State gun laws, gun ownership, and mass shootings in the US: cross sectional time seriesBMJ 2019; 364 doi: https://doi.org/10.1136/bmj.l542 (Published 06 March 2019) Cite this as: BMJ 2019;364:l542
- Paul M Reeping, doctoral student1,
- Magdalena Cerdá, associate professor2,
- Bindu Kalesan, assistant professor3,
- Douglas J Wiebe, professor4,
- Sandro Galea, dean5,
- Charles C Branas, professor1
- 1Department of Epidemiology, Columbia University, Mailman School of Public Health, 722 West 168th Street, New York, NY 10032, USA
- 2Department of Population Health, New York University, Langone School of Medicine, New York, NY, USA
- 3Department of Community Health Sciences, Boston University School of Public Health, Boston, MA, USA
- 4Department of Biostatistics, Epidemiology & Informatics, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA, USA
- 5Boston University School of Public Health, Boston, MA, USA
- Correspondence to: P Reeping @PaulReeping on Twitter) (or
- Accepted 28 January 2019
Objective To determine whether restrictiveness-permissiveness of state gun laws or gun ownership are associated with mass shootings in the US.
Design Cross sectional time series.
Setting and population US gun owners from 1998-2015.
Exposure An annual rating between 0 (completely restrictive) and 100 (completely permissive) for the gun laws of all 50 states taken from a reference guide for gun owners traveling between states from 1998 to 2015. Gun ownership was estimated annually as the percentage of suicides committed with firearms in each state.
Main outcome measure Mass shootings were defined as independent events in which four or more people were killed by a firearm. Data from the Federal Bureau of Investigation’s Uniform Crime Reporting System from 1998-2015 were used to calculate annual rates of mass shootings in each state. Mass shooting events and rates were further separated into those where the victims were immediate family members or partners (domestic) and those where the victims had other relationships with the perpetrator (non-domestic).
Results Fully adjusted regression analyses showed that a 10 unit increase in state gun law permissiveness was associated with a significant 11.5% (95% confidence interval 4.2% to 19.3%, P=0.002) higher rate of mass shootings. A 10% increase in state gun ownership was associated with a significant 35.1% (12.7% to 62.7%, P=0.001) higher rate of mass shootings. Partially adjusted regression analyses produced similar results, as did analyses restricted to domestic and non-domestic mass shootings.
Conclusions States with more permissive gun laws and greater gun ownership had higher rates of mass shootings, and a growing divide appears to be emerging between restrictive and permissive states.
Contributors: All authors participated in the writing, editing, creation, and approval of this paper. PMR assembled the data, conducted the analyses, and wrote and edited the original manuscript. CCB first conceptualized the paper and participated in data preparation, analysis, writing, and editing. All authors had full access to the data in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. PMR is the guarantor. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting these criteria have been omitted.
Funding: No extramural funding.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organization for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Owing to the aggregated nature of the count data used in the study, the Institutional Review Board at Columbia University determined that the study was exempt.
Patient consent: Not applicable.
Data sharing: Statistical code and dataset available from the corresponding author.
The lead author (PMR) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained.
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