Mass Shootings in Major U.S. Cities: The Limited Role of Mental Health and Substance Use Treatment Access Compared to Structural Factors

Background Mass shooting events (MSEs) continue to rise in the United States, posing significant public health concerns. The link between accessibility to these treatments and MSEs remains unclear. This study investigates this relationship in major U.S. metropolitan statistical areas (MSAs), accounting for socioeconomic variables. We hypothesized that limited access to mental health and substance use treatment would be associated with increased MSE incidence. Methods This cross-sectional study analyzed data from 2015 to 2019 from the Gun Violence Archive (GVA) and the Opioid Environment Policy Scan for 48 major U.S. MSAs. MSEs were defined as incidents with 4 or more victims by GVA. Access to treatment services was assessed by proximity to the nearest mental health and substance use treatment providers. Linear regression analyses controlled for sociodemographic factors, including segregation index, unemployment, and poverty rates. Results Between 2015 and 2019, 1200 MSEs resulted in 1219 fatalities and 5208 injuries. No significant correlations were found between MSE incidence and distance to mental health (ρ = −0.17, P = 0.249) or substance use treatment providers (ρ = −0.05, P = 0.749). However, segregation index (β = 0.41, P = 0.004) and unemployment rate (β = 0.67, P < 0.01) were significantly associated with MSE incidence in multivariate analyses. Discussion Access to mental health or substance use treatment alone may not significantly impact MSE incidence. Structural factors, particularly segregation and unemployment, may play a more critical role in MSE. Future research should focus on broader social and structural determinants to reduce MSEs. Level of Evidence III.