Potential Determinants of Mass Shooting Perpetration and Casualties: A Systematic Review

Introduction: In the United States (US), mass shootings could be regarded as a public health issue due to their ubiquitous and public nature. Social-ecological models, commonly used to explain health behaviours, can contribute to the understanding of potential determinants of mass shootings based on current evidence. Aim: To conduct a systematic review on factors associated with the perpetration of mass shooting events and casualties (injuries or fatalities) at mass shooting events. Materials and Methods: The author searched the literature on PubMed using the term “mass shooting”. Inclusion criteria included titles containing the words “shoot*,” “firearm*,” or “gun*,” having an abstract or full text, and the study being either primary research or secondary data analysis on the perpetration or casualties of mass shootings. Results: The author reviewed 36 articles, nearly all of which focused on mass shootings in US. For the perpetration of mass shootings, gun ownership and access were present at all levels of the social-ecological model. Other factors for perpetration included mental illness, relationship issues, and permissive firearm laws. Mass shooting casualties were associated with the use of high-powered firearms at the intrapersonal level and permissive firearm laws at the policy level. Conclusion: Firearms-related factors were associated with both the perpetration and casualties of mass shootings at various levels of the social-ecological model. However, caveats, including a limited time frame of the review, limited sources of publications, and subjectivity in building the social-ecological model, should be considered in the interpretation of the study findings.