Pain killer Paracetamol (Acetaminophen) use in pregnancy linked to ADHD

Acetaminophen, also known as Paracetamol in UK or Tylenol in US, a common pain reliever considered safe for pregnant women, has been linked for the first time to an increased risk of attention deficit and hyperactivity disorder in children, said a study, published Monday.

More studies are needed to confirm the findings, but experts said the research points to a new potential cause for the worldwide rise in cases of ADHD, a neuro-behavioural condition which has no known cause and affects as many as five percent of US children.

Women who took acetaminophen, also known as Paracetamol, while pregnant had a 37 percent higher risk of having a child who would be later given a hospital diagnosis of hyperkinetic disorder, a particularly severe form of ADHD, said the study in February 24 edition of the Journal of the American Medical Association (JAMA) Pediatrics: doi:10.1001/jamapediatrics.2013.4914.

Compared to women who did not take Acetaminophen while pregnant, women who did also had a 29 percent higher chance of having children who were later prescribed medications for attention deficit hyperactivity disorder, and a 13 percent higher chance of exhibiting ADHD-like behaviours by age seven.

Previous research has suggested that Acetaminophen can interfere with normal hormone function and may affect the developing fetal brain.

The painkiller has also been linked to a slightly increased risk in boys of cryptorchidism, a condition in which the testicles do not descend.

The latest research was based on survey data on more than 64,000 Danish women from 1996 to 2002.

More than half said they took Acetaminophen at least once during pregnancy.

Peer group experts cautioned that; 'The observational findings do not prove that taking Paracetamol or Tylenol-like pain relievers causes ADHD, only that a preliminary link between the two has appeared and would need to be confirmed by further research.'

Miriam Cooper

"Findings from this study should be interpreted cautiously and should not change practice," said an accompanying editorial in JAMA Pediatrics by Miriam Cooper and colleagues at the Cardiff University Institute of Psychological Medicine and Clinical Neurosciences.

"However, they underline the importance of not taking a drug's safety for granted, especially during pregnancy."

The reasons the women took the painkillers could have also had a confounding effect on the outcome, they added.

The study was led by Zeyan Liew, of the University of California, Los Angeles, and was co-authored by Jorn Olsen of the University of Aarhus in Denmark.

Acetaminophen and Asthma

The sharp worldwide increase in childhood asthma over the past 30 years has long perplexed researchers, who have considered explanations as varied as improved hygiene and immunizations. Over the last decade, however, a new idea has emerged.

The asthma epidemic accelerated in the 1980s, some researchers have noted, about the same time that aspirin was linked to Reye’s syndrome in children. Doctors stopped giving aspirin to children with fevers, opting instead for acetaminophen.

In a paper published in The Annals of Allergy and Asthma Immunology in 1998, Dr. Arthur Varner, then a fellow in the immunology training program at the University of Wisconsin School of Medicine, argued that the switch to acetaminophen might have fueled the increase in asthma.

Since then, more than 20 studies have produced results in support of his theory, including a large analysis of data on more than 200,000 children that found an increased risk of asthma among children who had taken acetaminophen.


In November, Dr. John T. McBride, a pediatrician at Akron Children’s Hospital in Ohio, published a paper in the journal Pediatrics arguing that the evidence for a link between acetaminophen and asthma is now strong enough for doctors to recommend that infants and children who have asthma (or are at risk for the disease) avoid acetaminophen.

Dr. McBride based his assertion on several lines of evidence. In addition to the timing of the asthma epidemic, he said, there is now a plausible explanation for how acetaminophen might provoke or worsen asthma, a chronic inflammatory condition of the lungs.


Even a single dose of acetaminophen can reduce the body’s levels of glutathione, an enzyme that helps repair oxidative damage that can drive inflammation in the airways, researchers have found.

“Almost every study that’s looked for it has found a dose-response relationship between acetaminophen use and asthma,” Dr. McBride said. “The association is incredibly consistent across age, geography and culture.”

A statistical link between acetaminophen and asthma has turned up in studies of infants, children and adults. Studies have also found an increased risk of asthma in children whose mothers who took acetaminophen during pregnancy.


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