Scientists comment on reports that the Trump Administration will link paracetamol (Tylenol) use to autism in children.
Prof Ian Douglas, Professor of Pharmacoepidemiology at the London School of Hygiene and Tropical Medicine (LSHTM), said:
“Trying to measure whether exposure to paracetamol during pregnancy causes autism or other neurodevelopmental delays is very difficult. Firstly it’s hard to get an accurate measure of whether a woman was actually exposed to paracetamol during pregnancy because it can be difficult to recall everything that’s been taken. But once that’s done to the best of our ability, the next step is to see if the offspring of women who took paracetamol were more likely to be diagnosed with autism or other neurodevelopmental delays, compared with the offspring of women not exposed to paracetamol. Here’s where the second problem with such studies comes in; women who take paracetamol during pregnancy are different from women who don’t for all sorts of reasons. For instance, we have to remember that paracetamol would only be taken for a specific reason, and that many of these underlying reasons could themselves be causes of autism. As an example, paracetamol might be taken because of infection or fever that was severe enough to warrant treatment, or to help manage a long term condition. It’s the job of researchers to account for these differences as best they can, so that if we still see an association, it may indicate a possible cause. This is notoriously difficult to do, because we almost never perfectly measure these differences and many are entirely unmeasured, for example genetics.
“A Swedish study last year attempted to bypass some of these problems by making comparisons between siblings whose mother’s only used paracetamol in one of their pregnancies. This analysis found no increased risk of autism and concluded that past studies which did find an increased risk were likely to be subject to the problems outlined above. The data they used is also of extremely high quality, and unlikely to be improved on elsewhere.
“In short, whilst some studies have found small associations between paracetamol and autism, we should be very wary of jumping to a causal link. More robust ways of studying this question have found no increased risk.”
Prof Claire Anderson, President of the Royal Pharmaceutical Society, said:
“Paracetamol has been used safely by millions of people for decades, including during pregnancy, when taken as directed. It is the first-line choice for pain management and fever control in a variety of patients, including pregnant women, children and the elderly.
“A large study conducted in 2024 found no evidence of a link between paracetamol use in pregnancy and an increased risk of autism in children. This research, which followed over 2.4 million children, provides reassurance for expectant parents that paracetamol remains a safe option for managing pain or fever during pregnancy when used as recommended.
“Anyone with concerns about their medicines should speak to a pharmacist or other trusted healthcare professional to ensure they are getting sound advice from a trusted source.”
Dr Edward Mullins, Clinical Associate Professor at The George Institute for Global Health, Imperial College London, said:
“The best available evidence is that paracetamol use in pregnancy is not linked to autism. In the absence of any new evidence, the reported press release from the Trump administration claiming it is would appear to be an unsubstantiated theory which is likely to lead to an essential treatment for fever and pain being denied to women in pregnancy without good reason, contrary to US and European medical guidance.
“A high-quality review of the evidence in this area looked not only at whether mothers of children with autism took paracetamol (acetaminophen) during pregnancy but crucially also assessed the existence of known risk factors for autism, why paracetamol was taken e.g. a fever or inflammatory arthritis, whether the parents already had diagnoses like autism and whether the child’s siblings had diagnoses like autism (because there is an inheritable element) and concluded, ‘Acetaminophen use during pregnancy was not associated with children’s risk of autism, ADHD, or intellectual disability in sibling control analysis. This suggests that associations observed in other models may have been attributable to familial confounding.’”
Prof Angelica Ronald, Professor of Psychology and Genetics at the University of Surrey, said:
“There is a lot of empirical evidence from many decades of robust research, conducted across a range of countries, that does not support the claim that paracetamol causes autism.
“Twin studies show that in fraternal (also known as dizygotic) twins, if one twin has autism, typically the other twin does not have autism. If paracetamol caused autism, we would see both twins in a pair having autism. However that is not the case, typically one fraternal twin has autism and the other does not.
“Molecular genetic research has uncovered hundreds of genes that cause or influence likelihood of developing autism. There are many forms of autism, some of which are caused by known genetic differences. This evidence is also incompatible with the idea that paracetamol is a major cause of autism.
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“The best evidence to assess whether paracetamol causes autism is a population-based design with a sibling control i.e. https://jamanetwork.com/journals/jama/fullarticle/2817406.
“This sibling control study shows that paracetamol use in mothers is not associated with autism in offspring.”
Dr Linden J Stocker, Consultant in Fetomaternal Medicine, University Hospitals Southampton, said:
“As an experienced consultant in fetomaternal medicine, I have been prescribing paracetamol in pregnancy throughout my career. Paracetamol has been well-studied in pregnancy, and there is no good evidence that it harms the unborn baby. It is also one of the longest-used painkillers we have used in pregnancy, and therefore the data we have on this drug is good.
“Some studies suggest that paracetamol use in pregnancy might be linked to behavioural problems in children, but these studies have unreliable findings. Overall, there is no proof that paracetamol exposure in the womb affects a child’s behaviour. Moreover, paracetamol has been used for many years to help women with pain in pregnancy. Suggesting to pregnant women that this drug is unsafe will cause much anxiety to women who already feel vulnerable and overwhelmed with information. This yet again feeds into the rhetoric that women should be deprived of a well-tested and much needed medication in pregnancy.”
Dr Monique Botha, Associate Professor in Social and Developmental Psychology at Durham University, said:
“There are many studies which refute a link, but the most important was a Swedish study of 2.4 million births (1995–2019) published in 2024 which used actual sibling data and found no relationship between exposure to paracetamol in utero and subsequent autism, ADHD or intellectual disability. This suggests no causal effect of paracetamol in autism. This is further strengthened by there being an absence of a dose dependent relationship. There is no robust evidence or convincing studies to suggest there is any causal relationship and any conclusions being drawn to the contrary are often motivated, under-evidenced, and unsupported by the most robust methods to answering this question. I am exceptionally confident in saying that no relationship exists.
“Similarly, pain relief for pregnant women is woefully lacking and paracetamol is a much safer pain relief option during pregnancy than basically any other alternative and we need to take pain seriously for women including whilst pregnant. The fear mongering will prevent women from accessing the appropriate care during pregnancy. Further, it risks stigmatising families who have autistic children as having brought it on themselves and reinvigorates the long pattern of maternal shame and blame as we’ve seen re-emerge repeatedly over the last 70 years where we try to pay the fault of autism at the mother’s door one way or another.”
On Leucovorin as a treatment
“More evidence is needed with regards to the effect of Leucovorin and core autistic traits before any inferences can be drawn in any meaningful way. Any evidence available at this point is exceptionally tentative and would not be considered to be robust. Similarly whilst medications may help with very specific aspects, there is no medication or treatment that actively cures or erases autism, though it might adjust behaviour, or reduce co-occuring symptoms which contribute towards distress for autistic people. Autism is a lifelong heritable disability whose primary cause is exceedingly likely to be genetic, expressed through a wide array of genes. Similarly, autistic people are exceptionally heterogenous so any treatment or medication for specific traits is likely to work for very specific presentations of autistic traits, in very particular contexts. Sweeping statements about cures or treatments do not tend be accurate, helpful, or ethical.”
Prof Dimitrios Siassakos, Professor in Obstetrics and Gynaecology at University College London and Honorary Consultant in Obstetrics at University College London Hospital, said:
“Autism results from several factors, often combined, particularly genetic predisposition, and sometimes low oxygen at the time of birth as a result of complications. Research has shown that any apparent marginal increase as a result of paracetamol/acetaminophen use in pregnancy tends to disappear when the analyses take into account the factors that matter most. For example, in studies looking at siblings, any association disappeared – it was the family history that mattered and not the use of paracetamol. Undue focus on paracetamol would risk preventing families from using one of the safest medications to use in pregnancy when needed.”
A version of this article was originally posted at Science Media Centre and is reposted here with permission. Any reposting should credit both the GLP and original article. Find Science Media Centre on X @SMC_London
