New York, NY (September 22, 2025) We are deeply concerned by today’s announcements from President Trump and HHS Secretary Robert F. Kennedy suggesting that taking acetaminophen (Tylenol) during pregnancy causes autism, that a medicine derived from folate can be used to treat symptoms of autism, and that vaccines should be broken up over multiple visits and MMR broken into separate shots.
“Any association between acetaminophen and autism is based on limited, conflicting, and inconsistent science and is premature,” said Autism Science Foundation Chief Science Officer Dr. Alycia Halladay. “This claim risks undermining public health while also misleading families who deserve clear, factual information. For many years, RFK and President Trump have shared their belief that vaccines cause autism, but this is also not supported by the science, which has shown no relationship between vaccines and autism.”
“We are unsure why this announcement came today and how the conclusions were drawn,” added Alison Singer, President of the Autism Science Foundation. “No new data or scientific studies were presented or shared. No new studies have been published in the literature. No new presentations on this topic were made at scientific or medical conferences. Instead, President Trump talked about what he thinks and feels without offering scientific evidence. He said “tough it out”, meaning don’t take Tylenol or give it to your child. It took me straight back to when moms were blamed for autism. If you can’t take the pain or deal with a fever, then it’s your fault if your child has autism. That was shocking. Simply shocking.”
“What was said today was dangerous”, added Dr. Halladay. “President Trump and Secretary Kennedy downplayed the complexity of autism and suggested that autism rates would decline if pregnant women stopped taking Tylenol and if parents spaced out childhood vaccines. He claimed there were no downsides to these behaviors, which is inconsistent with longstanding public health practices.”
Today’s announcement distracts from the urgent scientific work needed to understand the true causes of autism and to develop better supports and interventions for autistic people and their families. Autism doesn’t have a single cause. It is the result of a complex mix of genetics and environmental factors. We know that genetic factors play the biggest role; hundreds of genes have been linked to autism, and inherited or spontaneous changes in these genes can alter brain development. Environmental factors also matter, especially during pregnancy, such as advanced parental age at conception, prematurity or low birth weight, and exposures that affect brain development, like fever or illness during pregnancy. The best current science shows autism arises from the complex interaction of genetic susceptibility with environmental influences during brain development.
“The Autism Science Foundation strongly supports research into autism’s causes. More research needs to be done before alarming families or suggesting steps that may not actually reduce risk, when we know that NOT treating a fever during pregnancy creates risk. Pregnant women deserve clear, evidence-based guidance – not incomplete conclusions that could erode confidence in safe, beneficial care,” added Dr. Halladay.
Acetaminophen and Autism
The scientific study referred to by RFK, President Trump, and Dr. Bhattacharya in today’s press conference is a systematic review of 6 studies examining the relationship between prenatal acetaminophen and autism or autism traits in children. Because not all the studies were of the same size or included the same analysis, the included studies differed in their results. In those studies that did show an increase in risk after prenatal acetaminophen administration, none of the relative risk ratios were large enough to be considered a singular “cause”. Other scientists have noted significant methodological concerns with these studies, including that the studies did not properly control for confounding variables, including genetics or the “why” of acetaminophen exposure during pregnancy. For example, women take Tylenol during pregnancy to reduce fever; fever during pregnancy is a known autism risk factor, so the question remains whether any increase in autism diagnosis was due to the fever or the acetaminophen. In fact, in a recent ADHD study, Tylenol was found to be protective against ADHD when pregnant women took it to reduce fever. Fever is a known risk factor for a wide range of neurodevelopmental disorders.
One of the studies included in the systematic review was a study of 2.4 million Swedish children utilizing a sophisticated design that used siblings as a control rather than a completely different group of children with no family history of autism. This design controls for some maternal health factors as well as some genetic influences. Using the sibling control design, any association with autism that was previously seen disappeared. This suggests that genetic and maternal health factors are also critical to any documented association with autism. Those findings were also replicated in a recent study from Japan, which also used a sibling control group to understand the roles of confounding factors like genetics and maternal health on a Tylenol association. Unfortunately, since that study was published just recently, it was not included in the earlier systematic review. If it had been, the conclusions from the systematic review may have been different.
Based on the existing data, there is not sufficient evidence to support a link between acetaminophen and autism. However, as with any medication taken during pregnancy, patients should consult with a trusted medical advisor. The American College of Obstetricians and Gynecologists says acetaminophen is a safe way to treat pain and fever during pregnancy when used in moderation.
Leucovorin and Autism
President Trump and RFK also recommended leucovorin (folinic acid) as a treatment for autism. A small percentage of individuals with autism show low levels of cerebral folate. Scientists have hypothesized that the low folate levels are caused by the presence of antibodies in the blood that block or bind folate and prevent it from getting into the brain. However, non-autistic family members of these autistic individuals also show high levels of folate antibodies, suggesting that the high levels of folate antibodies are not a cause of autism.
Data suggesting that leucovorin may ameliorate some of the symptoms of autism comes from four very small trials, all using different doses and different outcomes, and in one case, reliant on a specific genetic variant. A much higher standard of science would be needed to determine if leucovorin is an effective and safe treatment for autism. This science is still in very early stages, and more studies are necessary before a definitive conclusion can be reached. We welcome additional investigation into leucovorin, but based on existing data, the Autism Science Foundation does not recommend leucovorin as a treatment for autism.
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ASF Media Contact:
C.J. Volpe
cvolpe@autismsciencefoundation.org
