The U.S. president has just advised that pregnant women and children should avoid using Tylenol (paracetamol) (acetaminophen) except in cases of extreme necessity, after linking its use to the onset of autism spectrum disorders. The announcement comes a day after Trump declared that “we have found an answer to autism” and introduced leucovorin (an analogue of vitamin B9, folic acid) as a solution. In reality, however, the administration lacks conclusive data to support any such recommendation.
- Where does all this come from? From the obsession of Health Secretary Robert Kennedy Jr. with linking a supposed “autism epidemic” to “our food system, our water, our air, different forms of parenting… and to considering vaccines.” On Monday, Kennedy again tied vaccines to autism, invoking an alleged sidelining of those who have sought to investigate such links, including affected families.
Last April, Kennedy announced “a massive effort of testing and research” to determine the cause of autism within five months. The plan promised to distribute $50 million over three years among various research centers chosen by the government. - The data he has now presented: there is no new data. He refers instead to analyses of older studies that were not designed to determine whether Tylenol (paracetamol) itself causes autism. And there is nothing new because, according to CNN, none of the major research centers that applied for funding to investigate the origins of the disorder has confirmed receiving a grant—let alone produced conclusive results so far.
In reality, Trump has consistently spoken about a specific brand, Tylenol, which is how household paracetamol is known in the United States. It has been approved there since 1955 and has shown no serious safety issues in 70 years. - So why paracetamol? Because there was already some suspicion. Some studies “have shown that prenatal exposure to Tylenol (paracetamol) may alter fetal development,” explains Dr. Eduard Gratacós of ICGON-Clínic Barcelona, who drafted a report on the issue in 2021. There appears to be an increased risk of certain mild neurodevelopmental disorders, as well as urogenital and reproductive effects. But it is not clear that paracetamol alone is the cause. And that does not mean paracetamol directly causes autism.
As pediatric neurologist Alfonso Amado, a member of the Neurodevelopment Group of SENEP, told Newtral.es: “There is no evidence that brief therapeutic doses cause specific harm. The greater concern seems to be linked to frequent, prolonged use or high doses, although even this has not been conclusively defined”.
There is no “autism epidemic.” Despite the language used by Kennedy or Trump (“meteoric rise”), the Autism Science Foundation in the U.S. was quick to refute the claim that cases are increasing. What is happening, experts say, is better and broader diagnosis.
Kennedy twisted the conclusions of Centers for Disease Control and Prevention data on the prevalence of autism spectrum disorders, according to Dr. Alycia Halladay of the foundation. “This report is the most compelling evidence that changes in factors such as access to services and the destigmatization of autism spectrum disorder (ASD) are driving the rise in prevalence.” States that devote more resources to autism, she noted, are the ones that report higher prevalence.
Publicidad “There is greater awareness among healthcare and education professionals, allowing for earlier diagnoses and the detection of milder cases that previously would have gone unnoticed,” said Dr. Pedro Viaño of the Spanish Association of Pediatrics (AEP). “In no case is there an epidemic.” That said, he added, there may be environmental factors—diet, pollution, substance abuse—contributing to prevalence, “but this is more controversial and should be approached with caution”.
Political context: Two figures and two key factors behind this announcement
Kennedy Jr. is not only an avowed anti-vaxxer, he is a libertarian anti-pharma throwback steeped in the New Age philosophy of a certain strain of the left from the last third of the 20th century. According to several U.S. medical societies, Tylenol (paracetamol) may be the scapegoat used, first, to attack Tylenol, the most popular brand of this analgesic, until recently produced by Johnson & Johnson; it’s an easy card to play because it isn’t hard to find a mother of a child with autism who has taken paracetamol. And second, as a Trojan horse to encourage the anti-vaccine narrative, even if vaccines aren’t the explicit target this time. This would be a first step.
Trump is an on-again, off-again anti-vaxxer. He has repeatedly shown a penchant for pitching major breakthroughs or cures in simplistic terms, tied to a single cheap product. It happened with hydroxychloroquine during the COVID pandemic. Now his “magic” molecule is leucovorin. In both cases, the evidence is scant or misinterpreted—typical of disinformation or conspiracy forums. He is now giving those circles free rein to continue the narrative linking autism to vaccines, using Tylenol (paracetamol) as the pretext.
Kennedy’s vaccination panel has voted to restrict access to COVID-19 vaccines. At the moment, it remains unclear whether Americans can still go to pharmacies to be immunized. The panel also voted against the (combined) administration of the tetravalent vaccine in children. Meanwhile, the Secretary of Health asked Nature to retract a study demonstrating that components of certain vaccines do not cause illnesses or disorders such as ASD. Nature refused.
Why Tylenol (paracetamol) has not been proven to be “the cause of autism”
- What there are indications of: “Paracetamol is an endocrine disruptor, capable of interfering with the normal activity of hormones.” That does not mean it is an unsafe medicine—quite the opposite. Measuring the scope of possible side effects or previously undescribed adverse outcomes has been a complex task in recent years.
In 2021, an analysis of studies published in the European Journal of Epidemiology did find evidence that children exposed to paracetamol before birth were more likely to develop symptoms of ASD and ADHD—19% and 21% more likely, respectively. Lead author Silvia Alemany stresses she does not want to spark alarm. She recommends that, as with any medication, “patients should consult with the healthcare professionals monitoring their pregnancy.”
The study does not claim to prove that Tylenol (paracetamol) itself causes ASD. Rather, it highlights associations that may warrant attention, as paracetamol could be one of several contributing factors. “It is biologically plausible” that it may play a role in brain development, Alemany noted. But this still requires deeper investigation, and “it is highly unlikely that a single factor could explain why someone receives an ASD diagnosis.”
Co-author Jordi Sunyer, a researcher at ISGlobal, emphasized that “while paracetamol should not be banned for pregnant women or children, it should only be used when necessary”—a point that is not new.
Along the same lines, a robust evidence review published this summer in BMC Environmental Health reached similar conclusions. But as Dr. Pedro Viaño cautioned, “it is a preliminary study compared with the bulk of existing evidence, so it must be treated with caution and in no case does it contraindicate prescribing Tylenol (paracetamol) to pregnant women or children.” That does not mean these studies are poorly conducted, but they may face limitations—as their authors acknowledge—or require further exploration of clinical, genetic, or family-related aspects. For instance, did the expectant mothers take paracetamol because of a serious infection, which is itself a known risk factor for autism? - On balance, the case for paracetamol remains strong. In 2024, an analysis published in JAMA followed 2.4 million births in Sweden. Looking specifically at siblings, the study found that whether mothers took more, less, or no Tylenol (paracetamol) at all made no difference in the emergence of autism spectrum disorders or ADHD.
Well-designed studies linking paracetamol and autism are observational. They show an association but not definitive causation.
A sentence of pain and guilt for women
- Without alarmism: “I am extraordinarily confident that there is no relationship,” said Monique Botha of Durham University in the UK, who recommends paracetamol as the first option. “We must take seriously the pain of pregnant women,” she stressed, noting that they are often blamed and condemned to a narrative of “you shall give birth in pain.” She calls for alarmism to be set aside.
It is estimated that between 46% and 56% of pregnant women in high-income countries use paracetamol, which is considered the safest analgesic and antipyretic during pregnancy and childhood. Dr. Viaño invokes the general principle that applies to almost all medicines: use “the minimum effective dose and appropriate prescription for the symptom”.
“Pain or fever—the conditions for which Tylenol (paracetamol) is indicated—are themselves risk factors during pregnancy. As with many other pharmacological treatments, if healthcare professionals consider its use necessary and safe, pregnant women should not be concerned about taking paracetamol”.
Doctor Silvia Alemany, Vall d’Hebron Institut de Recerca
What we know about the origins of autism spectrum disorders
“Autism is the result of several factors, often combined—most notably genetic predisposition and, in some cases, a lack of oxygen at birth due to complications,” notes Dimitrios Siassakos (UCL) in comments to Spanish SMC. In 80% of cases, there is not a single clue to its origin.
Genetics appear to play the strongest role in autism. One gene in particular (SHANK3) seems highly relevant, as shown in laboratory brain models. But there is no single “autism gene”; rather, a combination of up to a hundred. It is also known that the loss of just a few amino acids in a crucial protein can affect the activity of hundreds of genes and the development of neurons—and this is where autism spectrum disorders can emerge.
There is no cure because there is no disease—so it makes even less sense to speak of a drug that could “remedy” the condition. As for leucovorin, there is only one study, conducted in 40 people, that found signs of improvement. “More evidence is needed before any meaningful conclusions can be drawn. The evidence available at this moment is exceptionally provisional”, said Dr. Botha.
How much are these factors known to weigh in ASD?
There are indeed environmental factors, but how they act is not clear. There are signs that prenatal diet or exposure to pollutants may favor the birth of babies who go on to develop ASD, though they are likely to need a preexisting predisposition.
Could screens or mobile phones play a role? “There is a broad body of evidence linking early exposure during neurodevelopment to a higher likelihood of language, communication, or interaction difficulties.” That is a long way from blaming screens for autism. It is better understood as a warning signal—an indicator: children predisposed to ASD tend to remain in front of screens for longer periods.
Where the old myth linking vaccines to autism comes from
There is no scientific study linking vaccines to the onset of autism. The origin of this myth lies with an English physician, Dr. Andrew Wakefield, whose research was later shown to lack scientific rigor and to have been falsified. The prestigious medical journal The Lancet published Wakefield’s work in 1998 but subsequently retracted the papers and withdrew them from the journal.
The BMJ investigated Wakefield’s study and concluded it was fraudulent. The doctor had altered patient data to fit the results he wanted. Wakefield was stripped of his medical license. “Neither vaccines nor paracetamol have been proven to cause autism,” concludes Dr. Viaño.
This is a human-supervised machine translation of an article originally published in Spanish on Newtral.es
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