Autism And Acetaminophen: New Evidence From Global Research

In this article, we explore emerging global research examining a possible link between acetaminophen use and autism, and what the latest evidence may mean for parents and clinicians.

🎧 ▶️ Press play below to listen.

🇨🇳 中文（简体）

本文将探讨来自全球的新兴研究，这些研究正在评估对乙酰氨基酚的使用是否与自闭症存在潜在关联，以及这些发现对家长和临床医生意味着什么。

请按下方的播放按钮收听。

🇪🇸 Spanish (Latinoamérica)

En este artículo analizamos nueva evidencia de investigaciones internacionales que examinan una posible relación entre el uso de acetaminofén y el autismo, y lo que estos hallazgos podrían significar para padres y profesionales de la salud.

Presiona el botón de reproducir para escuchar.

Introduction

In September 2025, U.S. President Donald J. Trump sparked international debate when the White House released a fact sheet titled “FACT: Evidence Suggests Link Between Acetaminophen & Autism.” (White House)

The announcement highlighted new research suggesting that the common pain reliever acetaminophen (Tylenol, paracetamol) may increase the risk of autism and ADHD when used during pregnancy.

The reaction was immediate and intense. World health officials, including the World Health Organization, swiftly rejected the claim, calling the evidence “inconsistent” and warning that no definitive causal link has been proven. (NPR). Here are some quotes from the NPR article.

“Available evidence has found no link between the use of paracetamol during pregnancy and autism,” the European Medicines Agency, Europe’s top drug regulator, said in a statement.”

“There were some observational studies that have suggested a possible association between prenatal exposure to acetaminophen, but the evidence remains inconsistent,” he said. “Several studies done after that have found no such relationship. So this lack of replicability calls for caution in drawing causal conclusions about the role of acetaminophen in autism.” – World Health Organization spokesperson Tarik Jašarević

“Don’t pay any attention whatsoever to what Donald Trump says about medicine,” Wes Streeting, the U.K. health secretary, said in an interview with ITV’s Lorraine program. “I’ve just got to be really clear about this: there is no evidence to link the use of paracetamol by pregnant women to autism in their children. None.”

Still, the announcement brought attention to an undeniable reality: diagnoses of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) have risen steadily over the past two decades.

Autism now affects about 1 in 36 children in the U.S., while ADHD diagnoses approach 1 in 10 school-aged children. These increases cannot be ignored, and they raise urgent questions about whether environmental factors—including medications once thought safe—are partly to blame.

This article reviews the September 2025 study that reignited the debate, three earlier studies that support its conclusions, and one large study by Ahlqvist et al. that reached a different result.

By comparing these findings, we can understand why study design matters—and why the question of acetaminophen’s safety in pregnancy is now at the center of global scientific and political discussion.

II. The September 2025 Study (Molecular Sciences Review)

In September 2025, the International Journal of Molecular Sciences published a landmark review that reignited concerns about acetaminophen use during pregnancy. The paper examined how the drug’s toxic metabolite, NAPQI, harms developing fetal cells by targeting the mitochondria—the tiny “power plants” of human cells.

The review describes how NAPQI buildup leads to mitochondrial dysfunction, a process that triggers oxidative stress and widespread cellular injury.

Since mitochondria are critical for brain development, the authors argue that this pathway provides a biologically plausible explanation for why acetaminophen exposure has been repeatedly linked to conditions like autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD).

What makes this study especially significant is that it connects the dots between clinical associations and a clear biological mechanism.

Epidemiological studies have shown statistical associations, but this mechanistic model strengthens the causal argument, making it harder to dismiss the risk as a coincidence or the result of confounding factors .

III. Clinical Studies That Support the Acetaminophen ADHD Autism Link

While the September 2025 review explained how acetaminophen can damage developing brains through mitochondrial toxicity, the following three studies focus on the clinical associations—showing what actually happens in children exposed in the womb.

Each study adds strength by using different methods and large populations, making the findings harder to dismiss.

1. Ji et al. (2021, European Journal of Epidemiology)

This study analyzed cord blood biomarkers of acetaminophen from more than 70,000 mother–child pairs. By measuring actual drug metabolites at birth, it avoided the weaknesses of recall surveys.

The results were striking: children in the highest exposure group were over three times more likely to be diagnosed with ADHD or autism.

This biomarker-based approach gave one of the strongest signals yet of a real, dose-dependent effect.

Why Cord Blood Biomarkers Still Matter

An obvious limitation is that acetaminophen and its metabolites have a short half-life (2–3 hours in adults, somewhat longer in newborns). Therefore, if cord blood is tested at delivery, it primarily reflects recent use in the hours preceding birth.

Readers might then wonder: Does this really tell us how much acetaminophen the mother took during the entire pregnancy?

The answer lies in population-level epidemiology:

• Single measurement vs. cumulative exposure: While a cord blood test does not capture the full history of acetaminophen use, when studied across thousands of pregnancies, it acts as a proxy for maternal behavior. Mothers who took acetaminophen repeatedly or long-term are more likely to have detectable metabolites in cord blood at delivery.
• Biological plausibility: Detecting any acetaminophen metabolite in cord blood confirms that the drug crosses the placenta and directly exposes the fetus. This strengthens the biological argument, especially when combined with mechanistic studies showing mitochondrial toxicity.
• Risk stratification: Ji et al. found a dose-response pattern—higher cord blood acetaminophen levels were linked to greater risks of ADHD and ASD. This suggests that cord biomarkers can still differentiate between “low” and “high” fetal exposures, even if exact timing and dosing remain unknown.

In short, cord blood biomarkers do not precisely indicate how much or how often a mother used acetaminophen. Still, they provide a validated snapshot of in utero exposure that becomes powerful when aggregated in large cohorts.

2. Ricci et al. (2023, Paediatric and Perinatal Epidemiology)

Ricci and colleagues performed one of the largest and most detailed analyses on this subject to date. They compiled data from 23 different cohorts, encompassing more than 367,000 children worldwide.

In these studies, most mothers were asked directly about their acetaminophen use during pregnancy, usually through questionnaires or interviews, and in some cases, researchers also checked medical or pharmacy records.

With such a large dataset, the results were clear: children exposed to acetaminophen in the womb had about a 30–50% higher risk of developing ADHD.

The researchers also found that the risk increased the longer mothers used the drug, showing a dose–response relationship. This is important because it suggests the association is not just random—it strengthens the case that acetaminophen itself plays a role.

Ricci et al. showed that the risk signal doesn’t disappear when you adjust for or remove the medical reasons for taking acetaminophen. That strengthens the case that it’s something about acetaminophen exposure itself — not just the conditions that lead mothers to use it — that may be influencing children’s neurodevelopment.

Later in this article, we’ll compare these findings to the Ahlqvist study, which came to a weaker conclusion. The contrast largely comes down to how exposure was measured. Ricci’s meta-analysis relied on detailed maternal reports across multiple populations, whereas Ahlqvist’s study utilized registry data that often underestimated real-world acetaminophen use.

3. Prada et al. (2025, Environmental Health)

Using the rigorous Navigation Guide methodology, this systematic review assessed 46 studies. It concluded that the majority showed significant associations between acetaminophen use in pregnancy and ADHD or autism.

The authors noted that the highest-quality studies were the most likely to detect risk, strengthening confidence that the link is not due to bias or random chance.

The Navigation Guide Methodology

One of the most important frameworks applied in this field is the Navigation Guide methodology, as used by Prada et al. (2025). This approach is specifically designed for environmental health questions where randomized controlled trials are either unethical or impractical. It works by:

• Systematically reviewing all available observational and mechanistic studies.
• Grading each study for risk of bias, confounding, and exposure/outcome assessment quality.
• Synthesizing evidence transparently to provide a strength-of-evidence rating.

This method helps avoid cherry-picking and allows researchers to weigh the totality of evidence, much like how agencies evaluate environmental toxins. Prada et al. reviewed 46 studies, of which 27 showed significant positive associations, 9 yielded null results, and 4 suggested protective effects.

Importantly, higher-quality studies were more likely to show harm, strengthening the overall conclusion.

By applying the Navigation Guide, the authors concluded there is consistent evidence that prenatal acetaminophen exposure increases the risk of neurodevelopmental disorders, including ADHD and autism. This adds credibility to the clinical associations and complements mechanistic findings.

4. Alemany et al. (2021) – European Meta-analysis

Alemany and colleagues, including Liew, combined data from six large European birth cohorts covering more than 73,000 mother–child pairs. Unlike smaller single-country studies, this project harmonized information across multiple populations to strengthen reliability.

Mothers reported their acetaminophen use during pregnancy through structured questionnaires and interviews at several time points, which gave researchers a clearer picture of exposure than studies relying only on registry notes.

The investigators then tracked children’s development using both parent reports and, in some cohorts, hospital diagnoses of autism and ADHD.

The results showed that prenatal acetaminophen use was linked to a 19% higher risk of autism symptoms and a 21% higher risk of ADHD symptoms.

Significantly, the team carefully adjusted for many other factors—such as maternal smoking, obesity, depression, alcohol use, fever, and infections—and the link still held.

Postnatal use of acetaminophen, by contrast, was not associated with autism or ADHD, pointing specifically to the prenatal period as the window of vulnerability.

This study is especially valuable because it directly addresses a common criticism: that the apparent risk might reflect underlying maternal health conditions.

By showing that the associations persisted even after adjusting for those comorbidities, Alemany et al. added weight to the growing case that acetaminophen itself, not just maternal illness, may play a role in shaping neurodevelopmental risk.

Taken together, these studies paint a consistent picture. Ji et al. showed that acetaminophen itself can be detected in cord blood, directly linking fetal exposure to a higher risk of autism and ADHD.

Prada et al. (2025), using the rigorous Navigation Guide methodology, found that higher-quality studies were more likely to show positive associations, strengthening confidence in the link.

Alemany et al. (2021) added weight by harmonizing data from six European cohorts and demonstrating that the associations persisted even after adjusting for maternal smoking, obesity, and depression.

Ricci et al. (2023), pooling more than 367,000 children, not only confirmed the risk but also revealed a dose–response relationship that could not be explained away by the reasons mothers took acetaminophen, such as fever or pain.

Together, these findings reinforce the consistency of the association across different populations, methods, and levels of analysis.

With this growing body of evidence, it is essential to examine now why one large study—Ahlqvist et al.—arrived at a different conclusion, and what its design limitations may reveal about the challenges of studying this question.

IV. The Outliers

Not all studies have found a strong link between acetaminophen and neurodevelopmental disorders. Two studies discussed below concluded otherwise.

Ahlqvist et al. Population-Based Study

A large Swedish study by Ahlqvist and colleagues analyzed medical registry data from hundreds of thousands of pregnancies.

Instead of asking mothers directly about acetaminophen use, the researchers relied on records collected by midwives at prenatal visits, where women reported all medications they used.

Here’s the problem: acetaminophen is an over-the-counter drug that many women take casually—often without mentioning it during a routine visit. This means a lot of real use was likely missed or underreported in the registry.

As a result, many children who were, in fact, exposed may have been incorrectly counted as “unexposed.” This kind of misclassification tends to weaken the apparent association between exposure and later outcomes.

Ahlqvist’s team also attempted a special “sibling comparison” design, examining families where one child was exposed and another wasn’t. While this method helps control for shared genetics and family background, it shrinks the number of usable cases and reduces statistical power. That made it harder to detect true differences.

Because of these limitations, Ahlqvist et al. found only weak or no links between acetaminophen use and later autism, ADHD, or intellectual disability.

When we place this alongside Ricci’s meta-analysis, the difference in findings makes sense. Ricci’s strength lay in directly asking mothers across multiple cohorts and pooling data from over 367,000 children, whereas Ahlqvist’s reliance on registry records overlooked many real-world applications.

In other words, it’s not that one study disproves the other—the contrast highlights how much study design and exposure measurement matter in shaping the conclusions.

It is interesting, though, that Ahlqvist was the author interviewed by Nature about acetaminophen and autism. Nature referred to the study by Prada et al., which is superior to Ahlqvist’s research in terms of methodology, but they did not interview any of the authors.

Damkier et al. Clinical Perspective Study(2025)

Another outlier comes from a clinical perspective article that reviewed nine original studies and three meta-analyses. Unlike Ricci, Alemany, Ji, or Prada, this paper placed heavy emphasis on the limitations of existing studies.

Why the conclusion differs

1. Selection of studies
   • The authors reviewed 56 relevant publications but only included 9 original studies and 3 meta-analyses that they judged to have the most valid outcome definitions.
   • This means many supportive studies were excluded, potentially biasing toward a conservative conclusion.
2. Focus on confounding
   • The paper emphasizes familial confounding (shared genetics and environment) as a likely explanation for the associations.
   • It highlights that when sibling-comparison designs were used, the associations with acetaminophen weakened substantially.
   • By prioritizing these designs, they interpret the evidence as more consistent with confounding than with causation.
3. Interpretation style
   • Unlike Ricci, Prada, or Alemany, which highlight dose–response patterns and robustness after adjusting for maternal illness, this perspective article stresses the limitations—selection bias, variability in adjustments, and unmeasured confounders.
   • It then concludes that “in utero exposure is unlikely to confer a clinically important increased risk.” That’s a cautious, guideline-oriented stance rather than a dismissal of all associations.

Key difference

• Supportive studies (Ricci, Prada, Alemany, Ji) argue that the signal persists even after adjusting for maternal health and confounding.
• This perspective article gives more weight to sibling designs and potential residual confounding, which dilutes the observed risk and leads them to conclude that the effect is “unlikely clinically important.”

👉 In short, the difference comes from study design emphasis and interpretive lens: they trust sibling-comparison designs more, while others see those as underpowered and prone to misclassification.

V. Why the Results Differ

Study	Exposure Measurement	Sample Size	Outcome Measurement	Main Finding	Strengths & Weaknesses
Ji et al. 2021 (Eur J Epidemiol)	Cord blood biomarkers (objective drug/metabolite levels at birth)	70,000+	Clinical diagnoses (ASD/ADHD)	3× higher risk in highest exposure group	✅ Objective measurement; dose–response ❌ Smaller sample size
Alemany et al. 2021 (Eur J Epidemiol)	Maternal self-report (questionnaires/interviews) across 6 European cohorts	73,000+	Parent-reported symptoms + hospital diagnoses (ASD/ADHD)	19% ↑ autism symptoms; 21% ↑ ADHD symptoms (prenatal use only)	✅ Large harmonized dataset; adjusted for smoking, obesity, depression, alcohol, infections ❌ Reliance on self-report; not as objective as biomarkers
Ricci et al. 2023 (Paediatr Perinat Epidemiol)	Maternal self-report across 23 cohorts	367,000+	ADHD (clinical/behavioral), ASD inconsistent	30–50% ↑ ADHD risk; stronger with longer use	✅ Large dataset, meta-analysis ❌ Self-report exposure prone to bias
Prada et al. 2025 (Environ Health)	Review of 46 studies, weighted by quality	N/A	Multiple NDD outcomes	Consistent associations; strongest in high-quality studies	✅ Navigation Guide method ensures rigor ❌ Still limited by study heterogeneity
Molecular Sciences Review 2025 (Int J Mol Sci)	Mechanistic toxicology, lab & cell data	N/A	Mitochondrial/oxidative stress pathways	NAPQI damages fetal mitochondria → plausible causal link	✅ Explains biological mechanism ❌ Not direct human outcome data
Ahlqvist et al. 2022 (Sweden)	Prescription records only (misses OTC use)	2.5 million+	Registry diagnoses of ASD/ADHD/ID	Weak or null associations	✅ Massive sample size, registry reliability ❌ Major underestimation of exposure, misclassification bias
Damkier et al. 2025, (Obstetrics Gynecology)	Review of selected high-quality studies, emphasis on sibling comparisons	N/A	ADHD/ASD outcomes from prior literature	Concluded in utero exposure “unlikely to confer a clinically important risk”	✅ Highlights confounding, sibling designs ❌ Excludes many supportive studies; underpowered sibling data; interpretive bias toward null

The mixed conclusions across studies don’t necessarily mean the science is contradictory. Instead, they highlight how study design and exposure measurement shape the outcome.

Summary

When acetaminophen exposure is measured carefully—whether through cord blood biomarkers, detailed maternal reports, or systematic reviews pooling high-quality studies—the results consistently show a higher risk of autism and ADHD.

By contrast, the Ahlqvist study relied only on prescription records, missing the vast majority of over-the-counter use. This led to major exposure misclassification, which likely explains its weak or null findings.

In other words, the differences across studies are not due to biology pointing in opposite directions, but rather to study design and exposure accuracy. The better the measurement, the clearer the risk signal becomes.

A Cautionary Tale: Thalidomide

History gives us a painful lesson about rushing to call a medicine safe. In the 1950s, doctors gave pregnant women a sedative called thalidomide to help with morning sickness. It was sold as safe, even harmless. But only a few years later, the world learned the truth — thousands of babies were born with missing or severely shortened arms and legs.

At first, the drug company denied it was the cause. Some doctors also resisted the idea because thalidomide was so widely trusted. But by 1961, the link was undeniable, and the drug was banned. The tragedy left over 10,000 children worldwide with lifelong disabilities.

The thalidomide story shows that even a drug thought to be safe can later be found harmful — especially during pregnancy and child development. This is why scientists and doctors today are taking seriously the growing evidence that acetaminophen use in pregnancy may raise the risk of autism and ADHD.

VI. Conclusion

The debate over acetaminophen use in pregnancy has reached a turning point. For decades, the drug was considered the safest option for fever and pain relief in expectant mothers. But the accumulating evidence from recent years tells a different story.

• The September 2025 review explains how acetaminophen damages developing brains through toxic effects on fetal mitochondria.
• The clinical studies from 2021, 2023, and 2025 show what happens in practice: higher rates of autism and ADHD in exposed children, with dose–response effects and consistency across populations.
• The Ahlqvist study, though large, relied on prescription records that missed most real-world use—its weaker conclusion reflects design limitations rather than proof of safety.

Taken together, the weight of evidence suggests that acetaminophen is not risk-free during pregnancy. The convergence of mechanistic data and large-scale clinical evidence strengthens the argument that prenatal exposure can affect children’s neurodevelopment.

For expectant mothers, the implication is clear: acetaminophen should be used only when truly necessary, and under medical guidance. For policymakers and clinicians, the message is equally urgent: it may be time to reconsider acetaminophen’s long-standing “safe in pregnancy” label.

Like most complex conditions, the cause of autism is almost certainly multifactorial, involving genetic, environmental, and developmental influences.

However, identifying a consistent link between prenatal acetaminophen use and neurodevelopmental risk is an important step. It doesn’t explain the entire rise in autism and ADHD, but it highlights a modifiable factor that could help reduce risk in millions of children worldwide.

History shows that many risks—such as tobacco, lead, and BPA—were dismissed for years until evidence became overwhelming. With acetaminophen, the scientific warning signs are already here. The question now is whether society will act before more children are put at risk.

Don’t Get Sick!

💡 Support This Work

Creating well-researched articles, maintaining this website, and keeping the information free takes time and resources.
If you found this article helpful, please consider donating to support the mission of empowering people to live healthier, longer lives, without relying on medications.

🙏 Every contribution, big or small, truly makes a difference. Thank you for your support!

Follow me on Facebook, Gab, Twitter (formerly known as X), and Telegram.

Related:

1. Children with Post Vaccine Myocarditis have Spike Proteins in their Blood
2. Long COVID syndrome in children and adolescents
3. How Exercise Improves Brain Health in Children with Obesity
4. Mental and Neurologic problems after COVID-19 in children and adults
5. Questions about the COVID-19 Pfizer “vaccine” trial for babies and toddlers
6. The FDA approved Pfizer COVID-19 shots for babies and toddlers, and that is wrong!
7. Fenbendazole Warning: Lethal Liver Toxicity With Acetaminophen
8. Turbo Cancer Fears: Shocking New Data Demands Urgent Answers
9. Deadly Diet: How Ultra-Processed Foods Destroy Your Body And Mind
10. Invisible Killers: The Startling Truth About Microplastics That’s Everywhere
11. Microplastics in breast milk
12. Microplastics found in the Human Placenta, Intestines and Sputum
13. Toxic Metals, Glyphosate Found in Girl Scout Cookies

References:

1. Bandoli, Gretchen, et al. “Acetaminophen Use in Pregnancy: Examining Prevalence, Timing, and Indication of Use in a Prospective Birth Cohort.” Paediatric and Perinatal Epidemiology, vol. 34, no. 3, 2020, pp. 287–296. https://pubmed.ncbi.nlm.nih.gov/31696962/
2. Alemany S, et al. Prenatal and postnatal exposure to acetaminophen in relation to autism spectrum and attention-deficit and hyperactivity symptoms in childhood: Meta-analysis in six European population-based cohorts. Eur J Epidemiol. 2021 Oct;36(10):993-1004. doi: 10.1007/s10654-021-00754-4. Epub 2021 May 28. PMID: 34046850; PMCID: PMC8542535. https://pubmed.ncbi.nlm.nih.gov/34046850/
3. Ricci, Christina, et al. “In Utero Acetaminophen Exposure and Child Neurodevelopmental Outcomes: Systematic Review and Meta-analysis.” Paediatric and Perinatal Epidemiology, vol. 37, no. 5, 2023, pp. 662–677. https://pubmed.ncbi.nlm.nih.gov/36939050/
4. Prada, Diddier, et al. “Evaluation of the Evidence on Acetaminophen Use and Neurodevelopmental Disorders Using the Navigation Guide Methodology.” Environmental Health, vol. 24, no. 1, 2025, p. 34. https://ehjournal.biomedcentral.com/articles/10.1186/s12940-025-01208-0
5. Ahlqvist, Viktoria H., et al. “Acetaminophen Use During Pregnancy and Children’s Risk of Autism, ADHD, and Intellectual Disability.” JAMA Pediatrics, vol. 176, no. 12, 2022, pp. 1227–1235.
6. Santangelo, John F., et al. “Acetaminophen’s Role in Autism and ADHD: A Mitochondrial Perspective.” International Journal of Molecular Sciences, vol. 26, no. 18, 2025, p. 8912.
7. Damkier P, et al. Acetaminophen in Pregnancy and Attention-Deficit and Hyperactivity Disorder and Autism Spectrum Disorder. Obstet Gynecol. 2025 Feb 1;145(2):168-176. doi: 10.1097/AOG.0000000000005802. Epub 2024 Dec 5. PMID: 39637384.
8. Centers for Disease Control and Prevention. “Data and Statistics on Autism Spectrum Disorder.” CDC, 2025.
9. Centers for Disease Control and Prevention. “Data and Statistics on ADHD.” CDC, 2024.
10. Danielson, Melissa L., et al. “ADHD Prevalence among U.S. Children and Adolescents in 2022: Diagnosis, Severity, Co-Occurring Disorders, and Treatment.” Journal of Clinical Child & Adolescent Psychology, 2024.
11. McBride, W. G. “Thalidomide and congenital abnormalities.” The Lancet, 1961.
12. Lenz, W. “Thalidomide and congenital abnormalities.” The Lancet, 1962.
13. Kim, J. H., & Scialli, A. R. “Thalidomide: the tragedy of birth defects and the effective treatment of disease.” Toxicological Sciences, 2011.

© 2018 – 2025 Asclepiades Medicine, LLC. All Rights Reserved
DrJesseSantiano.com does not provide medical advice, diagnosis, or treatment

As an Amazon Associate, I earn from qualifying purchases