The opioid epidemic is pushing down the life expectancy in the US, new research says. Once a leader in longevity, the US has dropped behind most other high-income countries — due in large part to accidental deaths from prescription and illicit opioids that are sweeping the country.

The average lifespan in the US actually increased by two years between 2000 and 2015( from 76.8 years to 78.8 years), but that increase is lower than it should be. That’s in part because deaths from opioid overdoses more than tripled in that same time, according to a study published today in the Journal of the American Medical Association. The Centers for Disease Control and Prevention has called the opioid epidemic "unprecedented in scope."

From 1970 to 2000, life expectancy in the US rose by about 2.5 months every year. If that rate had kept up, people born in the US since 2015 should expect to live longer than 79 years. But the annual increase in life expectancy slowed starting in 2000, and stopped altogether in 2014. That’s mostly because the rising death rate from drug overdoses shaved more than three months off life expectancy in 2015. Three months may not seem like much, but that’s roughly the same reduction attributable to rising death rates from injuries, Alzheimer’s, suicide, chronic liver disease, and sepsis combined.

To figure out what accounted for the slowdown, scientists with the CDC analyzed information from death certificates registered in each state. They figured out causes of death, death rates, and life expectancy. There was some good news: death rates from heart disease, cancer, strokes, the flu, kidney disease, and lung diseases had dropped.

But deaths from drug overdoses had skyrocketed — more than 52,000 people died of overdoses in 2015, up from more than 17,000 people in 2000 — and most of that increase was from unintentional opioid-related deaths. That number could be even higher, the study authors write, because death certificates don’t record the drug responsible for an overdose as much as 25 percent of the time.

The findings echo previous analyses of the CDC’s mortality data by The Washington Post, which found rising death rates for people between the ages of 25 and 44 in nearly every state, for almost all races and ethnicities. “After a century of decreases, the overall death rate for Americans in these prime years rose 8 percent between 2010 and 2015,” the Post reported. The increase was primarily due to overdose deaths and alcohol abuse — and experts say that Fentanyl, a powerful synthetic opioid, is largely to blame.

Last month, President Donald Trump said he was going to declare the opioid crisis a national emergency, which would unlock funds and resources to help states deal with the epidemic. The administration has yet to file the paperwork.