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Large Hong Kong Sibling Study Finds No Link Between Prenatal Acetaminophen and Autism or ADHD

Sibling comparisons plus negative-control tests point to family and illness-related confounding with residual uncertainty from incomplete capture of over-the-counter use.

Overview

  • The JAMA Internal Medicine paper published June 29, 2026 used sibling-matched analyses and found no association between prenatal acetaminophen and autism (adjusted HR 1.00) or ADHD (adjusted HR 1.01).
  • Conventional cohort analyses in the same data showed modest positive risks, but those signals disappeared in both negative-control tests and sibling comparisons, which control for family factors and reasons women take the drug.
  • Researchers examined electronic health records from 2001–2023 starting with 708,020 mother–child pairs and used sibling sets that included 124,333 children for autism and 97,285 for ADHD with median follow-ups near 10–11 years.
  • The study’s main limitation is that public EHRs captured prescription or clinic-dispensed acetaminophen but likely missed over-the-counter and private-sector use, leaving a small residual uncertainty about unrecorded exposure.
  • The findings reinforce similar sibling-design and Danish studies and suggest clinicians and public communicators should weigh this accumulating evidence when advising pregnant women about using acetaminophen for fever or pain.