Background: Suicide is a leading cause of death for young people. Half of young adult suicides are by firearm, and many involve alcohol consumption. We aimed to assess the impact of the minimum legal drinking age (MLDA) of 21 years on rates of alcohol positive firearm and non-firearm suicide.

Methods: We used a regression discontinuity approach with data from the National Violent Death Reporting System (NVDRS) 2005-2021, among U.S suicide decedents in 14 states aged 16-35 years. The primary outcomes were the change in the proportion of tests positive for alcohol and the change in rates of alcohol positive suicide per 100,000 population at the MLDA.

Findings: Across 14 states and 169 state-years, there were 434 alcohol positive suicides at age 20 and 684 alcohol positive suicides at age 21. The percentage of suicides with a positive alcohol test increased from 29.5% at age 20 to 38.7% at age 21 (p < 0.001), with a larger increase among firearm suicides relative to non-firearm suicides. Accounting for age-related trends, the total alcohol positive suicide rate increased by 1.52 per 100,000 (p < 0.001) at the MLDA, mostly due to an increase in alcohol positive firearm suicide. Compared to the expected rate in the absence of the MLDA, there was a 47.5% (95% CI 24.1%-81.8%) excess in firearm suicides, equivalent to 137 (95% CI 82-191) excess deaths. There was no discontinuity in the rate of alcohol negative firearm suicides at age 21. Blood alcohol content was not affected by the MLDA but was higher for firearm suicides across all ages.

Interpretation: There was a large increase in the rate of alcohol positive suicide at the minimum legal drinking age (MLDA), driven by firearm suicide. Policies and programmes should aim to weaken the link between alcohol and firearms among those at or just above legal drinking age to prevent suicide.

Funding: The Commonwealth Fund and The Joyce Foundation.

Keywords: Alcohol; Firearms; Health policy; Mental health; Suicide.

© 2024 The Authors.