Trump and RFK Jr. promoted this unproven cure for autism. Some parents listened

Last September, President Donald Trump, Robert F. Kennedy Jr. and other health officials announced that they had discovered a new, potentially groundbreaking treatment for autism spectrum disorder (ASD): the existing drug leucovorin. Today’s survey shows that many families believed them.

Researchers at the University of California, San Diego examined prescribing trends for the drug across the country last year. Prescribing rates for leucovorin among children with autism rose sharply through the end of 2025, especially after the September announcement, they found. The results show that Trump’s endorsement had a significant impact on these families, the researchers said, despite a lack of data supporting the drug’s effectiveness.

« Families of children with ASD often seek therapies that could improve quality of life, especially when treatment options are limited, » study lead author Joshua Rothman, clinical assistant professor of pediatrics at the UCSD School of Medicine, told Gizmodo. « Although some small studies are promising, we do not yet have strong evidence to recommend this treatment for all children with ASD. »

Trump’s blow

The announcement last September largely focused on acetaminophen (Tylenol). At the time, Trump and other officials announced they had discovered a link between women taking acetaminophen during pregnancy and a higher risk of autism in their children. Many experts disagree with this claim, and newer studies continue to find evidence against it. During the same press conference, Trump officials touted leucovorin as a treatment for autism.

Leucovorin is a form of folic acid, or B9, a vitamin important for many functions, including healthy fetal development. Although traditionally used to offset the side effects of some cancer treatments, it has also become a standard treatment for cerebral folate deficiency, a condition in which folic acid cannot be transported to the brain by normal means. Unlike other forms of folate, such as folic acid, leucovorin can reach the brain, allowing it to reverse this deficiency.

Limited research suggests that children with autism likely have low levels of folate in their brains, and some of the symptoms of brain folate deficiency may also mimic severe autism. Based on these tenuous ties, RFK Jr. said in September that leucovorin is an exciting therapy that may benefit « a large number of children » with autism. Former FDA Commissioner Marty Macari, who resigned last week, even said that leucovorin could help « hundreds of thousands of children. » At another point, he suggested that leucovorin could treat up to « 50% of autistic children » who may have this deficiency.

Given the widespread attention the September announcement attracted, Rothman and his team wanted to see how it might have changed the use of leucovorin. They analyzed medical records from EPIC Cosmos, a database containing more than 300 million patient records collected by US health care systems. They specifically tracked leucovorin prescription rates among more than 800,000 children diagnosed with autism between January 2023 and January 2026.

Trump’s announcement wasn’t the only big thing in 2025 that potentially boosted leucovorin’s popularity. A February 2025 Fox News report detailed several families who believed the drug improved their children’s symptoms, particularly their speech deficits.

Rothman and his team saw a clear jump in leucovorin prescription rates after the Fox News report, followed by an even bigger jump after Trump’s announcement. The rate in 2023 and 2024 was about 34 prescriptions for every 100,000 outpatient visits among children with autism. By November 2025, however, the number of prescriptions had risen to 835 per 100,000 visits.

« We found that prescriptions of leucovorin for children with ASD increased by more than 2,000% following extensive media attention and public statements by White House officials, » Rothman said. The team’s findings were published Monday in JAMA Network Open.

A drug without strong data

After the announcement in September, the Trump administration backtracked on its bombastic approval 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 specifically refused to approve it as an autism treatment, with FDA officials specifically citing a lack of strong evidence to support the decision.

Credible evidence supporting leucovorin for autism has always been weak, and has recently become weaker. Last January, a journal yanked a positive trial testing leucovorin supplements in children with autism after outside researchers found numerous « errors » and « concerns » with the data, according to the retraction notice. It was the largest trial of the drug ever conducted, with 77 children, and one of five trials in total.

Rothman and his team’s study did not aim to assess the usefulness of leucovorin for autism. But given how many families have already been prescribed the drug, more research needs to be done on the topic, Rothman said.

« Because leucovorin prescriptions have increased so significantly for children with ASD, it would be useful to evaluate the results and share those results, » he said. So the team hopes that other researchers will be able to follow the long-term outcomes of families and children who took leucovorin for autism.

« It is our duty as scientists and clinicians to generate the rigorous data needed to help families and clinicians make informed decisions, » he added.