Acetaminophen Linked to Hyperactivity and Behavior Problems in Children

By Pat Anson, PNN Editor

A new study is adding to the growing body of evidence linking maternal use of acetaminophen to hyperactivity and other behavioral problems in children. Acetaminophen – which is more commonly known as paracetamol outside the U.S. – is the world’s most widely used over-the-counter pain reliever.

British researchers have been following over 14,000 children born in 1991 and 1992 who are enrolled in the Avon Longitudinal Study of Parents and Children. The children’s health, cognitive skills, temperament and behavior were regularly evaluated as they grew older.

Children with mothers who regularly used acetaminophen in mid to late pregnancy were more likely to be hyperactive, less adaptable and to have conduct problems in their pre-school years. The attention and hyperactivity issues appear to lessen by age 7, although boys exposed to the drug were more likely to have conduct problems until age 9.

“We have shown that paracetamol consumption between 18 and 32 weeks gestation was associated with adverse trends in pre‐school child behaviour, but the associations were no longer present by the end of primary school (age 10‐11 years). Boys appeared to be more susceptible than girls to possible behavioural effects of the drug,” researchers reported in the journal Paediatric and Perinatal Health.

Acetaminophen is used by over half the pregnant women in the United States and European Union. It is the active ingredient in Tylenol, Excedrin, and hundreds of pain medications.

Previous studies have linked maternal use of acetaminophen to asthma, autism and attention deficit disorder (ADHD) in children, as well as early puberty and slow language development in girls.

“Our findings add to a series of results concerning evidence of the possible adverse effects of taking paracetamol during pregnancy such as issues with asthma or behaviour in the offspring,” said lead author Professor Jean Golding of the University of Bristol.


“It reinforces the advice that women should be cautious when taking medication during pregnancy and to seek medical advice where necessary.”

Despite the findings, the UK’s National Health Service (NHS) maintains that it is “usually safe” for pregnant women to use paracetamol.

“Paracetamol has been used routinely during all stages of pregnancy to reduce a high temperature and for pain relief. There's no clear evidence it has any harmful effects on an unborn baby,” the NHS says on its website.

The FDA’s warning label for acetaminophen cautions people about the risk of liver damage and other side effects, but does not specifically warn pregnant women about using the pain reliever. The agency said in 2015 that the evidence was “too limited” to justify such a warning.  

Acetaminophen May Slow Language Development

By Pat Anson, Editor

Another study has linked acetaminophen to learning difficulties in young children born to mothers who used the over-the-counter pain reliever during pregnancy.

Researchers at the Icahn School of Medicine in New York City say toddlers exposed to acetaminophen in the womb had a slower rate of language development at 30 months. The findings are consistent with other studies reporting higher rates of autism, attention deficit disorder (ADHD) and behavioral problems in children born to mothers who used acetaminophen while pregnant.  

Acetaminophen (paracetamol) is one of the most widely used pain relievers in the world. It is the active ingredient in Tylenol, Excedrin, and hundreds of other pain medications. Researchers say over half the pregnant women in the United States and European Union use the drug.


“Given the prevalence of prenatal acetaminophen use and the importance of language development, our findings, if replicated, suggest that pregnant women should limit their use of this analgesic during pregnancy,” said senior author Shanna Swan, PhD, Professor of Environmental and Public Health at the Icahn School of Medicine at Mount Sinai.

“It’s important for us to look at language development because it has shown to be predictive of other neurodevelopmental problems in children.”

The study involved 754 women who enrolled in the Swedish Environmental Longitudinal, Mother and Child, Asthma and Allergy study (SELMA) during weeks 8-13 of their pregnancy. Researchers asked the women to report the number of acetaminophen tablets they took between conception and enrollment, and tested the acetaminophen concentration in their urine.

A delay in a child's language development, defined as the use of fewer than 50 words at 30 months of age, was measured by a nurse and a follow-up questionnaire filled out by the mothers.

Girls born to mothers with high exposure -- those who took acetaminophen more than six times in early pregnancy -- were nearly six times more likely to have language delay than girls born to mothers who did not take acetaminophen.

While the number of acetaminophen tablets and concentration in urine were associated with a significant increase in language delay in girls, there was only a slight increase in boys.  The findings suggest that acetaminophen use in pregnancy results in the loss of the well-recognized female advantage in language development in early childhood.

The study is published online in the journal European Psychiatry. Researchers will follow-up with the children and re-examine their language development at age seven.

A 2016 study of over 2,600 Spanish women linked acetaminophen to autism and attention deficit problems in their children. Studies in Denmark and New Zealand have also linked acetaminophen to a higher risk of ADHD.

Over 50 million people in the U.S. use acetaminophen each week to treat pain and fever. The pain reliever has long been associated with liver injury and allergic reactions such as skin rash. In the U.S. over 50,000 emergency room visits each year are caused by acetaminophen, including 25,000 hospitalizations and 450 deaths.