Socio-Spatial Patterns of Suicide Mortality in the United States

Suicides cause more than 49,000 deaths per year in the United States, including 55% associated with the use of a firearm. Across states and counties in the US, suicide mortality exhibits substantial geographical and sociodemographic heterogeneity. However, the role of large-scale social networks in shaping this variation remains underexplored. To assess how both the risk of suicide mortality and the effect of firearm restriction policies propagate through inter-county social ties, we integrate data on county-level suicide mortality (2010-2022) and the Facebook Social Connectedness Index (SCI), a continuous measure of the strength of social ties between counties used to derive weighted averages of neighboring counties out-comes. First, using two-way fixed effects regression models with sociodemographic, economic, and spatial controls, we find that a one-standard-deviation increase in the SCI-weighted average suicide mortality rate of connected counties is associated with an increase of 2.78 suicide deaths per 100,000 people in the focal county (95% CI: 1.06-4.50). Second, we examine Extreme Risk Protection Orders (ERPOs), state-level policies that allow temporary restriction of firearm access for individuals at risk of self-harm. Using a similar statistical approach, we show that counties with stronger social ties to counties located in ERPO-implementing states experience reductions in suicide mortality, even without local policy enactment. Specifically, we find that a one-standard-deviation increase in ERPO social exposure is associated with a decrease of 0.214 suicide deaths per 100,000 people in the focal county (95% CI: 0.0866-0.342). Such a protective association persists when adjusting for geographical proximity and including state-by-year fixed effects that capture time-varying state-level factors. In sum, our findings suggest that social networks can facilitate the diffusion of both harmful exposures and protective interventions. This socio-spatial structuring of suicide mortality underscores the need for prevention strategies that incorporate social network topology, alongside more traditional approaches based on geographical targeting.