Trends in mass shootings in the United States (2013-2021): A worsening American epidemic of death

Background: Mass shootings represent a significant problem in the United States (US). This study aimed to examine trends in mass shootings in the US over time. Methods: Retrospective mass shooting data (1/2013-12/2021) were collected from the Gun Violence Archive. A scatterplot was constructed showing predicted (extrapolated from 2013 to 2019) versus actual total mass shootings in 2020 and 2021. Multivariate linear regressions were performed to evaluate trends in mass shootings over time, associated with gun law strength. Results: Mass shooting incidents, injuries, and deaths in 2020 and 2021 exceeded extrapolations from previous years. When comparing 2019 to 2020, stronger gun laws were associated with decreased monthly mass shooting deaths. For these same strong gun law states, monthly mass shooting deaths decreased when comparing 2019 to 2021 and comparing 2020 to 2021. Conclusions: US mass shootings have increased over the past decade. Stronger gun laws appear associated with fewer monthly mass shooting-related deaths. Firearm-related legislation may at least partially, curtail the worsening of this substantial "American problem" of mass shootings.