Paracetamol/Tylenol/Acetaminophen is one of the causes of Autism
- classicrecords1
- 2 days ago
- 5 min read
The latest “review” in the Lancet looking at 43 studies is just an opinion piece and is flawed as it relies far too much on sibling studies.
A 2025 review by scientists from Harvard, Mount Sinai and other major institutions published in BMC Environmental Health that examined 46 previous studies and found that most studies — especially the high-quality studies – showed an association between prenatal acetaminophen use and ADHD, autism and other neurological disorders is also an opinion piece.
Which “opinion piece” do you believe?
Knee-jerk opposition to the warning-label update for Tylenol is not warranted, given that there is evidence in the scientific literature providing cause for concern about possible negative neurodevelopmental effects of Tylenol.
For example:
Ji et al., “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 (2020): https://pubmed.ncbi.nlm.nih.gov/31664451/
Conclusions and relevance: Cord biomarkers of fetal exposure to acetaminophen were associated with significantly increased risk of childhood ADHD and ASD in a dose-response fashion. Our findings support previous studies regarding the association between prenatal and perinatal acetaminophen exposure and childhood neurodevelopmental risk and warrant additional investigations.
Bauer et al., “Paracetamol use during pregnancy - a call for precautionary action”, Nat Rev Endocrinol (2021): https://pubmed.ncbi.nlm.nih.gov/34556849/
We recommend that pregnant women should be cautioned at the beginning of pregnancy to: forego [acetaminophen] unless its use is medically indicated; consult with a physician or pharmacist if they are uncertain whether use is indicated and before using on a long-term basis; and minimize exposure by using the lowest effective dose for the shortest possible time.
Most recently, in August 2025, the Dean of Harvard’s School of Public Health co-authored a review paper in the journal BMC Environmental Health with the following strong conclusion (from the Abstract): https://ehjournal.biomedcentral.com/articles/10.1186/s12940-025-01208-0
Results
We identified 46 studies for inclusion in our analysis. Of these, 27 studies reported positive associations (significant links to NDDs), 9 showed null associations (no significant link), and 4 indicated negative associations (protective effects). Higher-quality studies were more likely to show positive associations. Overall, the majority of the studies reported positive associations of prenatal acetaminophen use with ADHD, ASD, or NDDs in offspring, with risk-of-bias and strength-of-evidence ratings informing the overall synthesis.
Conclusions
Our analyses using the Navigation Guide thus support evidence consistent with an association between acetaminophen exposure during pregnancy and increased incidence of NDDs. Appropriate and immediate steps should be taken to advise pregnant women to limit acetaminophen consumption to protect their offspring’s neurodevelopment.
There are some interesting hypotheses about the possible role of acetaminophen in the “autism epidemic”.
In a 2009 article “Did Acetaminophen Provoke the Autism Epidemic?”, Peter Good explained that Tylenol began to be used as the primary anti-fever medication for infants and young children in the 1980s, following a US Centers for Disease Control and Prevention (CDC) report that aspirin was associated with a rare brain and liver condition (Reye’s syndrome) associated with recovery from certain childhood diseases like chickenpox. https://pubmed.ncbi.nlm.nih.gov/20030462/
The 1980s was also the decade in which autism rates began to increase significantly in the USA.
As Good explains in his review, whereas many authors have proposed that the increased administration of the Measles, Mumps and Rubella (MMR) vaccine to infants beginning in 1978 may be responsible for the increased incidence of autism starting in the 1980s, Schulz et al. (2008) had proposed acetaminophen as an alternative hypothesis, since Tylenol is the main drug used as a treatment for fever and pain following the administration of vaccines in infants and children.
In the same vein, President Trump is reported to have made statements in his press conference yesterday “discouraging Tylenol for both pregnant women and newborns after vaccination”.
The White House listed some studies with a possible link here ……
Regarding the ethics of testing Schulz et al.’s hypothesis, Good notes:
[C]an it be ethical to administer acetaminophen to a child whose ability to detoxify acetaminophen may be critically impaired? One alternative: when parents become sufficiently wary of giving acetaminophen to infants and young children, the same kind of “natural study” may occur as when acetaminophen replaced aspirin in the 1980s.[Ref 9] When enough parents stop giving (and taking) acetaminophen, and give aspirin or another remedy instead, any effect on the incidence of autism may be apparent within several years.
Yesterday’s presidential announcement could influence a substantial number of American women to consider avoiding Tylenol during pregnancy and refraining from allowing it to be given to their infants and young children, which could in turn produce the data needed to better understand whether acetaminophen does or does not have an important effect on autism incidence in the USA.
Regarding parents’ and doctors’ “fear of fever” in infants and young children, thoughtful medical advice from such prominent voices such as the late pediatrician Dr. Robert Mendelsohn strongly advocate against too-prevalent pharmaceutical intervention and for allowing the natural healing process to take its course, at least beyond the critical first period of up to approximately three months after birth:
https://pathwaystofamilywellness.org/childrens-health-wellness/eliminate-the-fear-not-the-fever.html.
Several major studies published in top journals examining the link between Tylenol and autism or attention-deficit/hyperactivity disorder (ADHD) have found an association, although some have found none.
No studies have identified a definitive causal link, and most call for more research.
Studies that have suggested a link include:
A 2019 Johns Hopkins Bloomberg School of Public Health study published in JAMA Psychiatry that analyzed data from the Boston Birth Cohort, a 20-year study of early life factors influencing pregnancy and child development. The researchers found that exposure to acetaminophen in the womb may increase a child’s risk for ADHD or autism. They concluded, “Appropriate and immediate steps should be taken to advise pregnant women to limit acetaminophen consumption to protect their offspring’s neurodevelopment.”
A 2019 observational study published in the American Journal of Epidemiology that analyzed data on nearly 9,000 children born between 1993-2005 to women enrolled in the Nurses’ Health Study II cohort. The researchers found a link between prenatal acetaminophen use and ADHD.
A 2021 consensus statement that was based on a comprehensive review of experimental and epidemiological literature published between 1995-2020 in the PubMed scientific database. The authors noted that acetaminophen is an endocrine disruptor that can cross the blood-brain barrier and that they found evidence that it may alter neurodevelopment.
Based on the links evident in their review, they concluded that the “harm from continued inaction exceeds the harm that might arise from precautionary action,” and called for further research.
Some children can’t effectively metabolize acetaminophen
Not all studies have had the same findings. A population-based observational study in Sweden published in 2024 in the Journal of the American Medical Association found no link between use of acetaminophen and autism, ADHD or intellectual disability.
However, Tylenol researcher William Parker, Ph.D., disagrees with the conclusions from the Swedish study. He said the study actually shows that acetaminophen is linked to autism only when combined with other key risk factors.
In 2024, Parker and colleagues published a study in Clinical and Experimental Pediatrics that identified links between acetaminophen and autism when used prenatally and also when used during early life in susceptible babies and children.
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