A research group from the Norwegian Institute of Public Health and the University of Oslo has investigated the relationship between paracetamol use in pregnancy and ADHD diagnoses among 112,973 children in the Norwegian Mother and Child Study. The study includes 2,246 children with an ADHD diagnosis.
The group found that short-term use of paracetamol is harmless, for example, for fever in pregnancy. However, children exposed to paracetamol in the womb for 29 days or more were diagnosed with ADHD twice as often as children who were not exposed.
Eivind Ystrøm is a researcher at the Norwegian Institute of Public Health. He explains that about half of the pregnant women in the study had used paracetamol for 1-7 days in pregnancy. He considers this to be responsible and harmless use.
“We found that it was safe to use paracetamol for a few days, for example, for a fever. It may even be beneficial because it reduces the period the foetus is exposed to high temperature," says Ystrøm.
With use of more than 7 days, the study showed that the risk of children being diagnosed with ADHD increased with the length of exposure to paracetamol.
About 4 per cent of Norwegian 13-year-olds have an ADHD diagnosis. Among the children in the study who were exposed to paracetamol for 29 days or more, about 8 per cent had a diagnosis.
"Pregnant women who need pain relief over extended periods of their pregnancy should consult their doctor. For example, if they have migraines and consider using paracetamol for longer periods,” says Ystrøm.
Supports previous research findings
In previous studies, researchers have found an association between long-term paracetamol use during pregnancy and the occurrence of ADHD in children. However, in a previous study, Ystrom has shown that impulsive personality is associated with paracetamol use in pregnancy. This can be interpreted that mothers who use paracetamol in pregnancy may have ADHD symptoms. Therefore, it is uncertain to what degree ADHD has come from long-term paracetamol use, or is inherited from the parents.
This study was adjusted for familial risk of ADHD (heredity), the conditions that paracetamol can relieve and paracetamol use before pregnancy. It found that long-term use doubles the risk.
May be due to other causes
Ystrøm emphasises that although the researchers have found an association, it does not necessarily mean that paracetamol causes ADHD. Researchers also found an association between paternal use of paracetamol during pregnancy and the child's ADHD diagnosis. There is therefore a need for further research before we can comment with greater certainty.
"It is also important to point out that ADHD may have other causes, even though the mother used paracetamol for a long time in pregnancy," says Ystrøm.
Supports advice from drug authorities
The findings support the advice of the drug authorities: paracetamol is the first choice for pain, but all drug use should be restricted during pregnancy.
The Norwegian Medicines Agency advises pregnant women about the medicines they can use during pregnancy. The Norwegian Directorate of Health is responsible for the national guidelines for pregnancy care in Norway, including the use of medicines in pregnancy.
Ystrom E, Gustavson K, Brandlistuen RE, et al. Prenatal Exposure to Acetaminophen and Risk of ADHD. Pediatrics. 2017;140(5):e20163840. DOI: 10.1542/peds.2016-3840