Researchers at the University of California, San Diego examined nationwide prescription trends for the drug last year. They found that prescription rates of leucovorin in children with autism skyrocketed by the end of 2025, especially after the September announcement. The researchers say the results indicate that Trump’s support had a significant impact on these families, despite the lack of data supporting the drug’s effectiveness.
“Families of children with ASD are often looking for treatments that can improve quality of life, especially when treatment options are limited,” study lead author Joshua Rothman, a clinical assistant professor of pediatrics at UCSD’s School of Medicine, told Gizmodo. “Although some small studies have shown promise, we do not yet have strong evidence to recommend this treatment to all children with ASD.”
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The announcement last September focused primarily on acetaminophen (Tylenol). At the time, Trump and other officials announced the discovery of a link between women who took acetaminophen during pregnancy and a higher risk of autism in their children. Many experts disagreed with this claim, and recent studies have continued to find evidence against it. During the same press conference, Trump officials introduced leucovorin as a treatment for autism.
Leucovorin is a form of folate, or B9, a vitamin important for many functions, including healthy fetal development. Although traditionally used to relieve the side effects of some cancer treatments, it has also become a standard treatment for cerebral folate deficiency – a condition where folate cannot be delivered to the brain through normal means. Unlike other forms of folate, such as folic acid, leucovorin can reach the brain, thereby correcting this deficiency.
Limited studies have shown that children with autism are likely to have low folate levels in the brain, and some symptoms of cerebral folate deficiency may even resemble those of severe autism. Based on these weak connections, RFK Jr. claimed in September that leucovorin was an exciting therapy that could benefit “a large number of children” with autism. Former FDA Commissioner Marty Macri, who resigned last week, even said that leucovorin could potentially help “hundreds of thousands of children.” At another time, he said that leucovorin could treat “50% of children with autism” who may have this deficiency.
Given the widespread attention the September announcement attracted, Rothman and his team wanted to see how this might change the use of leucovorin. They analyzed medical records from EPIC Cosmos, a database that contains more than 300 million patient records collected from health care systems across the US. They specifically tracked prescription rates of leucovorin among more than 800,000 children with autism between January 2023 and January 2026.
Trump’s announcement wasn’t the only big thing to potentially boost leucovorin’s popularity in 2025. A Fox News report in February 2025 detailed several families who believed the drug improved their children’s symptoms, particularly their ability to speak.
Rothman and his team observed a clear spike in leucovorin prescription rates in the wake of the Fox News report, followed by an even larger increase after Trump’s announcement. The rate was about 34 prescriptions per 100,000 outpatient visits among children with autism in 2023 and 2024. However, by November 2025, this had increased to 835 prescriptions per 100,000 visits.
“We found that leucovorin prescriptions for children with ASD increased by more than 2,000% following widespread media attention and public statements from White House officials,” Rothman said. The team’s results were published Monday in JAMA Network Open.
A drug without solid data
Since the September announcement, the Trump administration has walked back its vigorous support of the drug.
In early March, the Food and Drug Administration officially approved the expanded use of leucovorin to treat cerebral folate deficiency. But the agency declined to specifically endorse it as a treatment for autism, with FDA officials apparently citing a lack of strong evidence that would support the decision.
Reliable data supporting leucovorin for autism has always been weak, and it has become weaker recently. Last January, a journal published a positive report testing leucovorin supplements in children with autism, after external researchers discovered several “errors” and “concerns” with the data. It was the largest trial of the drug to date, testing 77 children, and one of only five trials overall.
The purpose of Rothman and his team’s study is not to consider the utility of leucovorin for autism. But given how many families are now prescribed the drug, more research should be done on the topic, Rothman argues.
“Since leucovorin prescriptions for children with ASD have increased significantly, it would be worthwhile to assess outcomes and share these results,” he said. So the team hopes that other researchers will be able to track the long-term outcomes of families and children who have taken leucovorin for autism.
“It is our duty as scientists and physicians to generate the rigorous data needed to help families and physicians make informed decisions,” he said.
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