Children of mothers who take paracetamol during pregnancy may be at a higher risk of developing attention deficit/hyperactivity disorder (ADHD), a study has found.
Although experts said that mothers should not be alarmed, the study has prompted calls for further investigations of the effects of paracetamol on the developing brains of babies in the womb.
In an analysis of more than 64,000 children and mothers born in Denmark between 1996 and 2002, researchers from the University of California found that children of mothers who reported taking paracetamol were more likely to have ADHD-like behaviours, or be taking ADHD medication.
While the study could not prove that paracetamol was the cause of the increased risk, experts said that the drug – the most commonly taken during pregnancy – was so widespread that further investigations were essential.
Paracetamol can disrupt the hormonal system in mammals and the scientists behind the study are seeking to establish whether it might affect the hormones essential for the healthy development of babies’ brains while in the womb.
ADHD – the most common behavioural disorder in the UK – is estimated to affect between two and five per cent of school-aged children.
It is characterised by a low attention span in children, hyperactive behaviour and is often linked with learning difficulties.
The rate of diagnosis appears to be rising. Prescriptions for ADHD drugs, including Ritalin, increased by more than 50 per cent between 2007 and 2013.
The causes of ADHD are unknown, although it appears to run in families. However, non-inherited factors may contribute and in recent years scientists have increasingly looked for a cause in environmental factors in early life.
In their study, published in the Journal of the American Medical Association publication, JAMA Pediatrics, researchers also found that women who took paracetamol in each trimester were more likely to have a child who developed ADHD.
Dr Kate Langley, an expert in developmental and health psychology from Cardiff University, said that the findings warranted “further investigation”, but should “be taken with caution”.
“There are many reasons why women take paracetamol during pregnancy and it is possible that it is one of those factors, rather than the taking of paracetamol itself, which leads to a higher risk of childhood ADHD,” she said.
“It may be important to take medications such as paracetamol during pregnancy and pregnant women should continue to follow advice from their own healthcare professionals.”
Professor Jim Stevenson, emeritus professor of developmental psychology at the University of Southampton, said that the study was “carefully conducted and analysed” and backed calls for further investigations into paracetamol’s possible link with ADHD.
“This study should be used as basis for further experimental research not least because exposure to paracetamol during pregnancy is so common,” he said.
However, Philip Asherson, professor of molecular psychiatry at King’s College London, agreed that it was “highly likely” that “confounding effects” rather than paracetamol itself was the cause of increased ADHD risk.
"It is important that people are not alarmed by these findings and do not alter their use of paracetamol… it is far too early to say that the association the researchers observe plays a causal role in ADHD,” he said.