Tylenol: The Evidence

The massive meta-analysis from the Icahn School of Medicine at Harvard Mt. Sinai. Forty-six studies were evaluated; far more evidence than any of the single studies cited by the opponents of Trump and RFK, Jr.  Too lengthy to post in its entirety, but here is the lede:

https://ehjournal.biomedcentral.com/articles/10.1186/s12940-025-01208-0

Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology
Diddier Prada, Beate Ritz, Ann Z. Bauer & Andrea A. Baccarelli
Environmental Health volume 24, Article number: 56 (2025) Cite this article

Abstract

Background

Acetaminophen is the most commonly used over-the-counter pain and fever medication taken during pregnancy, with > 50% of pregnant women using acetaminophen worldwide. Numerous well-designed studies have indicated that pregnant mothers exposed to acetaminophen have children diagnosed with neurodevelopmental disorders (NDDs), including autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), at higher rates than children of pregnant mothers who were not exposed to acetaminophen.

Methods

We applied the Navigation Guide methodology to the scientific literature to comprehensively and objectively examine the association between prenatal acetaminophen exposure and NDDs and related symptomology in offspring. We conducted a systematic PubMed search through February 25, 2025, using predefined inclusion criteria and rated studies based on risk of bias and strength of evidence. Due to substantial heterogeneity, we opted for a qualitative synthesis, consistent with the Navigation Guide’s focus on environmental health evidence.

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.

Background

Pregnancy is a critical period—the embryonic and fetal stages are times of rapid and sequential physiological and developmental changes. The developing brain is especially vulnerable to environmental exposures because of incomplete development of the blood–brain barrier and the ongoing growth, differentiation, and pruning of neurons throughout early childhood. The complex and tightly regulated nature of brain development in utero means that even minor or temporary disruptions to the process can have significant and long-lasting effects on the developing brain. Thus, early exposures to chemicals, toxicants, pharmacologic agents, and other exogenous agents can alter normal neurodevelopment and have long-lasting effects, including neurodevelopmental disorders (NDDs) [1].

NDDs describe a category of conditions that result from deviations in normal brain development, resulting in a wide variety of symptoms that may include difficulties in areas such as learning, social and motor skills, attention, cognition, emotions, and behavior. While the causes of NDDs are often rooted in pregnancy[2], these disorders typically manifest and are diagnosed during childhood, when the function of the child’s brain appropriate for a developmental stage can be assessed. NDDs include autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). ASD affects communication and social interaction; ADHD affects attention and behavior, and affected children show hyperactivity and impulsivity. Different NDDs often have shared/overlapping symptomology as well as shared biological pathways or causes, including toxic exposures during critical developmental windows [3] or genetic causes [4]. A range of prenatal and early-life environmental factors—including, but not limited to, medication use—remain under investigation as potential contributors. However, population-level time trends, which may be influenced by improved diagnostic tools and awareness, cannot establish causation for any single exposure, such as acetaminophen, and may raise the risk of ecological fallacy[5]. Therefore, this review, using the Navigation Guide methodology, focuses on individual-level evidence linking prenatal acetaminophen use with neurodevelopmental outcomes.

Acetaminophen (also known as paracetamol) is currently considered the only pain and fever reducer indicated for use during pregnancy because of the risks of miscarriage or birth defects associated with other analgesics in common use [6]. In fact, associations such as the American College of Obstetricians and Gynecology have reassured patients that acetaminophen is safe to take during pregnancy [7]. Thus, acetaminophen has become the first-line medication for fever and pain during pregnancy. It has been estimated that > 60% of women use acetaminophen during pregnancy for headaches and other pain, or fever, with ~ 20% of pregnant women using acetaminophen for > 20 days [8].

Previous systematic reviews and meta-analyses[10,11,12,13,14,15], have examined the association between prenatal acetaminophen exposure and neurodevelopmental disorders (NDDs). Still, the Navigation Guide methodology offers a rigorous, transparent framework designed for observational studies. Thus, here we applied the Navigation Guide to analyze the available scientific literature to comprehensively assess the influence of prenatal use of acetaminophen on the developing brain and specifically to determine whether prenatal use of acetaminophen causes NDDs including ADHD, ASD, and other symptoms consistent with those disorders in children. The Navigation Guide requires systematic rating and review of each identified study for bias, strength of evidence, and study quality. Thus, we believe that applying the Navigation Guide was fitting to systematically and objectively review the literature on prenatal acetaminophen use and the development of NDDs.

Methods

Study selection

We conducted a systematic PubMed search of the literature on February 2–25, 2025, to identify original papers on the relationship between ADHD/ASD/NDDs and prenatal exposure to acetaminophen, including observational studies and meta-analyses. PubMed was selected as the primary database for its comprehensive coverage of biomedical and environmental health literature, aligning with the study’s focus on prenatal acetaminophen exposure and neurodevelopmental disorders. To ensure completeness, supplementary searches were conducted in ISI Web of Science and Google Scholar using identical keyword strategies (e.g., ‘ADHD AND acetaminophen’). These confirmed the inclusion of all relevant studies, with no additional eligible studies identified beyond those captured in PubMed. To guide study selection, we defined the research question using a Population, Exposure, Comparator, Outcome—PECO framework: Population: offspring of pregnant women assessed for neurodevelopmental outcomes; Exposure: prenatal acetaminophen (paracetamol) exposure, measured via maternal self-report, biomarkers, or medical records; Comparator: offspring of pregnant women not exposed to acetaminophen or exposed to alternative analgesics; Outcome: neurodevelopmental disorders, including ADHD, ASD, or related symptoms, diagnosed or assessed in childhood. Eligible studies were original observational studies (e.g., cohort, case–control) published in peer-reviewed journals, focusing on prenatal acetaminophen exposure and NDD outcomes. We excluded studies on postnatal exposures, non-human studies (in vitro or animal) for the primary analysis, and duplicates or non-original research (e.g., reviews, editorials). To avoid duplication of evidence, we excluded studies presenting results from the same cohort or dataset. When multiple articles used the same data, reviewers retained the study with the largest sample size, the most complete reporting of exposure and outcome data, and/or the highest methodological quality, based on the Navigation Guide’s risk-of-bias assessment. This ensured that only the most robust and representative study from each dataset was included. Titles and abstracts retrieved from the PubMed search were independently screened by two authors to assess eligibility based on predefined criteria. Disagreements were resolved through discussion; if unresolved, a third reviewer adjudicated to ensure consensus. A fourth reviewer updated the methodology, verified study selections, and confirmed result accuracy, aligning with the Navigation Guide’s structured evaluation framework.

Acetaminophen and ADHD
We used the search term “ADHD AND acetaminophen.” Using additional search terms, such as “attention-deficit/hyperactivity disorder,” “paracetamol,” or “Tylenol,” did not identify any additional results. A total of 96 papers were identified (the initial PUBMED search yielded 94 papers, and two additional papers were identified when reviewing the PUBMED search[16] and during Google Scholar confirmation[17]. The exclusion of papers not related to ADHD and prenatal acetaminophen exposure yielded 70 relevant papers: 6 in vitro or animal studies, 18 original (20 total with separate analysis of sibling cohorts) non-duplicative studies in humans, 4 meta-analyses, 28 reviews or studies that duplicated or elaborated on previously published original studies in humans, and 14 editorials or comments (Fig. 1, left).

Fig. 1
figure 1
PRISMA Flowchart of Study Selection. This figure illustrates the identification (n = 516), screening, eligibility assessment, and inclusion (n = 46) of studies, with exclusions detailed for in vitro/animal studies (n = 43), meta-analyses (n = 5), reviews (n = 75), and editorials/comments (n = 37), aligning with the Navigation Guide’s systematic approach

Full size image

Acetaminophen and ASD
We used the search term “(autism spectrum disorder OR autism OR ASD) AND acetaminophen.” Using additional search terms, such as “paracetamol” or “Tylenol”, did not return any additional results. The initial search yielded 114 papers. The exclusion of papers not related to ASD and prenatal acetaminophen exposure yielded 63 relevant papers: 13 in vitro or animal studies, 7 original, non-duplicative studies in humans (8 with separate analysis of sibling cohort), 1 meta-analysis, 30 reviews or studies that duplicated or elaborated on previously published original studies in humans, and 12 editorials or comments (Fig. 1, center).

Acetaminophen and other neurodevelopmental deficits/disorders
We used the search term “(neurodevelopment OR neurodevelopmental disorder OR brain development) AND acetaminophen.” Using additional search terms, such as “paracetamol” or “Tylenol,” did not return any additional results. The initial search yielded 308 papers. To avoid overlapping with the other searches, papers related to ADHD or ASD were excluded. Exclusion of papers not related to neurodevelopment and prenatal acetaminophen yielded 69 relevant papers: 24 in vitro or animal studies, 17 original studies in humans (18 with separate analysis of sibling cohort), 17 reviews, and 11 editorials or comments (Fig. 1, right).

Exclusion criteria
After identifying relevant studies with the above search criteria, we excluded studies that presented results from the same data and were published in two different journals with slight differences.

Data extraction and quality assessment
We used standardized Navigation Guide methodology to extract and evaluate data from the identified studies, including publication year, study design, number of cases, number of controls (for case–control studies), total sample size (for cohort studies), population type, country, risk estimates, confidence intervals, and type of NDD. We also indicated if exposure–response relationships were assessed, as well as the method used, and the resulting effect estimates and 95% Confidence Intervals (CIs). After extracting data, papers were evaluated and synthesized to identify patterns, themes, and trends across studies.

Summary of assessments

We used the Navigation Guide methodology to rate studies based on several metrics. The risk of bias within each study was assessed using the GRADE approach to grade study characteristics that can introduce systematic errors in the magnitude or direction of the results. We rated each study for risk of bias, including participant recruitment/selection, blinding during the study, exposure assessment methods, outcome assessment methods, methods to address incomplete data, selective outcome reporting, and conflict of interest. We ranked each study on each parameter: 1 indicated low risk of bias, 2 indicated probably low risk of bias, 3 indicated probably high risk of bias, and 4 indicated high risk of bias. We calculated an average bias score for each study. For the ‘blinding during the study’ domain, observational studies were rated as high risk of bias (score of 4) when knowledge of the outcome could influence exposure reporting. For instance, retrospective studies relying on maternal self-reports of acetaminophen use collected after a child’s neurodevelopmental disorder diagnosis were rated high risk due to potential recall bias. Prospective designs or biomarker-based assessments mitigated this bias in higher-quality studies.

Deviations from scoring—such as inconsistencies in study methodology, incomplete data reporting, or challenges in applying bias criteria—were addressed through a structured process. During the study selection and data extraction phase, studies were triaged by title, abstract, and full text; two reviewers (AB and DP) independently assigned a score for each Navigation Guide category. Any deviations, such as studies with atypical designs or potential biases, were flagged for further evaluation. To handle these deviations, we conducted sensitivity analyses to assess their impact on the overall findings. Specifically, we performed two analyses: (1) excluding the lowest-scoring studies to evaluate their influence on the results, and (2) re-weighting confounding domains to address potential bias over- or underestimation.

Within the Navigation Guide’s risk-of-bias assessment, confounding, including confounding by indication, was systematically evaluated. Studies were rated as higher risk of bias (score of 3 or 4) if they lacked adjustment for key confounders, such as maternal age, chronic illness, socioeconomic status, smoking, alcohol use, or clinical indications for acetaminophen use (e.g., fever or infection). We also assessed whether studies used sensitivity analyses, negative control exposures, or propensity score matching to address confounding by indication, incorporating these evaluations into the overall risk-of-bias score for each study.

The Navigation Guide may also have additional limitations, including its numeric risk-of-bias scale. By assigning equal weight to every domain, the score can imply unwarranted precision and may fail to distinguish studies with minor shortcomings from those with major threats, particularly when confounding and exposure misclassification bias effects in opposite directions. For instance, in our analysis, confounding and exposure misclassification could bias results in opposing directions, yet the equal weighting of domains may not adequately distinguish studies with minor methodological flaws from those with significant threats to validity. In addition, there is still no consensus on the optimal set of domains for human observational research, nor on how to rate analytical choices (e.g., modelling strategy) as a separate source of bias. To partially address this concern, we conducted sensitivity analyses, including removing the lowest-scoring studies and re-weighting confounding domains twofold, facilitating the interpretation of scores. Finally, the Navigation Guide’s default classification of observational evidence as “moderate” quality may skew final certainty ratings, particularly when integrating diverse study designs. To mitigate these limitations, we employed a triangulation framework, integrating findings from multiple study types to strengthen causal inference.

Following recommendations on causal inference in environmental epidemiology[18], we set our findings within a triangulation framework: when distinct study designs that suffer different, ideally opposing, biases reach congruent results, causal inference is strengthened. Our analysis integrates (i) prospective cohorts susceptible to residual confounding but strong temporality, (ii) biomarker-based studies with low recall bias but possible misclassification of dose, and (iii) experimental models largely free of confounding yet limited in external validity. The convergence of these independent sources of evidence increases confidence that the observed associations are not artefactual.

While a meta-analysis could provide quantitative synthesis, we opted against it due to significant heterogeneity in exposure assessment, outcome measures, and confounder adjustments across the studies evaluated. This variability, combined with non-comparable effect estimates, risked biased pooled results. Instead, the Navigation Guide methodology’s qualitative synthesis, supported by risk-of-bias scoring and evidence triangulation, was deemed more suitable for evaluating the association between prenatal acetaminophen exposure and NDDs.

Go to: https://ehjournal.biomedcentral.com/articles/10.1186/s12940-025-01208-0

for the remainder of this huge study.  We have reached the storage limits of this MHFF site.

Mentally ill, pregnant women are now chugging bottles of Tylenol on TikTok to spite Trump and RFK,Jr.:

https://www.dailymail.co.uk/news/article-15126539/pregnant-liberal-moms-taking-tylenol-tiktok-donald-trump.html

Pregnant Women Reject Trump Advice

Pregnant liberals film themselves downing Tylenol to spite Trump despite autism warning

By Laura Parnaby | 24 September 2025

Pregnant women are filming themselves taking Tylenol in defiance against Donald Trump's shaky claim the painkiller causes autism in children.

The president announced that doctors in the US will begin advising expectant mothers against taking the drug because of an apparent link.

Trump, 79, claimed that taking Tylenol 'is no good', adding that pregnant women should 'fight like hell' to avoid taking it, except for in cases of extreme fever.

Several moms have gone viral on TikTok for posting videos of themselves taking Tylenol in protest.

'Here's me, a PREGNANT woman, taking TYLENOL because I believe in science and not someone who has no medical background,' one mom called Grace wrote over a video of herself taking the pill and dancing.

'Quit believing everything you see and hear,' she wrote in the caption for the video, which racked up almost 30,000 likes and 305,000 views in just 17 hours.

Several studies have linked Acetaminophen, the active ingredient in Tylenol, to higher rates of autism and attention deficit hyperactivity disorder (ADHD).

However, the findings have not often been consistent and many doctors say it is completely safe, and even recommended, because high fevers during pregnancy can harm the mother and child.

'Here's me, a PREGNANT woman, taking TYLENOL because I believe in science and not someone who has no medical background,' one mom called Grace wrote over a video of herself taking the pill, as shown in a screenshot from her TikTok video above

Health Secretary RFK Jr said the advice against using Tylenol is part of a new strategy aimed at 'informing doctors and families about potential risks'.

'We will follow the science, restore trust, and deliver hope to millions of American families,' he said in a statement released by the White House.

Calley Means, an advisor to RFK Jr, shared several videos of moms taking part in the Tylenol video trend on X with the comment: 'No words'.

'Democrats are now chugging bottles of Tylenol on TikTok,' Means wrote as he shared his exasperation to his social media following.

Another mom-to-be named Natalie wrote on TikTok: 'About to take Tylenol for my headache while pregnant, because I don't take my medical advice from a man who doesn't have a degree in science, healthcare, or medicine, and who had a parasitic brain infection.

'Yeah, I'll trust my doctors, who have a degree.'

The trend has also spread beyond America, as mothers overseas are also filming themselves taking the common painkiller in an act of protest against Trump's order.

Pregnant 36-year-old Amy, who lives in the UK, posted a comedic video showing herself acting out punching her husband in the face when he attempted to stop her taking paracetamol, which is what the drug is called in the UK.

Amy said she is 36 weeks pregnant with her second baby, and that her six year old son is autistic.

'I do not believe for one second that Tylenol causes autism, these claims have been debunked before and Trump has given no scientific evidence to back up his claims,' she told the Daily Mail.

'I am from the UK and our NHS guidance still stands that Tylenol/ Paracetamol is the safest form of pain medication during pregnancy.'

Liberal moms have taken to TikTok to film themselves taking Tylenol in defiance against Donald Trump 's unproven claim that it could cause autism in children

Speaking about the Trump administration, she added: 'These are the same people that claim vaccines also cause autism.

'The doctor that made these claims had his license revoked and claims debunked. Autism is genetic, not a single cause.'

Pain management specialist Dr Randa Jaafar said she supports the TikTok trend.

'People listen to TikTok now more than anyone - more than they listen to experts,' she told the Daily Mail.

'I have patients that come in and say "I saw it on TikTok and I want it".

'I think think it's good because I think it will drive the idea home of, don't be scared, don't be guilty if you take Tylenol.'

Jaafar said she thinks the Trump administration is fearmongering and 'causing more harm' to mothers by encouraging them not to take the painkiller.

She said that suffering with fevers and resulting mental distress is worse for fetuses than taking Tylenol could be.

Tylenol's 2017 Advice To Pregnant Women:

https://x.com/tylenol/status/839196906702127106

TYLENOL®
@tylenol

We actually don't recommend using any of our products while pregnant. Thank you for taking the time to voice your concerns today.

2:31 PM · Mar 7, 2017

It turns out that Johnson & Johnson was very concerned about the link between Tylenol and autism during the last decade.  This might have been a driving force for Johnson & Johnson's 2023 spinoff of the Tylenol product line into a new entity called Kenvue.  Might they have been expecting an avalanche of product liability lawsuits?

https://dailycaller.com/2025/09/26/scoop-internal-docs-tylenol-maker-janssen-autism-risk/

SCOOP: Tylenol Maker Privately Admitted Evidence Was Getting ‘Heavy’ For Autism Risk In 2018
By Emily Kopp - September 26, 2025

The pharmaceutical company behind Tylenol privately acknowledged the likelihood of an association between its drug in pregnancy and neurodevelopmental disorders like autism in children seven years ago, company documents obtained by the Daily Caller News Foundation show.

“The weight of the evidence is starting to feel heavy to me,” said Rachel Weinstein, U.S. director of epidemiology for Janssen, the pharmaceutical arm of Johnson & Johnson, in 2018. Johnson & Johnson marketed Tylenol at the time but in 2023 spun off its consumer products division into a separate company called Kenvue.

Legacy media headlines and vocal public health experts have dismissed the conclusion of President Donald Trump and Health and Human Services (HHS) Secretary Robert F. Kennedy Jr. that Tylenol taken in pregnancy and early infancy has driven rises in autism. But one stakeholder has for years viewed the evidence as credible enough to act upon, at least privately: The makers of Tylenol. (RELATED: Trump Unveils Results Of Autism Study)

The DCNF obtained the company documents from the law firm Keller Postman LLC, which brought a class action lawsuit against Kenvue in the Federal District Court for the Southern District of New York.

To be sure, much of the highly-cited research on autism spectrum disorder emphasizes genetic rather than environmental drivers. The scientific community continues to debate its causes, with many scientists agreeing that multiple factors may be at play.

The company’s FAQ webpage says that “acetaminophen is an active ingredient in all TYLENOL® products and in more than 600 other over-the-counter (OTC) and prescription medicines.”

A decade before Weinstein’s email, in 2008, Johnson & Johnson began receiving queries from consumers and physicians about a possible link, emails show.

“Not much choice but to consider this a safety signal that needs to be evaluated,” J&J Office of Consumer Medical Safety Lead Andre Mann wrote in 2008 after receiving a letter from a physician with concerns.

Leslie Shur, the head of the division of Johnson & Johnson that monitors the side effects of drugs already on the market, received an alert in 2012 about concerns about acetaminophen and autism from a concerned father, with one employee writing “in case this goes to press.”

Concerns about a link between Tylenol and neurological disorders may have reached the C-suite by 2014, according to another email, which references then-Johnson & Johnson CEO Alex Gorski.

The makers of Tylenol have closely tracked a drumbeat of scientific publications finding an association between taking the blockbuster drug in pregnancy and infancy and autism risk, other company documents show. (RELATED: Pregnant Influencers Seemingly Try To Own Trump With Tylenol)

A 2018 internal presentation the company labeled “privileged and confidential” acknowledges that observational studies show a “somewhat consistent” association between prenatal exposure to Tylenol and neurodevelopmental disorders. Another presentation slide acknowledges that larger meta-analyses — reviews summarizing multiple scientific studies — found an association, but notes weaknesses of these studies like confounding variables and subjectivity in measuring autistic traits.

“Johnson & Johnson divested its consumer health business years ago, and all rights and liabilities associated with the sale of its over-the-counter products, including Tylenol (acetaminophen), are owned by Kenvue,” a Johnson & Johnson spokesman said in a statement.

Shur did not respond to a request for comment. Mann and Gorski could not be reached for comment.

“Nothing is more important to us than the health and safety of the people who use our products,” Kenvue spokesperson Melissa Witt told the DCNF. “We have continuously evaluated the science and continue to believe there is no causal link between acetaminophen use during pregnancy and autism.”

“Acetaminophen is the safest pain reliever option for pregnant women as needed throughout their entire pregnancy,” Witt continued. “Our products are safe and effective when used as directed on the product label. We recommend pregnant women do not take any over-the-counter medication, including acetaminophen, without talking to their doctor first.”

Hearings before the Court of Appeals for the Second Circuit in the class action suit against Kenvue will begin Oct. 9. Judge Denise Cote granted summary judgement for Kenvue in September 2023, after tossing the scientific testimony from experts for Keller Postman, citing the “great public health implications” of pregnant women not having the drug.

Ashley Keller, lead attorney for the families with autistic children, argues the judge overstepped and that women should be alerted to the risk.

“We saw this nonsense with COVID on all sorts of things that turned out to be untrue. They said these lies were noble lies. Well, we shouldn’t sugar coat things for pregnant moms,” he said to the DCNF.

The judge also responded to the internal records showing that the company knew about studies showing an autism risk by saying that “candid internal discussion […] is positive corporate behavior.”

Meanwhile, Kenvue states on the website for Tylenol that “credible, independent scientific data continues to show no proven link between taking acetaminophen and autism.”

“If you are treating your little one with acetaminophen, please know that there is no credible science that shows taking acetaminophen causes autism,” the site also reads.

Internal emails sharply contrast with that public statement.

Emails show employees of Johnson & Johnson discussing a 2018 literature review concluding that pregnant women should be cautioned against indiscriminate use of Tylenol as well as a 2016 study that concluded that prenatal exposure to acetaminophen was associated with autism “with hyperkinetic features,” or abnormal involuntary movement, though not with autism without those symptoms.

Weinstein, the company epidemiologist, wrote to one of the authors lauding the “substantial strengths of the study design,” the “strength and robustness of the association,” and the study’s ability “to control for possible confounding by indication,” that “lend support to the findings.” Weinstein joined Kenvue from Johnson & Johnson but has since retired, her LinkedIn shows. She could not be reached for comment.

In 2018, Weinstein and other top scientists within the company considered funding follow-on studies about the drug’s autism risk but eventually opted against “sticking their necks out.” Weinstein mentioned that they could end up confirming the findings. The company noted in a 2018 presentation that recommending against Tylenol in pregnancy would leave women with few options.

Tylenol has few competitors among pregnant women, with ibuprofen and aspirin discouraged in late pregnancy due to potential complications.

The company also conducted research it described as “social listening” by tracking Google searches and social media posts seeking evidence about Tylenol and autism from January 2020 through October 2023. The company initiated the social media trends research after the 2021 publication of a call to action on Tylenol in Nature Reviews Endocrinology by 13 U.S. and European experts “in light of the serious consequences of inaction.”

That same year, the company ran a Mother’s Day ad featuring pregnant women and women with small infants and the Tylenol brand. Nevertheless, the company found “a substantial increase in negative sentiment on this topic in the news and social media,” the social listening report states.

Acknowledging a plausible risk to babies could have tarnished the Tylenol brand, employees admitted internally. In a 2023 internal review dubbed Project Cocoon, company executives acknowledged that the question “touches every aspect of the brand.”

The company had in 2015 launched Tylenol as a “megabrand,” marketing it as vital for all stages of life, including in pregnancy and early infancy, internal marketing plans show.

Just two years before, a 2013 ProPublica investigation had uncovered the company had also been slow to update its label with information about the risk of overdose. Tylenol caused 1,500 overdose deaths from 2001 through 2010, more than every other over-the-counter painkiller combined, according to the report. That same year, Tylenol added a message to the bottle caps of its extra strength formulation: “CONTAINS ACETAMINOPHEN” and “ALWAYS READ THE LABEL.”

The renewed push to tie the Tylenol brand to themes of family and safety followed.

“Come back,” one marketing slide reads, showing a picture of a mother and baby.

The class action suit centers on whether the company was negligent in ignoring a credible connection. According to William Parker, CEO of WPLab, Inc. and a neuroscientist formerly associated with Duke University, the hypothesis was first presented in 2008, with strong animal model studies showing its toxicity by 2014.

At the same time, some studies made what Parker describes as a statistical mistake: controlling for factors like genetic predisposition that exacerbate the effects of Tylenol as confounding variables.

“It’s like saying kids playing with matches are perfectly safe when there’s not anything flammable around,” Parker said.

However by 2017, a peer reviewed paper coauthored by Parker connected the genetic and environmental variables with acetaminophen, bringing the probable association between acetaminophen and autism into clearer focus, he said.

All those mentally ill, pregnant women chugging Tylenol should perhaps read the actual science, not the anti-Trump political science.