What Studies Link Tylenol to Autism and ADHD?

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Acetaminophen is the active ingredient in more than 600 medications. These medications are available by prescription and over the counter. It’s easy to get acetaminophen and take it without consultation with a medical practitioner.

For years, we assumed that Tylenol was safe, even during pregnancy. Although studies began to emerge warning of potential problems with use during pregnancy, these studies were given little attention. Now, the manufacturers of these drugs are being investigated for potential links between Tylenol and acetaminophen to autism and ADHD.

With autism increasing significantly as a diagnosis among young children, scientists are grasping to find causes and contributing factors. One factor that may increase the odds of autism and ADHD in a child is maternal acetaminophen use during pregnancy. (Cleveland Clinic, Pregnancy: Does Acetaminophen Heighten Risk?)

Consensus Statement Warning of Acetaminophen Use in Pregnancy and Autism, ADHD

In 2021, 91 medical professionals signed a Consensus Statement published by Nature Reviews Endocrinology. The statement warned about Tylenol use during pregnancy. The Consensus Statement, titled Paracetamol use during pregnancy — a call for precautionary action, summarized dozens of studies linking Tylenol use to neurological abnormalities, including autism and ADHD.

List of studies linking Tylenol to autism and ADHD.

Studies linking Tylenol to adverse neurological outcomes cover subjects including:

  • Reproduction epidemiology
  • Reproduction experimentation, typically using rats and mice
  • Neurodevelopment epidemiology cohort studies
  • Neurotoxicity experimental studies
  • Reviews – umbrella reviews and meta-analysis

These dozens of studies focus on varying effects using different methodologies. The summation of these studies is sufficient that the signing medical professionals felt confident in recommending precautionary action because of potential harm from Tylenol use during pregnancy.

Findings of Tylenol Studies and Autism – Systematic Review of 16 Studies

In addition to the Consensus Statement, another leading publication warning of the link between acetaminophen in pregnancy use and autism is A Systematic Review of the Link Between Autism Spectrum Disorder and Acetaminophen: A Mystery to Resolve (Khan, Kabinaj, et. all). Published in July 2022, the paper reviews other publications and studies surrounding acetaminophen use during pregnancy.

The paper is a published review of 16 studies. Each study correlates acetaminophen use and neurodevelopmental outcomes. The study concludes that increased caution is needed regarding acetaminophen use during pregnancy. In addition, the review acknowledges known information that acetaminophen use can contribute to other health changes, including asthma.

Summary of the Khan/Kabinaj review paper:

  • A review of 16 published studies suggests a link between acetaminophen use in pregnancy and adverse neurological conditions, including autism and ADHD
  • More prolonged use indicates a stronger association with negative neurological outcomes
  • More substantial doses and higher frequency indicate an increasing correlation with negative neurological conditions
  • Autism is one possible negative outcome along with impaired cognition, ADHD, and an increased risk of asthma
  • Adverse effects may be more prevalent in boys, except that ADHD appears equally in both genders
  • Use of acetaminophen in pregnancy may also contribute to small size and low birth rates for infants

Researchers say the summation of these 16 studies suggests an association between use during pregnancy and negative neurological outcomes. The conclusion of the researchers is that it is “urgent” to conduct further research on this topic.

Understanding Pregnancy and Autism/ADHD Acetaminophen Studies

Medical professionals are struggling to synthesize the data showing a link between autism, ADHD and Tylenol use during pregnancy. While many studies suggest a potential link, scientists are still struggling to explain the connection.

For years, acetaminophen, commonly sold as Tylenol, has been widely available and presumed safe. It is widely used including among pregnant women. Scientists believe that acetaminophen blocks prostaglandin. The drug regulates the part of the brain that controls temperature and responds to pain. It raises the body’s overall tolerance levels for pain.

Scientists admit that there is still a lot they don’t know about how acetaminophen works. Scientists believe that just as acetaminophen may impact the brain in positive ways to relieve short-term pain, it may also negatively impact neurological function when used during pregnancy. Professionals will continue to study how the drug functions with attention to the increasingly apparent link between its use among pregnant women and autism.

Protecting Children – Studies as the Basis of Litigation

As the potential link between Tylenol use in pregnancy and autism/ADHD in children becomes increasingly clear, some parents are using these studies to spur litigation against manufacturers and retailers. The scientific evidence is consolidated, and a consensus has formed among many medical professionals – the risk appears real, and caution is advised.

These studies agree that there appears to be a link between acetaminophen use in pregnancy and negative neurological outcomes. Thousands of children and their families may rely on these studies to pursue a class action lawsuit against acetaminophen manufacturers.

Additional studies:

Kwok, Hall, et al. l, The association between analgesic drug use in pregnancy and neurodevelopmental disorders: protocol for an umbrella review, 2020.

Bauer, Kriebel, et. all, Prenatal paracetamol exposure and child neurodevelopment: A review, 2018.

Ji, Azuine, et. all, Association of Cord Plasma Biomarkers of In Utero Acetaminophen Exposure With Risk of Attention-Deficit/Hyperactivity Disorder and Autism Spectrum Disorder in Childhood, 2020.

Craig, Savino, A systematic review of comorbidity between cerebral palsy, autism spectrum disorders and Attention Deficit Hyperactivity Disorder, 2019

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