Firearm Laws and Firearm Homicides: A Systematic Review.

Importance: Firearm homicide is a leading cause of injury death in the United States, and there is considerable debate over the effectiveness of firearm policies. An analysis of the effectiveness of firearm laws on firearm homicide is important to understand optimal policies to decrease firearm homicide in the United States. Objective: To evaluate the association between firearm laws and preventing firearm homicides in the United States. Evidence Review: We evaluated peer-reviewed articles from 1970 to 2016 focusing on the association between US firearm laws and firearm homicide. We searched PubMed, CINAHL, Lexis/Nexis, Sociological Abstracts, Academic Search Premier, the Index to Legal Periodicals and Books, and the references from the assembled articles. We divided laws into 5 categories: those that (1) curb gun trafficking, (2) strengthen background checks, (3) improve child safety, (4) ban military-style assault weapons, and (5) restrict firearms in public places and leniency in firearm carrying. The articles were assessed using the standardized Guide to Community Preventive Services data collection instrument and 5 additional quality metrics: (1) appropriate data source(s) and outcome measure(s) were used for the study, (2) the time frame studied was adequate, (3) appropriate statistical tests were used, (4) the analytic results were robust, and (5) the disaggregated results of control variables were consistent with the literature. Findings: In the aggregate, stronger gun policies were associated with decreased rates of firearm homicide, even after adjusting for demographic and sociologic factors. Laws that strengthen background checks and permit-to-purchase seemed to decrease firearm homicide rates. Specific laws directed at firearm trafficking, improving child safety, or the banning of military-style assault weapons were not associated with changes in firearm homicide rates. The evidence for laws restricting guns in public places and leniency in gun carrying was mixed. Conclusions and Relevance: The strength of firearm legislation in general, and laws related to strengthening background checks and permit-to-purchase in particular, is associated with decreased firearm homicide rates. High-quality research is important to further evaluate the effectiveness of these laws. Legislation is just 1 part of a multipronged approach that will be necessary to decrease firearm homicides in the United States.