Rates of drug overdose deaths decreased in the United States for the first time since the COVID-19 pandemic began, according to new federal data published early Thursday.

The rate of overdose deaths fell from 32.6 deaths per 100,000 people in 2022 to 31.3 per 100,000 people in 2023, a 4% decrease, according to the report from the Centers for Disease Control and Prevention’s National Center for Health Statistics.

Dr. Aitzaz Munir, an assistant professor of psychiatry at Rutgers New Jersey Medical School and associate program director for the Rutgers Addiction Medicine Fellowship Program, told ABC News the drop in the overdose death rate was “surprising” to him but a positive sign.

He said he believes the decrease in deaths may be due to a more “aggressive approach” toward the treatment of drug conditions including more treatment programs and making them more widely available.

This includes making naloxone, an overdose reversal drug, more widely available and increasing the availability of drug checking supplies, including fentanyl test strips.

“So, there might be a better response in places where these treatments are available and patients are getting those treatments,” he said. “Treatment for addiction works, and if we are seeing this result that there’s a decrease in death rates, that is because of the treatment the patients are getting.”

Dr. Magadelna Cerdá, a professor in the department of population health and director of the center for opioid epidemiology and policy at New York University Grossman School of Medicine, said the drop may also be linked to a decrease in the fentanyl supply.

Fentanyl has been associated with an increase in overdose deaths over the last several years. It is up to 50 times more potent than heroin and 100 times more potent than morphine, and can be deadly even in small doses, according to the CDC.

She said the U.S. Drug Enforcement Agency announced last year that the potency of fentanyl pills agents have been seizing was decreasing, which may be contributing to the decline.

“As the drug supply has become more saturated with fentanyl, good drug supply may be becoming more stable, and people may be just developing a tolerance for fentanyl,” Cerdá said.

The report found that West Virginia was the state with the highest rate at 81.9 deaths per 100,000 while Nebraska had the lowest rate at 9.0 deaths per 100,000.

Additionally, between 2022 and 2023, rates of drug overdose deaths decreased in 20 states and did not change significantly in 25 states.

Meanwhile, over that same period, increases were seen in six states: Alabama, Alaska, California, Nevada, Oregon and Washington.

Cerdá said one hypothesis is that the increase in overdose death rates in western states may be due to shifts in the drug market.

“We saw that the penetration of fentanyl really started in the East Coast,” she said. “Over time, we saw a shift in the drug supply where fentanyl actually has started to enter the western drug markets … we also see a recent increase in counterfeit pills containing fentanyl, which has also infiltrated the drug market.”

Nationwide, the overdose death rate from any opioid decreased from 25 deaths per 100,000 in 2022 to 24 deaths per 100,000 deaths in 2023. The death rate from synthetic opioids other than methadone — which includes fentanyl — fell as well from 22.7 deaths to 22.2 deaths per 100,000.

Meanwhile, the overdose death rate for psychostimulants with abuse potential, which includes methamphetamine, increased from 10.4 deaths per 100,000 in 2022 to 10.6 deaths in 2023. The death rate for cocaine also increased from 8.2 deaths per 100,000 to 8.6 over the same period.

“We should celebrate the decline in overdose deaths, particularly in some of those areas which have historically been most hard hit by this epidemic,” Cerdá said. “And we should invest resources and trying to figure out why the decrease is happening, and how can we learn, particularly from those states that are experiencing this decrease to proactively respond to those states which are currently experiencing an increase.”