Why Ecological Studies Mislead: The 2013 Circumcision Analysis

You requested; we delivered. Lots of Science Fictions listeners have asked us to take a look into Donald Trump and RFK, Jr.’s recent claims about Tylenol (that is, paracetamol or acetaminophen—all the same thing). Does it cause autism?

It turns out there’s more to this than you might’ve thought—regardless of all the recent hype, a lot of very reputable scientists take the idea seriously. But should they? In this emergency podcast, we go through all the relevant studies.

The Science Fictions podcast is brought to you by Works in Progress magazine. In the ad this week we mentioned “The Death Rays that Guard Life”, an article from Issue 20 of the magazine about far-UVC light and how—with a lot more research—it might be the next big thing for reducing the spread of germs in hospitals and classrooms. Find that and many other articles and podcasts at worksinprogress.co.

Show notes

* The FDA’s September 2025 announcement on Tylenol and autism

* The UK’s Department of Health and Social Care announcement the same day

* “The phrase ‘no evidence’ is a read flag for bad science communication”, by Scott Alexander

* 2003 theoretical paper with speculation about paracetamol and neurodevelopmental disorders

* 2013 sibling control study in the International Journal of Epidemiology

* “Ecological” study in Environmental Health from 2013 about circumcision rates, paracetamol, and autism

* 2015 Danish seven-year follow-up study

* 2019 cord blood study in JAMA Psychiatry

* 2021 “consensus statement” on paracetamol and neurodevelopment

* 2025 Japanese sibling-control study

* 2024 very large Swedish sibling-control study

* Study that sparked the current debate: the “Navigation Guide” review from Environmental Health

* Description of what “Navigation Guide” is

* STAT News on the evidence for a paracetamol-autism link; and on the controversy about the Dean of the Harvard School of Public Health

* White House statement defending the existence of the link

* BMJ article summing up the controversy

Credits

The Science Fictions podcast is produced by Julian Mayers at Yada Yada Productions.

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