Suicide rates are on the rise in America, particularly in rural communities, according to a new study.

Death by suicide among Americans aged 25 to 64 rose between 1999 and 2016, researchers found in a report published in JAMA Network Open on Friday. That rare increased more in rural counties than in major metropolitan areas.

Between 1999 and 2016, there were 453,577 suicides among Americans ages 25 to 64. The the last three years of the study witnessed higher annual figures than the previous years.

The majority of the deaths were male. The deaths were more common among middle-aged adults than younger and older adults.

The study relied on statistics from the National Vital Statistics System, a database that includes information on suicide deaths, including year of death, gender, age, and county of residence, as well as the US Census, the American Community Survey, County Business Patterns, Area Health Resource Files, and the North American Industry Classification System.

Danielle Steelesmith, the lead author of the study, said poverty, low income, and underemployment among the factors that appear to be driving these rates up. She notes that these factors are “really bad” in rural areas.

High levels of social fragmentation and a high percentage of veterans, both more pronounced in rural areas, were also contributors.

In all counties except for the most rural ones, the presence of gun shops was also associated with an increase in suicide rates. In 2017, suicides accounted for six in 10 gun deaths in the US.

In the researchers’ conclusion, they wrote that: “This study found that suicide rates have increased across the nation and most rapidly in rural counties, which may be more sensitive to the impact of social deprivation than more metropolitan counties.

“Improving social connectedness, civic opportunities, and health insurance coverage as well as limiting access to lethal means have the potential to reduce suicide rates across the rural-urban continuum.”