Table 1.

Strength of Evidence Across Gun Policies and Outcomes

Outcome	Minimum Age Requirements		Prohibitions Associated with Mental Illness	Prohibitions Associated with Domestic Violence	Surrender of Firearms by Prohibited Possessors	Extreme-Risk Protection Orders	Back-ground Checks		Licensing and Permitting Requirements	Waiting Periods	Firearm Safety Training Requirements	Lost or Stolen Firearm Reporting Requirements	Firearm Sales Reporting, Recording, and Registration Requirements	Bans on the Sale of Assault Weapons and High-Capacity Magazines	Bans on Low-Quality Handguns	Stand-Your-Ground Laws	Child-Access Prevention Laws	Concealed-Carry Laws		Gun-Free Zones	Laws Allowing Armed Staff in K–12 Schools
	Purchasing	Possessing					Dealer	Dealer and Private										Shall Issue	Permitless Carry
Suicide
Total suicides	↓La	I	I	I		↓L	I	I	I	↓L				I	I	I	↓M, Ib	I	I
Firearm suicides	↓Sc	↓Lc	I	I	I	↓L	I	I	I	↓M			I	I	I	I	↓S, Ib	I	I
Violent crime			↓L		I		I									↑L	I	↑S		I
Total homicides	I	I	I	↓L	I	I	I	↓M	I	↓M	I			I	I	↑S	I	↑S	I
Firearm homicides	I	I	I	↓L	I	I	↓M	↓L	I	↓L			I	I	I	↑S	↓Sd	↑S	I
Intimate partner homicides				↓M, ↑L, Ie	I, ↓Lf					I
Robberies		I		I	I											I	I	↑L
Assaults		I		I	I											I	Id	↑M
Rapes		I		I	I												I	I
Unintentional injuries and deaths		I																I
Unintentional firearm injuries and deaths		I				I											↓L, ↓Sg	I
Mass shootings	I			I	I	I	I	I	↓L	I	I		I	I, ↓Lh		I	I	I	I
Police shootings								I						I					↑L
Defensive gun use																I
Hunting and recreation
Gun industry
Firearm ownership										I						I		I
Firearm manufacturers or retailers							I		I	I				I			I
Firearm purchases									I	I	I		I		I	I		Ii	I
Prices or sales of banned firearms in the short term														↑L

NOTE: I = inconclusive; L = limited; M = moderate; S = supportive. When we identified no studies that met eligibility criteria, cells are blank. ↑ = the policy increases the outcome; ↓ = the policy decreases the outcome.

^aWe concluded that there is limited evidence that higher minimum age requirements for purchasing a handgun may reduce suicides among young adults.

^bWe found moderate evidence for reductions in total suicides among youths, and we found supportive evidence for reductions in firearm suicides and firearm self-injuries among youths. Evidence for effects on outcomes among the full population was inconclusive.

^cWe concluded that there is moderate evidence that minimum age requirements for purchasing a firearm decrease firearm suicides among young people and limited evidence that minimum age requirements for possessing a firearm decrease firearm suicides among young people.

^dWe found supportive evidence that child-access prevention laws reduce firearm homicides or firearm assault injuries among young people. Evidence for effects on outcomes among the overall population was inconclusive.

^eWe concluded that there is moderate evidence that laws establishing firearm prohibitions for individuals subject to domestic violence restraining orders decrease total and firearm-related intimate partner homicides, there is limited evidence that prohibitions associated with stalking misdemeanors increase total intimate partner homicides, and there is inconclusive evidence for how firearm prohibitions for those convicted of stalking or misdemeanor domestic violence affect total and firearm-related intimate partner homicides.

^fWe found inconclusive evidence for the effects of firearm-surrender laws alone but moderate evidence that firearm-surrender laws, when paired with expansions of prohibited-possessor classes, reduce firearm-involved intimate partner homicides. We found limited evidence that firearm-surrender laws, when paired with expansions of prohibited-possessor classes, reduce all intimate partner homicides.

^gWe concluded that there is supportive evidence that child-access prevention laws decrease unintentional firearm injuries and deaths among children and limited evidence that they decrease such injuries and deaths among adults.

^hWe found inconclusive evidence for the effects of assault weapon bans on mass shootings and their fatalities and limited evidence that bans on high-capacity magazines reduce mass shootings and fatalities.

ⁱWe found inconclusive evidence for the effects of may-issue, shall-issue, and permitless-carry laws on firearm purchases.