Importance: Laws mandating a minimum age to purchase or possess firearms are viewed as a potentially effective policy tool to reduce homicide by decreasing young adults' access to firearms.
Objective: To evaluate whether state laws that raised the minimum age to purchase and/or possess a handgun to 21 years were associated with lower rates of firearm homicide perpetrated by young adults aged 18 to 20 years.
Design, setting, and participants: In this difference-in-differences analysis of a national cohort, young adult-perpetrated homicide rates were compared between states that did and did not implement stricter minimum age laws than the 1994 federal statute, adjusting for state-level factors. Under 1994 US federal law, the minimum age to purchase a handgun from a licensed dealer is 21 years; to purchase a handgun from an unlicensed dealer, 18 years; and to possess a handgun, 18 years. The 12 states that raised the minimum ages to purchase and/or possess a handgun beyond those set by federal law before 1994 were excluded from the stricter implementation group. Data were collected from January 1, 1995, to December 31, 2017, and analyzed from November 7, 2019, to June 23, 2020.
Exposures: Implementation of state law to raise the minimum age to purchase and/or possess a handgun beyond federal minimum age laws. During the study period, Massachusetts, Maryland, New Jersey, New York, and Wyoming raised the minimum age from 18 to 21 years to purchase a handgun from all dealers. With the exception of Wyoming, these states also increased the minimum age from 18 to 21 years to possess a handgun.
Main outcomes and measures: Firearm homicides perpetrated by young adults aged 18 to 20 years. Homicide data were obtained from the Supplementary Homicide Reports.
Results: During the study period, 35 960 firearm homicides were perpetrated by young adults aged 18 to 20 years. There was no statistically significant change in the rates of homicide perpetrated by this age group in the 5 states that imposed stricter age limits compared with the 32 that did not (crude incidence rate ratio, 1.10; 95% CI, 0.86-1.40). The adjusted incidence rate ratio was 1.14 (95% CI, 0.89-1.45) in states that implemented stricter minimum age laws compared with those that did not.
Conclusions and relevance: This study found that stricter state minimum age laws were not associated with significantly lower rates of young adult-perpetrated homicide in states that adopted them compared with states that did not, and policy makers should reassess their use.