A large new study found no evidence that taking acetaminophen, such as Tylenol, during pregnancy increases a child’s risk of autism or ADHD once researchers account for shared family factors that can distort the results of traditional observational research.
A new study reaffirms that taking Tylenol during pregnancy as directed is not linked to neurodevelopmental disorders such as ADHD or autism.
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According to JAMA Internal Medicine, researchers examined health records from an initial group of 708,020 mother-child pairs in Hong Kong, then compared siblings from the same families whose prenatal acetaminophen exposure differed. The sibling analysis included 124,333 children assessed for autism spectrum disorder and 97,285 assessed for ADHD. Researchers found essentially no difference in risk, reporting an adjusted hazard ratio of 1.00 for autism and 1.01 for ADHD. The findings also stayed consistent when researchers looked at when the medication was used, how frequently it was used, and cumulative dose.
The new findings are significant because the Tylenol autism claim has persisted despite a major problem with much of the research behind it: association does not establish causation. In the same JAMA Internal Medicine study, a conventional analysis initially appeared to show higher rates of autism and ADHD among children whose mothers received acetaminophen during pregnancy. But that association disappeared when siblings within the same family were compared. Researchers also found similar statistical associations when mothers used acetaminophen before pregnancy, which the study authors said points toward underlying family, genetic, health, or environmental factors rather than a direct medication effect on fetal development.
The Tylenol autism claim did not begin with one fabricated study or one viral social media post. It developed gradually from legitimate but limited observational research. A 2013 Norwegian study published in the International Journal of Epidemiology via PubMed reported developmental and behavioral differences among some children whose mothers reported prolonged paracetamol use during pregnancy, particularly use lasting more than 28 days. The researchers themselves were studying an association and did not establish that the medication directly caused those outcomes.
Public concern grew further in 2014 after researchers studying 64,322 children in the Danish National Birth Cohort reported an association between prenatal acetaminophen exposure and ADHD related outcomes. According to the study published in JAMA Pediatrics via PubMed, children whose mothers reported acetaminophen use during pregnancy were more likely in the observational data to receive ADHD medication, a diagnosis of hyperkinetic disorder, or show ADHD like behavior. That research helped establish the scientific question that eventually evolved into the broader Tylenol autism claim, but the study could not eliminate every possible explanation for the association.
Other observational studies followed. Some reported modest associations involving behavior, ADHD symptoms, or autism, while researchers continued debating whether the medication itself was responsible or whether factors connected to why pregnant patients take acetaminophen were affecting the results. According to a 2025 practice advisory from the American College of Obstetricians and Gynecologists, recurring problems in this research included reliance on self-reported medication use, incomplete information about dose and duration, inconsistent measurements of childhood development, and inadequate control for genetic and family factors.
The Tylenol autism claim received another major boost in September 2021 when a group of scientists and clinicians published a precautionary consensus statement in Nature Reviews Endocrinology. The authors argued that pregnant patients should avoid unnecessary acetaminophen use, speak with a doctor or pharmacist about prolonged use, and use the lowest effective dose for the shortest necessary period. The paper cited epidemiological and experimental research suggesting possible developmental effects and was ultimately supported by 91 scientists, clinicians, and public health professionals. Importantly, it raised concern and called for precaution rather than proving that acetaminophen causes autism or ADHD.
That same year, other experts published a response in Nature Reviews Endocrinology warning against drawing causal conclusions from the available data. They argued that the existing studies were vulnerable to confounding and other methodological problems, illustrating how divided interpretation of the evidence helped the Tylenol autism claim spread beyond the much narrower conclusions scientists could actually support.
The controversy soon moved into courtrooms. According to the U.S. District Court for the Southern District of New York, federal lawsuits alleging that prenatal acetaminophen exposure caused autism or ADHD were consolidated into multidistrict litigation in October 2022. A district judge later excluded several plaintiffs’ causation experts, but the Second Circuit revived hundreds of claims in July 2026 after ruling that some expert testimony had been improperly excluded. That appellate ruling dealt with whether expert evidence could be presented in court. It did not determine that acetaminophen causes autism or ADHD.
The debate became even more visible in September 2025. The Food and Drug Administration announced that it was beginning a label change process to reflect evidence suggesting a possible association between acetaminophen use during pregnancy and neurological conditions including autism and ADHD. The agency described the evidence as an association rather than proof of causation. Around the same time, Donald Trump publicly urged pregnant women to avoid Tylenol, putting the Tylenol autism claim into an even larger national spotlight.
Other medical organizations reached different conclusions about what the evidence justified. The World Health Organization said in September 2025 that there was no conclusive scientific evidence confirming a link between acetaminophen during pregnancy and autism. The American College of Obstetricians and Gynecologists also maintained its clinical recommendation, stating, “ACOG reaffirms that acetaminophen remains the analgesic and antipyretic of choice during pregnancy.” ACOG recommends appropriate use at the lowest effective dose for the shortest necessary period in consultation with an obstetric care professional.
Another major piece of evidence came from Sweden in 2024. According to JAMA, researchers studied nearly 2.5 million children born between 1995 and 2019. Traditional statistical models showed small associations between prenatal acetaminophen exposure and autism, ADHD, and intellectual disability. However, once researchers compared siblings who shared many genetic and environmental factors, the associations disappeared. The sibling analysis found hazard ratios of 0.98 for autism, 0.98 for ADHD, and 1.01 for intellectual disability, providing another example of how the Tylenol autism claim can look different when family-level confounding is more carefully controlled.
A 2025 umbrella review in The BMJ reached a similar conclusion after evaluating nine previous reviews covering 40 studies. Although many of those reviews had reported positive associations, the BMJ researchers rated confidence in their findings as low or critically low and found that the increased risks did not persist in the strongest sibling-controlled studies. The review concluded that existing evidence does not clearly link maternal acetaminophen use with autism or ADHD.
The latest Hong Kong research adds another large population to that evidence. The authors of the 2026 JAMA Internal Medicine study acknowledged limitations, including the fact that their prescription records did not capture every over-the-counter acetaminophen purchase. Still, the researchers found no meaningful association with autism or ADHD across trimester, usage pattern, or dose and said their findings provide reassurance about acetaminophen when it is clinically indicated during pregnancy. The Society for Maternal Fetal Medicine separately reaffirmed in June 2026 that acetaminophen remains its recommended first-line medication for treating pain and fever during pregnancy.
The history matters because the Tylenol autism claim did not come from nowhere, but it also did not emerge from research proving that Tylenol causes autism. It grew from observational associations that were difficult to separate from genetics, maternal health, reasons for taking the medication, and shared family circumstances. As researchers have increasingly used sibling comparisons and other methods designed to address those problems, the apparent connection has repeatedly weakened or disappeared, including in the newest large-scale study published in 2026.
