Case not closed: One study about Tylenol

[Maxmars]

With apologies to Tylenol fallout, an ongoing discussion about the topic generally.

I thought this might address many subtopics... so...

The Paracetamol Question That Two Million Babies Cannot Quite Answer

(Also ref: https://jamanetwork.com/journals/jamaped...ct/2845519)

In a recent article about a study which summarizes the inquiry thusly:
 

Question  Are maternal prescriptions of acetaminophen during pregnancy associated with offspring’s attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorders (ASDs) in population-based full cohort vs sibling-matched analyses?

Assuming all due diligence, this study is reported to raise several points about the data regarding what they found as measurements of ADHD and autism-type issues in mothers who used any of the acetaminophen product family...

Ultimately... there is a roller-coaster of weirdly contradictory evidence which may or may not be related to what it is we measure (or don't) and how we measure it (or should.) 

Statistics reportedly derived from this research tell us:

The numbers, on the face of it, look damning. Among the 2,092,926 singleton births captured in Taiwan’s National Health Insurance database between 2004 and 2015, just over 48 per cent were born to mothers who had received at least two paracetamol prescriptions during pregnancy. Pei-Chen Lee at National Cheng Kung University and colleagues compared these children to those whose mothers had used it less or not at all, and found a clear association: children in the exposed group were about 12 per cent more likely to be diagnosed with ADHD, with a similar, if somewhat smaller, pattern for autism. Higher doses, or more frequent prescriptions, were associated with higher risk. The classic shape of a dose-response relationship.

The author soberly reminds us that is is not 'causative'... and is only a correlation...

But... if you look at the same data... it shatters expectations when you look at the same data through the filter of "siblings."

In fact... weirdly (as you'll read in the text) it leads to this text...

... Except then the Taiwan team looked more closely at their sibling data, and something strange emerged. They split the sibling pairs by birth order, asking separately: what happens when only the older sibling was exposed, and what happens when only the younger one was? The answers flatly contradicted each other. When the older sibling alone had been exposed in utero, that child was 33 per cent more likely to have ADHD than their unexposed younger sibling, and 75 per cent more likely to be diagnosed with autism. When only the younger sibling had been exposed, the picture reversed completely: that child was actually less likely to have ADHD or autism than their unexposed older sibling. The same drug, the same analytical design, opposite results depending on which child you were looking at.

There is no plausible biological story in which paracetamol protects a younger child’s neurodevelopment while harming an older one. Which means the reversal is not about paracetamol at all.

(Bold is mine)

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