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Comprehensive background check policy and firearm background checks in three US states
  1. Alvaro Castillo-Carniglia1,
  2. Rose M C Kagawa1,
  3. Daniel W Webster2,
  4. Jon S Vernick2,
  5. Magdalena Cerdá1,
  6. Garen J Wintemute1
  1. 1Violence Prevention Research Program, Department of Emergency Medicine, University of California Davis School of Medicine, Sacramento, California, USA
  2. 2Center for Gun Policy and Research, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
  1. Correspondence to Dr Garen J Wintemute, Violence Prevention Research Program, Department of Emergency Medicine, School of Medicine, University of California, Davis 2315 Stockton Blvd, Sacramento, CA 95817 USA; gjwintemute{at}


Background Comprehensive background check (CBC) policies are hypothesised to reduce firearm-related violence because they extend background checks to private party firearm sales, but no study has determined whether these policies actually increase background checks, an expected intermediary outcome. We evaluate the association between CBC policies and the rates of firearm background checks in three states that recently implemented these policies: Delaware (July 2013), Colorado (July 2013) and Washington (December 2014).

Methods We used the synthetic control group method to estimate the difference from estimated counterfactual postintervention trends in the monthly rate of background checks per 1 00 000 people for handguns, long guns and both types combined, using data for January 1999 through December 2016. Inference was based on results from permutation tests. We conducted multiple sensitivity analyses to assess the robustness of our results.

Results Background check rates increased in Delaware, by 22%–34% depending on the type of firearm, following enactment of its CBC law. No overall changes were observed in Washington and Colorado. Our results were robust to changes in the comparison group and statistical methods.

Conclusions The enactment of CBC policies was associated with an overall increase in firearm background checks only in Delaware. Data external to the study suggest that Washington experienced a modest, but consistent, increase in background checks for private party sales, and Colorado experienced a similar increase in checks for sales not at gun shows. Non-compliance may explain the lack of an overall increase in background checks in Washington and Colorado.

  • firearms
  • policy
  • violence
  • time series

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  • Contributors AC-C was involved in the design, and led the implementation of the study, including literature review, data analyses and interpretation and manuscript writing; RMCK was involved in developing the analytical strategy, literature review and manuscript writing; DWW, JSV and MC were involved in the design of the study, interpretation of the findings and critical review of the manuscript and GJW was involved in the conceptualisation, design and implementation of the study, including literature review, interpretation of the findings and manuscript writing. All authors read and approved the final version of the manuscript.

  • Funding This study was funded by the Joyce Foundation (grant ID 15-36377) and the Heising-Simons Foundation (grant ID 2016-219). AC-C and RMCK were supported by the Robertson Fellowship in Violence Prevention Research. AC-C was also supported by Becas Chile as part of the National Commission for Scientific and Technological Research (CONICYT).

  • Disclaimer The funders did not participate in the design and conduct of the study; in the collection, analysis and interpretation of the data or in the preparation, review or approval of the manuscript.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.