Conservative state policies regarding the environment, gun safety, labor, taxes and tobacco have been associated with higher mortality rates among working-age people relative to liberal policies, according to new research in PLOS-ONE.

The study, "U.S. state policy contexts and mortality of working-age adults," was co-authored by University Professor Jennifer Karas Montez and Shannon Monnat, professor of sociology.

Montez tells NBC News the researchers focused on working-age people because that group seems to be driving down average U.S. life expectancy. "This age group seems to be experiencing particularly alarming trends in their risk of death, so we wanted to understand why," she says.

Montez says the prevailing explanation for this trend has previously centered on opioid use and business closures. "This analysis points to another major player, and that’s state policymakers," she says. "Policymakers may not feel that they’re responsible for our health or think that they’re responsible for our health, but the reality is every decision that they make affects our health and our risk of dying prematurely."