Chinese crackdowns on chemicals used to make illicit fentanyl may have played a significant role in the sharp reduction of U.S. overdose deaths, according to research published Thursday.
The paper suggests that the illicit fentanyl trade — which drove a historic surge in drug deaths during the past decade — experienced a large-scale decline in supply. Overdose deaths had surpassed 100,000 annually during the Biden administration, but began to decline in mid-2023 and plunged further in its final year. They have kept falling under President Donald Trump, who invokes drug trafficking as he imposes steep tariffs on other countries and unleashes missile strikes on suspected drug boats in the Caribbean.
The research, published Thursday in the journal Science, adds to debates among government officials, public health researchers and addiction experts over the complex reasons for the precipitous drop in deaths.
They have also pointed to billions spent on addiction treatment, the overdose reversal drug naloxone and law-enforcement actions that disrupted traffickers domestically and abroad. Researchers in the Science paper stressed that those factors have been crucial in saving lives but emphasized the importance of efforts to prevent fentanyl from even being manufactured.
In suggesting a major disruption in the fentanyl trade “possibly tied to Chinese government actions,” researchers also analyzed death trends in Canada, the purity of seized fentanyl and online posts about shortages of the drugs.
“This demonstrates how influential China can be and how much they can help us — or hurt us,” said Keith Humphreys, a co-author of the paper and former White House drug policy adviser under President Barack Obama.
U.S. government and law enforcement agencies have long scrutinized the role China’s chemical and pharmaceutical industries played in the international fentanyl trade.
China agreed to internal restrictions on fentanyl-related substances during the first Trump administration. But that led to Mexican criminal groups synthesizing illicit fentanyl in secret labs in Mexico with precursor chemicals bought from companies in China. Since 2023, the Chinese government has shut down some of those companies as part of a broader crackdown.
The Drug Enforcement Administration, in its latest annual drug intelligence report, noted that some China-based chemical suppliers are wary of supplying them to international customers, “demonstrating an awareness on their part that the government of China is controlling more fentanyl precursors.”
According to state data compiled by the Centers for Disease Control and Prevention, estimated drug deaths plummeted in 2024 to about 81,711, of which 49,241 involved synthetic opioids such as fentanyl. Estimates for 2025 won’t be published for several months, but researchers believe the decline is continuing.
The Science researchers caution that the precise scope of China’s crackdown is difficult to assess, given the opacity of enforcement in the country. China’s cooperation with U.S. drug authorities on fentanyl has long been fragile, often collapsing when broader tensions flare.
That changed ahead of a November 2023 summit between President Joe Biden and Chinese leader Xi Jinping, when the two governments agreed to launch a multiagency crackdown on Chinese chemical suppliers tied to the fentanyl trade. Chinese authorities subsequently arrested about 300 people and moved to restrict roughly 55 additional synthetic substances — steps Beijing had previously resisted.
The summit, however, happened months after overdose deaths had already begun to fall — a timing mismatch the researchers acknowledge. Humphreys theorizes China may have begun crackdowns months earlier before the agreements were announced.
Other researchers are skeptical. Vanda Felbab-Brown, a senior fellow at the Brookings Institution specializing in security and counternarcotics, noted that when overdoses began to fall, tensions between Washington and Beijing remained high over issues of trade, technology and security. Beijing would want to trumpet its enforcement, she said.
In a statement, the Chinese embassy said the country’s broad efforts to combat the spread of deadly synthetic drugs has achieved “remarkable results.”
The embassy said that between October 2023 and August 2025, the Chinese government has shut down 286 companies and forced more than 500 to delete information on chemical sales. About 160,000 ads have been removed in that time, the statement said.
“China has been helping the U.S. tackle the fentanyl issue and is willing to continue the cooperation on the basis of equality and mutual respect,” the embassy said.
The Science paper does not account for how overdose death rates fell in parts of the U.S. first, or how fatalities in more populous states can skew national statistics, said Nabarun Dasgupta, an epidemiologist at the University of North Carolina at Chapel Hill. He said fentanyl habits have been changing as fewer people start using it, and many users are cutting back or no longer using alone.
“It’s not a straight line between drug supply and overdose deaths because of protective behaviors that have been adopted in between,” Dasgupta said.
In trying to determine reasons for the sharp decrease in deaths, researchers pointed out that purity of fentanyl seizures tested by the DEA dropped around the same time U.S. deaths were falling. Seizures fell too, an indication of reduced supply, they said.
Researchers also analyzed posts on Reddit, the online forum where users often post about the illicit drug market. They noted a spike in mentions of fentanyl shortages in the middle of 2023, “roughly coinciding with the beginning of the decline in fatal overdoses,” researchers wrote.
Researchers also analyzed fentanyl trends in Canada where criminal groups there also secure precursor chemicals from China.
Canada has typically embraced a more public health centered approach to combating the opioid epidemic than the U.S. — for example, authorizing numerous centers where users can consume drugs under supervision. Still, deaths began falling around the same time, researchers said. Chinese crackdowns may explain the “parallel mortality declines,” the authors of the Science paper said.
“What’s really striking is that parallel across the two countries, even though the two countries have very different domestic policies,” Jonathan P. Caulkins, a Carnegie Mellon University professor who researches the criminal drug trade and was a study co-author.
Inside China, sellers of chemicals have offered mixed message on the impacts of the 2023 measures. They said there is heightened oversight of scheduled substances and online advertising but enforcement varies widely by locality.
Some companies left the business after 2023, said one Hubei-based employee at a chemical manufacturer, whose products can be used to make fentanyl and who spoke on the condition of anonymity to talk candidly about the industry.
Asked whether the company is still able to sell controlled chemicals to customers, including those in Mexico, the employee said those sales persist.
“We don’t sell much any more because the company focus has changed,” the person said, but “it’s not much trouble to do that.”
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