Exploring the complexity of firearm homicides in Harris County, Texas, from 2009 to 2021: Implications for theory and prevention.

Firearm violence is a major health problem in the United States that clusters asymmetrically across geographic and demographic lines, and the persistence and unequal distribution of firearm violence suggests that novel causal explanations and theoretical frameworks may be warranted to guide preventive strategies. Thus, this study explores the following three hypotheses that are grounded in complex systems theory: 1) trends in firearm homicides risks have shifted heterogeneously in Harris County across endemic degree of risk; 2) firearm homicides clusters have remained resilient in Harris County across the study time period; and 3), the associations between known contextual correlates of firearm homicides and the distribution of firearm homicides risks in Harris County have manifested as nonlinear. Using a retrospective study design (n = 4,397) from January 1, 2009-June 31, 2021, medicolegal death investigation data from the Harris County Institute of Forensic Sciences and estimates of community characteristics from the American Community Survey were analyzed using Joinpoint trend analysis, kernel density geospatial analysis, and proportion tests. Trend analyses revealed that firearm homicides risks shifted heterogeneously across endemic degree of risk, with geographical areas with lower initial firearm homicides risks experiencing more profound upward shifts across the time period of the study. Geospatial analyses identified the resiliency of firearm homicides clusters across the study period, particularly in central, southern, and south-western districts of the city. Finally, the relationships between known contextual correlates and the distribution of firearm homicides risks in Harris County appeared to be nonlinear, particularly regarding ethnicity. This study provides data-driven results that suggest the plausibility of complex systems theory in advancing the understanding of causality in firearm homicides. Further, these findings support the urgent need for complex systems-informed preventive efforts that account for spatiotemporal heterogeneity, key interactions that generate nonlinearity, and latent feedback loops that underlie resiliency in firearm homicides.