Summary: This was one of the largest studies of its kind. Researchers looked at the medical records of almost 2.5 million children. They were known to have brain development disorders (neurodevelopmental disorders). About 6% had been exposed to acetaminophen in the womb. The first look raised some doubt about a link between acetaminophen in pregnancy and these disorders. But a second look that compared siblings found no link.
Acetaminophen is used all over the world. It is one of the most common drugs for mild to moderate pain, chronic pain, and fever. It is also one of the safest drugs, so you can buy it without a prescription. That means millions of people use it. It is also in many cold and flu products like Theraflu, Excedrin, and Mucinex, to name a few. Even though it is proven safe, some concerns remain.
In the last few decades, cases of autism, ADHD, and intellectual disability in children have risen. These are brain development disorders. Their risk can rise from exposure to certain substances during pregnancy or from certain lifestyle choices. Acetaminophen is one of the most widely used painkillers. So it is vital to know if it raises the risk of these problems.
But finding what raises the risk of problems like autism and ADHD is hard. These problems do not always cause severe disability. And the rules for diagnosing them keep changing. That changes how many children get diagnosed. That is why they are diagnosed much less often in developing nations. Richer nations have stricter rules and more public awareness.
Does taking acetaminophen (Tylenol) during pregnancy cause autism or ADHD?
The study looked at data on 2,480,797 children born from 1995 to 2019 in Sweden. Of them, 185,909 were exposed to acetaminophen during pregnancy. Studies this big are possible now because health records are electronic and computers can analyze them.
At first, the study found that acetaminophen did raise the risk of these problems. Here is the risk in children not exposed vs. exposed: 1.33% vs. 1.53% for autism, 2.46% vs 2.87% for ADHD, and 0.70% vs 0.82% for intellectual disability. As you can see, the gap between the two groups was tiny. So no one could say for sure that even this tiny rise came from acetaminophen and not something else.
The gap was small, but the researchers wanted to know why it showed up at all. So they took every child diagnosed with autism, ADHD, or intellectual disability. They compared each one with brothers and sisters who were not exposed to acetaminophen in pregnancy. This showed no difference between the two groups. That confirmed the tiny rise found earlier was not from the drug. It came from genetic differences between the groups or other family factors.
What does this study mean for acetaminophen use in pregnancy?
Acetaminophen has been used in medicine for more than half a century. It is known as one of the safest painkillers. It is used for both sudden and chronic pain. Over the years, billions of people have taken it. So its safety is well proven. Still, some doubts remain about its role in brain development problems in children.
But this study is one of the largest so far. It has ended the debate over whether this common painkiller raises the risk of brain development problems. Even the first data showed no real link. Acetaminophen in pregnancy did not clearly raise the risk of ADHD, autism, or intellectual disability in children. And the second look confirmed that even the tiny risk seen at first came from family factors. These include genetic differences between the groups.
Frequently asked questions
How large was the Swedish acetaminophen and autism study?
It is one of the largest studies so far. Researchers looked at the records of 2,480,797 children born in Sweden from 1995 to 2019. Of them, 185,909 were exposed to acetaminophen during pregnancy. Studies this big are possible because computers can now analyze electronic health records. That lets researchers follow millions of children at once.
Did children exposed to acetaminophen before birth have higher rates of autism or ADHD?
At first glance, very slightly. Autism was 1.33% in unexposed children and 1.53% in exposed children. ADHD was 2.46% vs 2.87%. Intellectual disability was 0.70% vs 0.82%. The gaps were so small that no one could say they came from the drug and not something else. So the researchers looked deeper with a sibling comparison.
What is a sibling comparison, and why does it matter?
It takes children diagnosed with autism, ADHD or intellectual disability. It compares them with their own brothers and sisters who were not exposed to acetaminophen in pregnancy. Siblings share much of their genes and family background. When the researchers made that comparison, the difference disappeared. So the small gap seen at first came from genetic and family factors, not from the drug.
Why are autism and ADHD diagnosed more often than in the past?
Cases of autism, ADHD and intellectual disability have risen over the last few decades. Part of the reason is how they are diagnosed. The rules for diagnosis keep changing, and that shifts how many children get a diagnosis. That is also why these conditions are diagnosed far more often in richer nations. There, the rules are clearer and awareness is greater.
References
Ahlqvist, V. H., Sjöqvist, H., Dalman, C., Karlsson, H., Stephansson, O., Johansson, S., Magnusson, C., Gardner, R. M., & Lee, B. K. (2024). Acetaminophen Use During Pregnancy and Children’s Risk of Autism, ADHD, and Intellectual Disability. JAMA, 331(14), 1205–1214. https://doi.org/10.1001/jama.2024.3172
Dr. Gurpreet Singh Padda, MD, MBA, MHP
