Autism Research Updates: What We Know About Acetaminophen and Leucovorin

On Monday, September 22nd, 2025, the Trump administration shared updates regarding research into the causes of autism and potential treatments. “We announce historic steps to confront the crisis of autism. Horrible, horrible crisis,” President Trump declared. These updates come a few months after the US Health and Human Services Secretary, Robert F. Kennedy, announced that they expected to have answers to the "autism epidemic" by September.

The announcement included claims about acetaminophen use during pregnancy, vaccine timing and composition, and the potential role of leucovorin (folinic acid) as a treatment option for autism. It also highlighted new research initiatives aimed at further exploring environmental and genetic contributors to autism. Let's take a closer look.

Important Note: I acknowledge that this topic can be sensitive in today's politically charged climate. The intention of this article is not to endorse or oppose any political figure or government agenda. Autism is not—or at least should not—be political. Instead, my goal is to clarify what was announced, separate fact from misinformation, and provide ABA providers with evidence-based context to better understand current events and support the families they serve.

Minimizing the Use of Acetaminophen (Tylenol) During Pregnancy

The primary announcement focused on acetaminophen use during pregnancy. President Trump announced, “Effective immediately, the FDA will be notifying physicians that the use of acetaminophen—which is commonly known as Tylenol—during pregnancy can be associated with a very increased risk of autism.” He added, “With Tylenol, don’t take it. There's no downside to not taking it." Many experts are cautioning against this generalized recommendation.

What does it mean: The FDA is urging against the routine use of acetaminophen during pregnancy except in extreme cases. A new warning label on acetaminophen products will be required, citing a possible association between autism and its use.

While the President was firm in his stance, stating, "Fight like hell not to take it," the FDA Commissioner and the head of the NIH acknowledged the complex and nuanced nature of these recommendations. They encourage clinicians to exercise clinical judgment when considering whether to recommend a patient take Tylenol while pregnant. If it's deemed necessary, they should advise the lowest dosage for the shortest duration of time necessary.

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What Does the Research Say?

Observational studies have reported associations between frequent use of Tylenol during pregnancy and neurodevelopmental differences in children. In other words, correlation exists. However, no causal relationship between acetaminophen and autism has been established. Correlation is not the same as causation. Research has suggested that associations observed are likely due to confounding variables.

For example, a study published in JAMA Psychiatry in 2019 found that higher concentrations of acetaminophen in blood samples taken at birth were linked to a higher risk of autism and ADHD. In contrast, a large-scale study published in 2024 found no significant increased risk of autism in mothers who used acetaminophen—1.42% of children exposed to acetaminophen during pregnancy were autistic, compared to 1.33% of children who were not exposed.

Even in studies that reported an elevated risk, the relative risk ratios weren't strong enough to support acetaminophen as a direct cause (Autism Science Foundation, 2025).

It appears the justification for the new guidance on acetaminophen was based on a qualitative synthesis published in August 2025 that found associations between acetaminophen and autism. However, the authors recognize several limitations and emphasize that these results indicate correlation, not causation. Recommendations offered in the article were also less alarmist, with authors stating, "We recommend judicious acetaminophen use—lowest effective dose, shortest duration—under medical guidance, tailored to individual risk–benefit assessments, rather than a broad limitation." This differs drastically from the President's emphatic insistence to avoid acetaminophen.

Does this mean Tylenol doesn't cause autism? Well, not necessarily. We should use caution to avoid speaking in absolutes. The absence of evidence isn't the same as evidence of absence. However, the existing body of research has failed to establish a causal relationship, pointing to a high likelihood that correlation is more likely a result of confounding variables.

Should Moms Discontinue Tylenol Use While Pregnant?

Deciding to use any medication while pregnant requires a discussion between the expecting mother and their medical provider. It's worth highlighting that the following organizations have reaffirmed their recommendation advising that acetaminophen is an appropriate medication to treat pain and fevers during pregnancy.

American College of Obstetrics and Gynecology stated, "More than two decades of research have found no causal link between acetaminophen use during pregnancy and autism, ADHD, or intellectual disability in children. Acetaminophen continues to be an important and safe option for managing pain and fever in pregnancy—conditions that can pose serious risks to pregnant patients and their fetuses if left untreated."

The Society for Maternal-Fetal Medicine stated, "Despite assertions to the contrary, a thorough review of existing research suggesting a potential link between acetaminophen use during pregnancy and an increased risk of autism and attention deficit and hyperactivity disorder (ADHD) in children has not established a causal relationship."

The American Psychiatric Association stated, "Autism is a complex disorder, and it is incorrect to imply that a handful of studies have established causation. A strong base of evidence shows that acetaminophen, when taken as directed, is safe for use during pregnancy. Any decisions around a course of treatment should be determined by a patient and their doctor."

What's the harm in telling expecting mothers not to take Tylenol?

While suggesting fewer medications during pregnancy might seem harmless, broad statements from leaders or agencies that the public relies on for evidence-based guidance can have unintended consequences. Roughly 62% of expecting mothers take acetaminophen (Bandoli et al., 2020). Oftentimes, mothers are taking it as a last resort due to debilitating migraines, toothaches, infections, fevers, and other ailments. Strong statements like "Fight like hell not to take it" may create undue pressure on mothers to avoid taking a medication that can offer relief from pain and fever.

Untreated fevers during pregnancy can pose serious risks to the developing baby. Public health guidance should be based on evidence, not opinions or unfounded claims. As the Chief Science Officer of Autism Science Foundation explained, "This claim risks undermining public health while also misleading families who deserve clear, factual information." This highlights the need for improved transparency about the evidence behind sweeping recommendations.

Kaelynn Partlow, an autistic advocate, explained it well in a recent video, sharing, "Science needs strong, repeated, controlled studies before you can announce anything as fact. Those studies haven't occurred yet. When leaders toss out half-baked claims, it's the autism community who pays the price."

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Vaccines and Autism

Another area President Trump addressed in Monday's announcement was the administration of vaccines in babies and young children. He reopened past claims about the potential link between vaccines and autism. This is another area of autism etiology that has been well-studied. Researchers have failed to connect vaccinations to autism.

Trump began his discussion focused on the hepatitis B vaccination, stating, “Hepatitis B is sexually transmitted. There’s no reason to give a baby that’s almost just born hepatitis B. So I would say wait until the baby is 12 years old and formed, and take Hepatitis B.”

While it's true that hepatitis B, a viral infection that attacks the liver, can be transmitted through sexual contact, that's not the only route of transmission. It's also not accurate to say there's no reason to give a baby this immunization. The virus can be passed from a mother to her infant during childbirth due to exposure to infected blood or even from close household contact. The CDC has recommended a universal hepatitis B vaccine in newborns since 1991. This early protection has been shown to be highly effective in reducing infection rates (American Academy of Pediatrics, 2025).

Research shows that the younger an individual is when they contract Hepatitis B, the worse the consequences are. Those who are infected in their first year of life have a 90% chance of developing chronic hepatitis B. Of these, 25% will die from the disease. Delaying the vaccine until age 12, as Trump suggested, would leave infants and children vulnerable to a serious and preventable disease.

Last week, at a vaccine advisory meeting, the Advisory Committee on Immunization Practices (ACIP) intended to vote on changes to the timing of the hepatitis B vaccine, but ultimately tabled the vote. They did vote to alter recommendations on the combined measles, mumps, rubella, and varicella vaccine for children under four due to an increased risk of febrile seizures when the varicella vaccination is combined with the MMR. That vote doesn't change the recommendation for children to be vaccinated against MMR and varicella (chicken pox). It's important to note that large epidemiological studies have found no link between the MMR vaccine and autism.

Leucovorin as a Potential Treatment for Autism

The other primary announcement made on Monday was regarding a new potential treatment option for autism. Leucovorin, a form of folinic acid, a B vitamin, is used to counteract the side effects of chemotherapy drugs. It is also sometimes used off-label to treat vitamin B9 deficiency (Mayo Clinic, 2025). A few small studies have indicated the potential to improve some symptoms in children with autism. With this, the FDA is relabeling leucovorin as an autism treatment.

Some individuals with autism have low levels of cerebral folate. Researchers have suggested that low folate levels could be caused by antibodies in the blood that block or bind folate, preventing it from reaching the brain. In children for whom this is the case, leucovorin may help alleviate some symptoms. However, research into this area is in the very early stages, making it too soon for the scientific community to provide a definitive conclusion regarding its safety and effectiveness.

Should families seek a prescription for leucovorin? Again, the decision to take a medication should be made collaboratively between the family and the child's pediatrician. For autistic children diagnosed with cerebral folate deficiency, families may wish to discuss leucovorin as a potential option with a trusted medical professional.

Will leucovorin be covered by insurance? The CMS reports Medicaid will cover leucovorin prescriptions. They anticipate private payors following suit.

How can ABA professionals help? Medication recommendations are outside the scope of practice and competency of a BCBA. However, if a family opts to try leucovorin for their child, ABA professionals can support them with data collection and analysis to help them make informed decisions about the continued use of this medication. For example, clinicians can utilize event lines in their behavior and skill acquisition graphs that communicate when the child began leucovorin.

Increased Funding for Autism Research

Lastly, the administration announced increased funding for autism research. The NIH is dedicating $50 million to 13 research projects known as the Autism Data Science Initiative. The focus of each of these studies is on identifying root causes and treatments for autism.

What Causes Autism?

Over decades of autism research, it has become clear that autism does not have a single cause. Autism is a complex neurodevelopmental condition and is believed to be a combination of multiple genetic and environmental factors. In about 15-20% of autistic individuals, a specific genetic cause can be pinpointed. In other cases, autism occurs as a result of gene mutations. In addition to the genetic causes, there are potential genetic and environmental interactions that influence the risk of autism.

Environmental influences that could potentially increase the risk of autism include:

• Advanced parental age

• Prenatal exposure to air pollution or pesticides

• Maternal obesity, diabetes, or immune conditions

• Extreme prematurity or very low birth weight

• Birth complications leading to periods of oxygen deprivation to the baby’s brain (National Institute of Environmental Health Sciences, nd).

While certain environmental and social determinants appear to increase the risk of autism, an increased risk isn't the same as a cause. Most people who are exposed to certain environmental risk factors don't develop autism.

Main Takeaways

The September 2025 announcement brings to light the complexities of autism spectrum disorder. There is no single cause, and decades of research have yet to establish a causal link between autism and acetaminophen use during pregnancy or vaccines. While increased awareness and greater funding are positive signs, it's essential that public health officials rely on evidence-based guidance to support families with accurate information and avoid sharing misinformation or misinterpretations of research, thereby preventing unnecessary fear and inadvertent consequences.

We encourage behavior analytic professionals to exercise philosophical doubt when evaluating research or interpretations of research, especially when the findings concern vulnerable populations.

References

Ahlqvist, V. H., Sjöqvist, H., Dalman, C., Magnusson, C., Gardner, R. M., & Rai, D. (2024). Acetaminophen use during pregnancy and children’s risk of autism, ADHD, and intellectual disability. JAMA, 331(14), 1205–1214. https://doi.org/10.1001/jama.2024.3172

American Academy of Pediatrics. (2025). Fact checked: Hepatitis B vaccine given to newborns reduces risk of chronic infection. https://www.aap.org/en/news-room/fact-checked/fact-checked-hepatitis-b-vaccine-given-to-newborns-reduces-risk-of-chronic-infection/

American Psychological Association. (2025, September). Psychologists advocate for autism amid a wave of misinformation. Monitor on Psychology. https://www.apa.org/monitor/2025/09/advocate-autism-wave-misinformation

Autism Science Foundation. (2025, September 22). Autism Science Foundation statement on White House announcement on autism. https://autismsciencefoundation.org/press_releases/asf-statement-wh-briefing/

Autism Science Foundation. (n.d.). Causes, signs and symptoms. Autism Science Foundation. Retrieved September 23, 2025, from https://autismsciencefoundation.org/causes-signs-and-symptoms/

Bandoli, G., Palmsten, K., & Chambers, C. (2020). Acetaminophen use in pregnancy: Examining prevalence, timing, and indication of use in a prospective birth cohort. Paediatric and perinatal epidemiology, 34(3), 237–246. https://doi.org/10.1111/ppe.12595

Mayo Clinic. (2025, February 1). Leucovorin (oral route, intravenous route, injection route) – description. Retrieved from https://www.mayoclinic.org/drugs-supplements/leucovorin-oral-route-intravenous-route-injection-route/description/drg-20064503 

National Institute of Environmental Health Sciences. (n.d.). Autism. National Institutes of Health. Retrieved September 23, 2025, from https://www.niehs.nih.gov/health/topics/conditions/autism

Ji, Y., Azuine, R. E., Zhang, Y., Hou, W., Hong, X., Wang, G., Riley, A., Pearson, C., Zuckerman, B., & Wang, X. (2020). Association of cord plasma biomarkers of in utero acetaminophen exposure with risk of attention-deficit/hyperactivity disorder and autism spectrum disorder in childhood. JAMA Psychiatry, 77(2), 180–189. https://doi.org/10.1001/jamapsychiatry.2019.3259

U.S. Food and Drug Administration. (2025, September 22). FDA responds to evidence of possible association between autism and acetaminophen use during pregnancy. https://www.fda.gov/news-events/press-announcements/fda-responds-evidence-possible-association-between-autism-and-acetaminophen-use-during-pregnancy