Prenatal Paracetamol Usage as a Proxy Marker for ADHD Susceptibility in Children?

Is Paracetamol (APAP) Usage During Pregnancy a Cause of ADHD – Or Just a Proxy Marker For ADHD Susceptibility?

Rethinking a Recent Nature Study Linking APAP to Neurodevelopmental Risk

A recent study published in Nature Mental Health (June 2025) has reignited debate about whether acetaminophen (paracetamol or APAP) taken during pregnancy could contribute to the development of attention deficit hyperactivity disorder (ADHD) in children. Using maternal blood biomarkers rather than self-reported medication use, the researchers reported that prenatal APAP exposure was associated with a more than threefold increase in ADHD diagnosis rates in offspring.

The study also found that children of mothers who had detectable APAP levels during the second trimester showed altered placental gene expression — notably, upregulation of immune system genes and downregulation of oxidative phosphorylation pathways. These changes were especially prominent in female offspring and were linked to increased expression of IGHG1, an immunoglobulin gene associated with immune response.

The paper concludes that these molecular changes may reveal a causal mechanism linking APAP use and developmental neurotoxicity.

But is the APAP medication itself the culprit — or could it be reflecting a deeper correlation?

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🔄 Rethinking the Causal Chain: A Biological Hypothesis

An alternative and biologically plausible explanation challenges the assumption of causation.

Rather than paracetamol directly causing placental gene expression changes or ADHD, APAP use may instead be a marker — a proxy — for something upstream:

• Maternal immune system activation, such as in response to fever, viral infections (like Epstein–Barr Virus), or inflammation.

• Genetic or epigenetic predispositions shared between mother and child, especially those related to ADHD and immune hypersensitivity.

In this view, APAP is not the driver of neurodevelopmental change — it’s the signpost of an activated or dysregulated immune system, which itself is the true underlying risk factor.

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🧬 Why This Matters: ADHD Is Highly Heritable

ADHD is known to be strongly genetic, with heritability estimates around 70–80%. Environmental factors — including maternal stress, immune activation, or infection during pregnancy — can modulate gene expression through epigenetic mechanisms. But the shared biology between mother and child, including neuroimmune traits, cannot be ignored.

If mothers with ADHD traits are:

• More likely to experience immune hypersensitivity,

• More likely to get fevers or inflammatory symptoms during pregnancy,

• More likely to use paracetamol to manage those symptoms,

...then their children may also inherit those immune–neurological sensitivities, increasing their risk for ADHD — independent of APAP exposure.

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🔬 The Role of Maternal Immune Activation (MIA)

Decades of research into maternal immune activation (MIA) shows that infections and immune dysregulation during pregnancy can disrupt fetal brain development. Elevated cytokine levels, inflammation, and placental stress are all known to affect early neurodevelopment. This includes risks for ADHD, autism spectrum disorder (ASD), and other neurodivergent traits.

In fact, some of the same pathways affected in MIA models — such as microglial activation and oxidative stress — were also found in the placental gene expression patterns in the Nature study.

So the real question becomes: Is paracetamol the problem — or is it the immune response that prompted its use?

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⚖️ Conclusion: Caution, Not Panic

The findings of the recent study are important, but correlation does not equal causation. We must be careful not to jump to conclusions without exploring alternative explanations.

If APAP is acting more like a flag for underlying maternal immune or genetic risk — rather than a toxic agent — then restricting its use may not prevent ADHD, and might even pose risks by leaving maternal fever untreated.

Instead, a more holistic research approach is needed — one that examines:

• Genetic predispositions,

• Immune activation pathways,

• And the true drivers of neurodevelopmental risk.

In the meantime, pregnant women should consult their doctors and not panic about occasional paracetamol use. Medical decisions must be informed by balanced evidence, not alarm.

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📚 References and Further Reading

1. Ji et al. (2025). Associations of maternal blood biomarkers of prenatal APAP exposure with placental gene expression and child attention deficit hyperactivity disorder. Nature Mental Health. https://www.nature.com/articles/s44220-025-00387-6

2. Thapar et al. (2013). What have we learnt about the causes of ADHD? Journal of Child Psychology and Psychiatry, 54(1), 3–16. https://doi.org/10.1111/jcpp.12040