LEVEL OF EVIDENCE:Prognostic and Epidemiological; Level IV.