(Reuters Health) - U.S. states with the strongest firearm laws have fewer gun-related murders and fewer suicides than states that take a more permissive approach to regulating these weapons, a new study suggests.

Counties in states with strong gun laws had lower rates of firearm homicides than counties in states with weak laws, the study found.

In states with weak laws, counties had lower gun murder rates only if neighboring states had strict regulations in place.

But states with strong gun laws had lower firearm and overall suicide rates regardless of the strength of laws in bordering states.

“This means that strong laws in one state may have a protective effect across state lines,” lead study author Dr. Elinore Kaufman of NewYork-Presbyterian/Weill Cornell Medical Center said by email.

“The majority of suicides involve guns and the majority of gun deaths are suicides,” Kaufman added. “These deaths are tragic and state policy may be able to help prevent them.”

In 3,108 counties in 48 states, researchers examined data from 2010 to 2014 for firearm suicides and homicides.

Each year on average, for every 100,000 people in the population, there were about 10 firearm suicides and more than 2 murders involving guns, researchers report in JAMA Internal Medicine.

They also scored state gun control laws, awarding up to 12 points for regulations like licensing gun dealers and purchasers, requiring background checks for private gun sellers, mandating prompt reporting of stolen firearms, and limiting how many guns one person can buy at once or over a certain period of time.

Researchers also ranked states based on the strength of laws in neighboring states, to see if this might impact what happened to suicide or murder rates.

California had the strongest firearm control laws, with a score of 10, but many counties in California are also adjacent to states with weak regulations.

Compared with counties in states with tough laws that bordered states with strict regulations, counties in states with weak laws that were adjacent to states with weak laws had higher overall and firearm murder rates. But these counties didn’t have higher rates of non-firearm homicides.

By contrast, counties in states with weak laws that bordered states with tough laws didn’t have worse murder rates, with or without guns involved, than counties in states with tough laws that bordered states with strict regulations.

The study wasn’t a controlled experiment designed to prove whether or how specific state gun laws might directly impact suicide or murder rates within that state or a neighboring state. There were also few states with strict laws in the study, which may have limited researchers’ ability to detect an effect for the toughest gun regulations, and researchers also lacked data on the individual effect of specific gun policies.

Even so, the results suggest that laws in one state may have an impact across state lines, said Dr. Robert Steinbrook, editor-at-large for JAMA Internal Medicine.

“Firearms frequently move across state lines, and homicides and other crimes in one state may involve guns from another state,” Steinbrook said by email. “This is an important public health question, because many people live near the border with another state and frequently travel back and forth.”

There still may be variation within states that needs to be explored in greater detail, and it’s also possible that the ways that guns move within states and across state lines may vary across the country, said Alex Piquero, a criminology researcher at the University of Texas at Dallas who wasn’t involved in the study.

“While these results do not call for the elimination of firearms, the results convincingly show that strengthening state firearm policies through a variety of ways reduces both firearms suicides and homicides,” Piquero said by email.

SOURCE: bit.ly/2I82DeA JAMA Internal Medicine, online March 5, 2018.