Key facts
- A sibling-matched study found no association between prenatal acetaminophen (Tylenol) use and autism or ADHD.
- The analysis included over 124,000 sibling-matched children for autism and over 97,000 for ADHD.
- No link was found regardless of acetaminophen dosage, timing during pregnancy, frequency of use, or maternal age.
- Researchers suggest previous positive findings may be due to unmeasured familial confounding, not a direct drug effect.
- Similar results were observed in large sibling-matched studies in Sweden and Japan.
A recent study employing a sibling-matched design has found no link between prenatal acetaminophen (Tylenol) use and the development of autism or attention-deficit/hyperactivity disorder (ADHD) in children. The research, which included over 124,000 sibling-matched children for the autism analysis and more than 97,000 for the ADHD analysis, aimed to control for genetic and shared environmental factors within families.
The findings indicate that the dosage, timing, frequency of acetaminophen use during pregnancy, or the mother's age at the time of pregnancy did not correlate with an increased risk of these neurodevelopmental conditions. The researchers concluded that the positive associations observed in some previous studies, which did not use sibling matching, likely stem from residual familial confounding rather than a direct pharmacological effect of the medication.
This conclusion is supported by a "negative control" analysis where an association was found even when comparing children whose mothers used acetaminophen before pregnancy or after birth to those who did not use the painkiller, an outcome deemed biologically implausible. The study's results align with similar large sibling-matched studies conducted in Sweden in 2024 and Japan in 2025, reinforcing the lack of a causal relationship.