Tylenol, pregnancy, and autism: What recent studies show and how to interpret the data

Peter Attia

Oct 6, 2025

Episode description

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In this special episode of The Drive, Peter addresses the recent headlines linking acetaminophen (Tylenol) use during pregnancy to autism in exposed children. Recognizing the confusion these claims have sparked among patients, listeners, and the broader public, Peter uses this episode to provide a framework for thinking critically about complex conditions and the research related to them. He highlights the dramatic rise in autism diagnoses over recent decades, noting that multifactorial conditions rarely have a single cause, and emphasizes the importance of resisting oversimplified explanations. Peter also stresses that humans are not naturally wired for scientific thinking, making disciplined frameworks like the Bradford Hill criteria essential for evaluating causality in epidemiology. Ultimately, he uses this framework to explore the evidence surrounding acetaminophen use during pregnancy and its potential link to autism.

We discuss:

Laying the groundwork for this discussion, the rise in autism rates, and the value in using frameworks [1:00];
The FDA pregnancy drug categories, where Tylenol falls within that framework, and a structured method for evaluating scientific evidence and causality [6:00];
What exactly are the claims being made about acetaminophen and autism? [13:45];
The increase in autism rates and why so many things are being linked to autism: the multiple comparisons problem [15:00];
Evaluating the review paper that triggered the recent concern over acetaminophen and autism [21:45];
Breaking down the largest studies on prenatal Tylenol exposure and autism: is there a causal link? [35:00];
Why observational studies can’t prove causality, the role of confounding variables, and the importance of frameworks like the Bradford Hill criteria [43:30];
Applying the Bradford Hill criteria: testing the case for Tylenol and autism [45:45];
Putting it all together to answer the question: Does acetaminophen use during pregnancy increase the risk of autism? [56:15];
If autism risk is overwhelmingly genetic, what explains the dramatic rise in autism diagnoses? [59:15];
Other risk factors for autism: parent

Episode description

View the Show Notes Page for This Episode

Become a Member to Receive Exclusive Content

We discuss:

Laying the groundwork for this discussion, the rise in autism rates, and the value in using frameworks [1:00];
The FDA pregnancy drug categories, where Tylenol falls within that framework, and a structured method for evaluating scientific evidence and causality [6:00];
What exactly are the claims being made about acetaminophen and autism? [13:45];
The increase in autism rates and why so many things are being linked to autism: the multiple comparisons problem [15:00];
Evaluating the review paper that triggered the recent concern over acetaminophen and autism [21:45];
Breaking down the largest studies on prenatal Tylenol exposure and autism: is there a causal link? [35:00];
Why observational studies can’t prove causality, the role of confounding variables, and the importance of frameworks like the Bradford Hill criteria [43:30];
Applying the Bradford Hill criteria: testing the case for Tylenol and autism [45:45];
Putting it all together to answer the question: Does acetaminophen use during pregnancy increase the risk of autism? [56:15];
If autism risk is overwhelmingly genetic, what explains the dramatic rise in autism diagnoses? [59:15];
Other risk factors for autism: parent

Mindsip insights from this episode:

Manage fever to reduce risks of birth defects and autism

The risk of not taking Tylenol for a fever can be greater, as maternal fever itself is a significant risk factor for birth defects and is associated with up to a 200% increased risk of autism.

#autism

#risk

Debunk Tylenol-autism link through sibling studies

Two massive cohort studies found the Tylenol-autism association was completely abolished when comparing siblings, suggesting the link is due to shared genetics and environment, not the drug itself.

#autism

#genetics

Understand multiple comparisons problem to clarify autism associations

The 'multiple comparisons problem' explains why so many variables are linked to autism; if you test enough variables, you are statistically bound to find associations by pure chance.

#autism

#research

Understand FDA drug risk categories for pregnancy safety

The FDA historically used a letter system (A, B, C, D, X) to classify a drug's risk during pregnancy, where Tylenol is Category B, generally considered safe with caution.

#risk

Recognize genetic factors driving autism risk

Genetics account for an estimated 80-90% of the variability in autism risk between individuals, a concept known as heritability.

#autism

#genetics

Apply Bradford Hill criteria to assess causality in associations

The Bradford Hill criteria provide a disciplined framework of nine principles to help determine if an observed statistical association is likely to be causal.

#research

Understand factors behind rising autism diagnoses

The five-fold increase in autism diagnoses is largely explained by expanded diagnostic criteria (accounting for 40-60% of the increase) and greater public awareness (20-30%).

#autism

Peter Attia

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