(CNN)Drug overdose deaths in the United States declined 5.1% in 2018, according to preliminary data released Wednesday by the US Centers for Disease Control and Prevention’s National Center for Health Statistics.

The slight decline in drug overdose deaths marked the first such drop in decades.

“The reason to be hopeful is that for the past 25 years every year we experienced an increase in overdose deaths. This is the first time in 25 years that overdose deaths will not have increased and have come down a little bit,” said Dr. Andrew Kolodny, co-director of Opioid Policy Research at Brandeis University in Massachusetts. Kolodny was not involved in the new data.

The National Center for Health Statistics estimates there were 68,557 drug overdose deaths in 2018. An estimated 47,590 involved opioids, and 31,897 involved synthetic opioids, such as fentanyl and tramadol.

The data will not be finalized until next year.

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“There’s light at the end of the tunnel,” Kolodny said, but he added, “there’s certainly nothing to celebrate because even with the slight reduction we’re still experiencing an enormous death toll.”

Additionally, “when you look at the national data, it masks what’s happening on a regional level and on a state level,” he said.

For instance, the mortality rate from synthetic opioids in 28 states more than doubled every two years from 1999 to 2016, according to a study published in the medical journal JAMA Network Open in February. At the national level, opioids were responsible for shaving 0.36 years off Americans’ life expectancy in 2016, the study said. That’s a greater loss of life than caused by guns or motor vehicle accidents.

Opioid prescribing has dropped since the CDC issued opioid prescribing guidelines in early 2016, which resulted both in doctors prescribing fewer opioids as well as insurers providing less coverage for opioids. Many experts have pointed to the overprescribing of painkillers as the root of the US opioid crisis, but say it then evolved into a heroin crisis and a fentanyl crisis.

In a statement, US Health and Human Services Secretary Alex Azar said that the Trump administration’s efforts and community responses around the United States had increased the number of patients receiving medication-assisted treatment and overdose-reversing drugs, while opioid prescriptions had fallen.

“The latest provisional data on overdose deaths show that America’s united efforts to curb opioid use disorder and addiction are working. Lives are being saved, and we’re beginning to win the fight against this crisis,” Azar said.

“While the declining trend of overdose deaths is an encouraging sign, by no means have we declared victory against the epidemic or addiction in general. This crisis developed over two decades and it will not be solved overnight.”

CNN’s Nadia Kounang contributed to this report.

This story first appeared July 17, 2019, in CNN Health | by Ben Tinker, Jacqueline Howard and Jamie Gumbrecht, CNN