The decline in U.S. drug overdose deaths appears to have continued this year, giving experts hope the nation is seeing sustained improvement in the persistent epidemic.

There were about 97,000 overdose deaths in the 12-month period that ended June 30, according to provisional Centers for Disease Control and Prevention data released Wednesday. That’s down 14% from the estimated 113,000 for the previous 12-month period.

“This is a pretty stunning and rapid reversal of drug overdose mortality numbers,” said Brandon Marshall, a Brown University researcher who studies overdose trends.

Overdose death rates began steadily climbing in the 1990s because of opioid painkillers, followed by waves of deaths led by other opioids like heroin and — more recently — illicit fentanyl. Provisional data had indicated a slight decline for 2023, and the tally released Wednesday showed that the downward trend has kept going.

Of course, there have been moments in the last several years when U.S. overdose deaths seemed to have plateaued or even started to go down, only to rise again, Marshall noted.

“This seems to be substantial and sustained,” Marshall said. “I think there’s real reason for hope here.”

Experts aren’t certain about the reasons for the decline, but they cite a combination of possible factors.

One is COVID-19. In the worst days of the pandemic, addiction treatment was hard to get, and people were socially isolated — with no one around to help if they overdosed.

“During the pandemic we saw such a meteoric rise in drug overdose deaths that it’s only natural we would see a decrease,” said Farida Ahmad of the CDC’s National Center for Health Statistics.

Still, overdose deaths are well above what they were at the beginning of the COVID-19 pandemic.

The recent numbers could represent the fruition of years of efforts to increase the availability of the overdose-reversing drug naloxone, and addiction treatments such as buprenorphine, said Erin Winstanley, a University of Pittsburgh professor who researches drug overdose trends.

Marshall said such efforts likely are being aided by money from settlements of opioid-related lawsuits, brought by state, local and Native American governments against drugmakers, wholesalers and pharmacies. Settlement funds have been rolling out to small towns and big cities across the U.S., and some have started spending the money on naloxone and other measures.

Some experts have wondered about changes in the drug supply. Xylazine, a sedative, has been increasingly detected in illegally manufactured fentanyl, and experts are sorting out exactly how it’s affecting overdoses.

In the latest CDC data, overdose death reports are down in 45 states. Increases occurred in Alaska, Nevada, Oregon, Utah and Washington.

The most dramatic decreases were seen in North Carolina and Ohio, but CDC officials voiced a note of caution. Some jurisdictions have had lags in getting death records to federal statisticians — particularly North Carolina, where death investigations have slowed because of understaffing at the state medical examiner’s office. The CDC made estimates to try to account for incomplete death records, but the decline in some places may ultimately turn out not to be as dramatic as initial numbers suggest.

Another limitation of the provisional data is that it doesn’t detail what’s happening in different groups of people. Recent research noted the overdose deaths in Black and Native Americans have been growing disproportionately larger.

“We really need more data from the CDC to learn whether these declines are being experienced in all racial ethnic subgroups,” Marshall said.