Gun Policy Research Review

The primary focus of our analysis was the systematic review of 18 broad classes of gun policies that have been implemented in some states and the effects of those policies on eight outcomes. We produced research syntheses that describe the quality and findings of the best available scientific evidence. Each synthesis presents and rates the available evidence and describes what conclusions, if any, can be drawn about the policy’s effects on outcomes. In many cases, we were unable to identify any research that met our inclusion criteria (which required a study to provide minimally persuasive evidence for a policy’s effects).

Overall, we found statistically significant evidence that ten of the 18 policies affect four of the main outcomes. For the remaining policies from our analysis, either the policies had inconclusive effects on outcomes or no research about the policies met our inclusion criteria. This does not mean that these policies are ineffective; they might well be quite effective. Instead, it partly reflects shortcomings in the contributions that scientific study can currently offer to policy debates in these areas.

View the research methodology

Strength of Evidence for Relationships Between Gun Policies and Gun Use Outcomes

Here, we show the strength of evidence for relationships between all of the policies and outcomes we examined. Click on any cell with an evidence strength to view a more-detailed analysis.

Policies Regulating Who May Legally Own, Purchase, or Possess Firearms

	Gun Use Outcomes
Gun Policies	Defensive Gun Use	Gun Industry Outcomes	Hunting and Recreation	Mass Shootings	Officer-Involved Shootings	Suicide	Unintentional Injuries and Deaths	Violent Crime
Extreme Risk Protection Orders	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how extreme risk protection orders affect suicide.	No studies met our criteria.	No studies met our criteria.
Minimum Age Requirements	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how minimum age requirements affect mass shootings.	No studies met our criteria.	There is limited evidence that minimum age requirements decrease firearm suicides.	There is inconclusive evidence for how minimum age requirements affect unintentional firearm deaths.	There is inconclusive evidence for how minimum age requirements affect homicides.
Prohibitions Associated with Domestic Violence	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how prohibitions associated with domestic violence affect suicide.	No studies met our criteria.	There is moderate evidence that prohibitions associated with domestic violence decrease intimate partner homicides.
Prohibitions Associated with Mental Illness	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how prohibitions associated with mental illness affect suicide.	No studies met our criteria.	There is limited evidence that prohibitions associated with mental illness decrease violent crime.
Surrender of Firearms by Prohibited Possessors	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how surrender of firearms by prohibited possessors has an effect on violent crime.

Policies Regulating Firearm Sales and Transfers

	Gun Use Outcomes
Gun Policies	Defensive Gun Use	Gun Industry Outcomes	Hunting and Recreation	Mass Shootings	Officer-Involved Shootings	Suicide	Unintentional Injuries and Deaths	Violent Crime
Background Checks	No studies met our criteria.	There is inconclusive evidence for how background checks affect firearm manufacturers or retailers.	No studies met our criteria.	There is inconclusive evidence for how background checks affect mass shootings.	No studies met our criteria	There is inconclusive evidence for how background checks affect suicide.	No studies met our criteria.	There is moderate evidence that background checks decrease firearm homicides.
Bans on Low-Quality Handguns	No studies met our criteria.	There is inconclusive evidence for how bans on low-quality handguns affect firearm purchases.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria	There is inconclusive evidence for how bans on low-quality handguns affect suicide.	No studies met our criteria.	There is inconclusive evidence for how bans on low-quality handguns affect homicides.
Bans on the Sale of Assault Weapons and High-Capacity Magazines	No studies met our criteria.	There is limited evidence that bans on the sale of assault weapons and high-capacity magazines increase the price of banned firearms in the short term.	No studies met our criteria.	There is inconclusive evidence for how bans on the sale of assault weapons and high-capacity magazines affect mass shootings.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how bans on the sale of assault weapons and high-capacity magazines affect homicides.
Firearm Safety Training Requirements	No studies met our criteria.	There is inconclusive evidence for how firearm safety training requirements affect firearm purchases.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	There is inconclusive evidence for how firearm safety training requirements affect homicides.
Firearm Sales Reporting, Recording, and Registration Requirements	No studies met our criteria.	There is inconclusive evidence for how firearm sales reporting, recording, and registration requirements affect firearm purchases .	No studies met our criteria.	There is inconclusive evidence for how firearm sales reporting, recording, and registration requirements affect mass shootings.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.
Licensing and Permitting Requirements	No studies met our criteria.	There is inconclusive evidence for how licensing and permitting requirements affect firearm manufacturers or retailers.	No studies met our criteria.	There is inconclusive evidence for how licensing and permitting requirements affect mass shootings.	No studies met our criteria.	There is limited evidence that licensing and permitting requirements decrease suicide.	No studies met our criteria.	There is inconclusive evidence for how licensing and permitting requirements affect homicides.
Lost or Stolen Firearm Reporting Requirements	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.
Waiting Periods	No studies met our criteria.	There is inconclusive evidence for how waiting periods affect firearm ownership, firearm manufacturers or retailers, or firearm purchases.	No studies met our criteria.	There is inconclusive evidence for how waiting periods affect mass shootings.	No studies met our criteria.	There is moderate evidence that waiting periods decrease firearm suicides.	No studies met our criteria.	There is moderate evidence that waiting periods decrease homicides.

Policies Regulating the Legal Use, Storage, or Carrying of Firearms

	Gun Use Outcomes
Gun Policies	Defensive Gun Use	Gun Industry Outcomes	Hunting and Recreation	Mass Shootings	Officer-Involved Shootings	Suicide	Unintentional Injuries and Deaths	Violent Crime
Child-Access Prevention Laws	No studies met our criteria.	There is inconclusive evidence for how child-access prevention laws affect firearm manufacturers or retailers.	No studies met our criteria.	There is inconclusive evidence for how child-access prevention laws affect mass shootings.	No studies met our criteria.	There is supportive evidence that child-access prevention laws decrease firearm self-injuries among young people.	There is supportive evidence that child-access prevention laws decrease unintentional firearm injuries and deaths among young people.	There is limited evidence that child-access prevention laws decrease assaults.
Concealed-Carry Laws	No studies met our criteria.	There is inconclusive evidence for how concealed-carry laws affect firearm ownership and purchases.	No studies met our criteria.	There is inconclusive evidence for how concealed-carry laws affect mass shootings.	No studies met our criteria.	There is inconclusive evidence for how concealed-carry laws affect suicide.	There is inconclusive evidence for how concealed-carry laws affect unintentional injuries and deaths.	There is limited evidence that concealed-carry laws increase violent crime.
Gun-Free Zones	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.
Laws Allowing Armed Staff in K–12 Schools	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.	No studies met our criteria.
Stand-Your-Ground Laws	There is inconclusive evidence for how stand-your-ground laws affect defensive gun use.	There is inconclusive evidence for how stand-your-ground laws affect firearm ownership and purchases.	No studies met our criteria.	There is inconclusive evidence for how stand-your-ground laws affect mass shootings.	No studies met our criteria.	There is inconclusive evidence for how stand-your-ground laws affect suicide.	No studies met our criteria.	There is supportive evidence that stand-your-ground laws increase firearm homicides.

Strength of Evidence Definitions

No studies: No studies meeting our inclusion criteria evaluated the policy’s effect on the outcome.
Inconclusive: Studies with comparable methodological rigor identified inconsistent evidence for the policy’s effect on an outcome, or a single study found only uncertain or suggestive effects.
Limited: At least one study meeting our inclusion criteria and not otherwise compromised by serious methodological weaknesses reported a significant effect of the policy on the outcome, and no studies with equivalent or stronger methods provided contradictory evidence.
Moderate: Two or more studies⁠—at least one of which was not compromised by serious methodological weaknesses⁠—found significant effects in the same direction, and contradictory evidence was not found in other studies with equivalent or stronger methods.
Supportive: At least three studies not compromised by serious methodological weaknesses found suggestive or significant effects in the same direction using at least two independent data sets.

Note: In some cases, we found evidence for more than one sub-outcome for a given policy, and the strengths of the evidence differed across the sub-outcomes. For example, there is supportive evidence that child-access prevention laws decrease unintentional injuries and deaths among children, while there is limited evidence that these laws decrease the same outcome among adults. In this table, we show the highest strength of evidence for a policy and outcome relationship. To see details of all sub-outcomes, click on the associated box in the table.

Essays on Gun Policy Topics

Law Enforcement Approaches to Reduce Community Gun Violence
Apr 22, 2020
The Relationship Between Firearm Availability and Suicide
Mar 2, 2018
Mass Shootings in the United States
Apr 15, 2021
The Effects of the 1996 National Firearms Agreement in Australia on Suicide, Homicide, and Mass Shootings
Apr 15, 2021
Education Campaigns and Clinical Interventions for Promoting Safe Storage
Mar 2, 2018
The Relationship Between Mental Health Care Access and Suicide
Mar 2, 2018
The Relationship Between Firearm Prevalence and Violent Crime
Mar 2, 2018
The Challenges of Defining and Measuring Defensive Gun Use
Mar 2, 2018
Firearm and Ammunition Taxes
Apr 15, 2021
Methodological Challenges to Identifying the Effects of Gun Policies
Mar 2, 2018