Suicide rates in rural areas have long outstripped urban suicide rates, and a new study suggests one major reason why: guns.

In a study published Thursday in the American Journal of Public Health, researchers at Johns Hopkins Bloomberg School of Public Health examined more than 6,000 suicides in Maryland between 2003 and 2015, roughly half of which were committed using a firearm. The least populous areas of the state had a suicide rate of more than 24 deaths per 100,000 people, which is about 35 percent higher than the rate in the state’s most metropolitan areas.

But when the researchers factored out the suicides committed using guns, the suicide rate in rural areas fell dramatically, indicating that the difference between the two areas could be attributed to gun access.

“It is often said that people would kill themselves anyway, even if they didn’t have access to guns,” Paul Sasha Nestadt, who led the study, said in a statement. “There is an entire body of research that tells us that is simply not true.”

That body of research is enormous, with dozens of studies confirming a strong link between gun access and a heightened risk of suicide. Several studies suggest that a family living in a home with a gun in it has a risk of suicide anywhere between 2 to 10 times the risk for families living in firearm-free homes.

Suicide rates are also increasing in all age groups below 75 and in nearly all racial and ethnic groups in the United States, according to the Centers for Disease Control and Prevention. While firearms are not the most commonly used method to commit suicide, they are much more lethal than the two most frequent means — drugs and “cutting”.