Updated September 25, 2025 at 12:26 PM CDT
President Trump is promising a new treatment for autism spectrum disorder: a prescription form of vitamin B9 called leucovorin.
But many scientists and medical organizations are skeptical; some families are excited, and many are wary.
"I think that this entire thing has been a bit misleading," says Caitee Donovan, referring to a White House press conference Monday in which Trump and his deputies blamed Tylenol for autism and encouraged the use of leucovorin to treat it.
Donovan's daughter, Scarlett Donovan-New, was diagnosed with autism at 17 months. Donovan, who lives in Mahopec, N.Y., said she was dismayed to hear the president and several high-level health officials extol the benefits of the medication, which is also known as folinic acid.
It's "an exciting therapy that may benefit large numbers of children who have suffered from autism," Health and Human Services Secretary Robert F. Kennedy Jr. said at the event. The treatment "gives hope to the many parents with autistic children," Trump said.
What the Trump administration is offering is a new label on an old product, sanctioning its use for a rare brain condition called cerebral folate deficiency (CFD). The condition's connection to autism remains unclear; a minority of people with autism also have CFD.
Parents like Donovan say the move is just another misguided effort to find a simple solution to a complex disorder, and to suggest that parents could have prevented their child's autism.
A nuanced understanding of autism
Donovan knows well the stresses that many parents of children with autism face. She says when her toddler was diagnosed, "we were told she would never speak."
"A direct quote from the doctor: We'd 'be lucky if she banged her head against a wall,'" Donovan recalls. "That's what we were told."
But now, nine years later, her daughter is thriving.
"She plays flag football. She did cheer for four years. She talks non-stop," Donovan says.
And says it wasn't any drug, but years of therapies — for speech, movement, behavior and even eating — that helped.
Donovan now understands autism is complex, with roots mostly in genetics. But she spent years agonizing whether something she did — or didn't do — might have caused the condition. She says that now she knows better.
"It isn't something I did," Donovan says. "This is just who my daughter is and she's perfect the way she is."
Jax Bayne, an advocate with autism living in Bellingham, Wash., echoed those sentiments.
"I think anybody who's excited about the idea of a treatment or cure for autism has literally no idea or understanding of what autism is," says Bayne, 35.
Most scientists and medical groups agree that autism has many causes.
Genetic factors are the leading contributor and the best understood, they say.
"We know now that there are 100 or more autism genes, and we estimate there's probably about 400," says Jonathan Sebat, who directs the Beyster Center for Psychiatric Genomics at the University of California, San Diego.
The role of other factors — like environmental toxins, events that occur during pregnancy, or cerebral folate deficiency — is still unclear.
But vaccines, which Trump invokes frequently, have been ruled out as a cause of autism.
The case for leucovorin
Until now, leucovorin has been prescribed primarily to protect healthy cells from the toxic effects of methotrexate, a common chemotherapy drug used in cancer care. It was approved for this use in 1983.
Now — at the behest of Trump and with no formal review — the FDA is in the process of changing the product's label. The change will include language indicating that leucovorin can "improve certain symptoms in adults and pediatric patients with cerebral folate deficiency," according to an FDA document published in the Federal Register.
Cerebral folate deficiency (CFD) is a rare condition in which a person's brain isn't getting enough vitamin B9. CFD typically appears before age 2, causing a range of symptoms including intellectual disability, lack of muscle control, and seizures. Some of the symptoms overlap those of autism spectrum disorder.
One scientific review of a very limited range of studies found that 38% of people with autism had antibodies that can lead to CFD. The same review found that treatment with leucovorin "significantly improved communication" in some autistic individuals.
Reviews like this one, which combine data from multiple studies, are prone to bias and are only as good as the underlying research they include.
Also, the potential impact of leucovorin treatment will remain uncertain until scientists establish how many people on the spectrum have CFD, and whether the condition actually causes autism.
CFD occurs when folate, which is important to brain development and function, is unable to reach cells in the brain. Diagnosis requires a spinal tap to measure levels of a form of folate in spinal fluid.
The condition can be caused by genetic mutations or metabolic disorders. But usually the cause is a misguided immune response that keeps folate from entering brain cells.
Leucovorin is a form of folate that can get around those roadblocks.
"It's a bit tough to get really, really excited about what they would call a 'miracle drug,'" says Shelby Smith, a Dallas mother of a 6-year-old autistic son who is considered non-verbal. Parents, she says, are accustomed to being peddled vitamins, supplements, and even fake therapies. "It's always something being pushed," Smith says, which can at times then make symptoms worse.
In infants, leucovorin is most effective when given soon after CFD appears, which can be as early as six months of age, according to the National Organization for Rare Disorders.
The treatment's efficacy in older children or adults with autism is uncertain. But the existing research suggests any benefit will be modest.
For example, a recent 24-week study in India compared 39 autistic children who got leucovorin with 38 who got a placebo.
Both groups raised their scores on a common autism rating scale, which runs from a low of 15 to a high of 60. The children who received the drug improved slightly more than those who didn't (3.6 points vs. 2.4).
In a 12-week study of 48 autistic children done in Little Rock, Arkansas, in 2013, researchers reported that those who got leucovorin improved significantly on a measure of language impairment, while those who got a placebo did not.
Interestingly, the drug seemed to improve language scores even in children who did not appear to have cerebral folate deficiency.
When the results were published in 2016 in the journal Molecular Psychiatry, the authors cautioned that their findings "should be considered preliminary until treatment is assessed in larger multicenter studies with longer duration."
"Jumping the gun"
Given the lack of conclusive evidence, many doctors and researchers think it's too soon to be suggesting leucovorin as a treatment.
Medical and scientific groups say they'd like to see the same sort of research on leucovorin that the FDA requires of other drugs: two large, rigorous clinical trials showing that the product lives up to its label.
The Coalition of Autism Scientists issued a statement saying, "It is premature to claim that leucovorin is an effective treatment for autism."
Alycia Halladay, a biopsychologist and chief science officer of the Autism Science Foundation, agreed.
"They are jumping the gun a little bit," she says.
Halladay is a doctor, parent of a daughter with autism, and chief scientific officer of the Autism Science Foundation. She says the administration is bypassing normal research and safety checks with leucovorin.
"I don't think most people understand the rigor that the FDA normally would apply," she says.
Halladay adds the White House's messaging further confused many families when Mehmet Oz, head of the federal agency that oversees Medicare and Medicaid, promised at the news conference that state Medicaid programs "will cover prescription leucovorin around the country," adding that "it's yours, but you have to go to a doctor and get a prescription."
"It was disingenuous to tell people at the press conference that it was going to be made available to everybody," Halladay said. She says the language issued later shows it will allow leucovorin prescriptions only for that subset of autistic patients with CFD, the vitamin B deficiency.
"I think families should know that, in fact, it's not going to be approved or made available to the wide autism community; it's only going to be made available to those with a documented cerebral folate deficiency," Halladay said.
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