A recent announcement from the White House has brought renewed attention to the use of acetaminophen (Tylenol) during pregnancy and its possible connection to autism spectrum disorders (ASD). In this MedCram episode, Dr. Roger Seheult—a board-certified physician in internal medicine, pulmonary disease, and critical care—breaks down the latest findings and biological mechanisms at play.
Acetaminophen: How It’s Metabolized
Tylenol is a widely used over-the-counter medication, often hidden in other drug formulations. It’s metabolized mainly in the liver through two non-toxic pathways:
- Glucuronidation
- Sulfation
However, 5–9% of acetaminophen gets converted into a toxic compound called NAPQI, which causes oxidative stress in the body. Normally, this compound is neutralized by glutathione, a powerful antioxidant. But if glutathione levels are low—due to overdose, illness, or chronic oxidative stress—NAPQI can build up and damage cells.
Why This Matters for Pregnancy & Autism
There’s growing evidence suggesting that oxidative stress and mitochondrial dysfunction are central in the development of neurodevelopmental disorders, including autism. These are some possible biological plausibilities of a connection:
- Chronic or even low-dose Tylenol use during pregnancy could deplete glutathione.
- This could impair fetal brain development, especially during critical periods.
- The fetal brain is highly sensitive to oxidative stress, which could disrupt normal development.
What the Research Shows
A 2025 systematic review using the Navigation Guide methodology analyzed 46 studies on prenatal acetaminophen exposure and neurodevelopmental outcomes like ASD and ADHD:
- 27 of the studies showed a positive association—i.e., higher Tylenol use correlated with higher autism/ADHD risk.
- While causation can’t be confirmed, the review found enough evidence to recommend caution: lowest dose, shortest duration, and only under medical guidance.
The suspected mechanisms?
- Oxidative stress
- Endocrine disruption
- Epigenetic changes
Sunlight, Melatonin, and Antioxidants
Here’s where the discussion gets even more interesting. Dr. Seheult highlights how infrared sunlight plays a surprising but vital role in human health:
- Sunlight exposure, especially near-infrared light, boosts mitochondrial production of melatonin—a more potent antioxidant than glutathione.
- Less sunlight exposure = less melatonin = more oxidative stress.
Fascinatingly, pregnant women naturally become more transparent to infrared light later in pregnancy, possibly allowing sunlight to influence fetal development directly.
Recent studies show:
- Sunlight can pass through the human body, improving mitochondrial function.
- Infrared light exposure increases ATP production, lowers blood glucose, and reduces oxidative stress.
The Modern Problem: Light Deprivation
In modern societies, several trends are reducing our exposure to natural sunlight:
- More time spent indoors
- Widespread use of LED lights, which emit no infrared light
- Low-E glass in buildings blocks beneficial wavelengths
- A new Department of Energy ruling (set for 2028) may further restrict the sale of bulbs with any infrared component due to energy efficiency requirements.
Could all of this be contributing to worsening oxidative stress, especially during pregnancy?
Other Supporting Evidence
- Season of birth matters: Studies show increased autism risk in babies conceived during winter (less sun), and lowest in those conceived during summer.
- Geography matters: Autism rates are lower near the equator and higher at higher latitudes, correlating with less sunlight.
- Somali immigrants in Minnesota showed a dramatic increase in autism diagnoses compared to Somalia—potentially tied to the loss of sunlight exposure.
Should We Rethink Tylenol for Fevers?
While Tylenol is often used to reduce fevers, Dr. Seheult notes:
- Treating moderate fevers (101–102°F) may not always be necessary.
- Fevers help boost immune responses, including interferon, a key antiviral molecule.
- Overuse of antipyretics like Tylenol during infections has been linked to longer illness durations in some studies.
Final Thoughts
Dr. Seheult urges further research—and action:
“There is ample evidence to investigate this more deeply. The balance of antioxidants and oxidative stress may be key—not just for autism, but for chronic diseases in general.”
He also calls on policymakers to re-evaluate light regulations, especially those that may reduce our already limited access to beneficial infrared light.
LINKS / REFERENCES:
Evaluation of the evidence on acetaminophen use and neurodevelopmental disorders using the Navigation Guide methodology (BMC) | https://ehjournal.biomedcentral.com/a…
Melatonin and the Optics of the Human Body (ResearchGate) | https://www.researchgate.net/publicat…
Longer wavelengths in sunlight pass through the human body and have a systemic impact which improves vision (Nature) | https://www.nature.com/articles/s4159…
Going Nowhere Faster: Did the Covid-19 Pandemic Accelerate the Trend Toward Staying Home? (JAPA) | https://www.tandfonline.com/doi/full/…
Birth seasonality and risk of autism spectrum disorder (Springer) | https://pmc.ncbi.nlm.nih.gov/articles…
Autism prevalence in the United States with respect to solar UV-B doses (Dermatoendocrinol) | https://pmc.ncbi.nlm.nih.gov/articles…
A review of prevalence studies of Autism Spectrum Disorder by latitude and solar irradiance impact (Medical Hypotheses) | https://www.sciencedirect.com/science…
Research finds 1 in 16 Somali children diagnosed with autism, 3 times more than state average (MPR News) | https://www.mprnews.org/episode/2024/…
New Department of Energy Rule That Will Change Your Light Bulbs (MedCram) | 
• New Department of Energy Rule That Will Ch…
Treat a Fever? Flu and COVID Update (MedCram) | • Treat a Fever? Flu and COVID Update