Handguns on display at the 2013 New York State Arms Collectors Association Albany Gun Show in Albany, N.Y. (Philip Kamrass/AP)

States that have more relaxed criteria for allowing residents to carry concealed handguns have a higher rate of gun deaths than states with stricter requirements, according to a study released Thursday.

Researchers at the Boston University School of Public Health found that states that have “may issue” laws — which give law enforcement officials wide discretion to decide who can receive a concealed carry permit — have lower gun death rates than states that call for little discretion once basic criteria for obtaining the permit is met, also known as “shall issue” laws.

The study found that states with shall-issue laws had handgun homicide rates that were 10.6 percent higher than may-issue states. Additionally, shall-issue states had firearm homicide rates that were 8.6 percent higher and overall homicide rates that were 6.5 percent higher than may-issue states.

On opposite ends of the spectrum, Louisiana, a shall-issue state, had a firearm homicide rate of 9.96 per 100,000 residents in 2015; Hawaii, a may-issue state, had a firearm homicide rate of 0.75 per 100,000 residents in 2015.

“There is clearly a trend that's going on nationally toward more and more lenient concealed carry laws over time, with less and less discretion for law enforcement,” said Michael Siegel, a professor at the Boston University School of Public Health and the study’s main author. “Based on the findings of our paper, that suggests it is putting the public safety at risk.”

Nine of the states studied had may-issue laws and 37 states had shall-issue laws. Four states had what is known as “permitless carry” laws, which allow residents to carry weapons out of sight without a license, but states with those laws were not included in the analysis.

The may-issue states had varying criteria to approve or deny a concealed carry permit. California requires that its applicants be of “good moral character” and have “good cause” for the permit. Hawaii requires applicants to have an exceptional case that shows they fear injury or damage to their property. In New Jersey, a person must demonstrate a justifiable need to hide a handgun and submit three references who have known the applicant for at least three years and can vouch that he or she is “a person of good moral character and behavior.”

Siegel said a number of states changed their laws to the looser restrictions during the course of the study, a change that was taken into account as part of the analysis.

“There has been a really tremendous trend in weakening of these laws over time,” he said. “There was no state that strengthened.”

The study comes as more states are completely doing away with concealed carry regulations and Congress is debating whether to allow state concealed carry permits to apply across state lines.

Bills in both the Senate and House would allow people who received a concealed carry permit in their home state to travel to another state with their gun, as long as they abide by the laws in that state. The proposal is known as “concealed carry reciprocity.” The Senate bill is sponsored by Sen. John Cornyn (R-Tex.) and the House bill by Rep. Richard Hudson (R-N.C.)

“Concealed carry reciprocity legislation recognizes that Americans’ Second Amendment right to bear arms doesn’t end at their states’ borders,” the National Rifle Association Institute for Legislative Action, which supports the federal legislation, said in a statement posted on the organization’s website. “This legislation would ensure that states would have to treat lawful concealed carriers from other states the same as lawful in-state concealed carriers.”

Tim Schmidt, president and founder of the United States Concealed Carry Association, said he expects people who live in places with strict gun laws and high homicide rates to take issue with the study.

“The reality is that concealed carry permit holders are responsible citizens, who have proven they are willing to comply with the law, while criminals who commit murder don’t care what the laws are in their states because they’re criminals,” he said in a statement.

At least 12 states allow residents to carry concealed handguns without a permit, something known as “Constitutional carry” or “permitless carry.” Gun rights advocates see the laws as the next frontier in Second Amendment rights, arguing that the Constitution is all the permission needed to carry handguns out of sight.

The District’s strict concealed carry laws were relaxed last month after a court struck down its requirement that people demonstrate a “good reason” -- such as fear of violence -- why they want to carry a weapon out of sight. District Attorney Karl A. Racine did not appeal the ruling out of fear that the case would end up in the U.S. Supreme Court.

New Hampshire Gov. Chris Sununu (R) signed a law in February allowing anyone who has purchased a licensed pistol or revolver to carry it, loaded or unloaded, on him or herself or in a vehicle. North Dakota Gov. Doug Burgum (R) signed a law in March allowing adults who have been a resident of the state for at least a year to carry a weapon without a concealed weapon license if they meet certain criteria; convicted felons and those addicted to drugs are excluded, among others.