World’s most popular painkiller may increase risk of autism and ADHD

Pregnant women should only take paracetamol on the advice of a doctor, Harvard scientists have warned—amid fears the common painkiller could raise the risk of autism and ADHD in their children.

Paracetamol—known as acetaminophen and often sold under the brand name Tylenol in the US—is widely used by expectant mothers to treat pain, headaches and fever. 

But dozens of studies have already linked it to higher rates of autism and attention deficit hyperactivity disorder (ADHD).

Now US researchers from Mount Sinai and Harvard’s School of Public Health say their analysis of more than 100,000 people is the most comprehensive yet—and provides the ‘strongest evidence so far’ of a link. 

They urged mothers-to-be to use paracetamol sparingly, recommending only ‘the lowest effective dose for the shortest possible time.’

However, the team stressed the findings do not prove the drug directly causes neurodevelopmental disorders—only that the association is consistent and worrying enough to demand further investigation.

Dr Diddier Prada, assistant professor of population health science at Mount Sinai Hospital in New York and co-author of the study, said: ‘Our findings show that higher-quality studies are more likely to show a link between prenatal acetaminophen exposure and increased risks of autism and ADHD.’

He added: ‘Given the widespread use of this medication, even a small increase in risk could have major public health implications.’

But he stressed that women should not suddenly stop taking it. 

‘Pregnant women should not stop taking medication without consulting their doctors. Untreated pain or fever can also harm the baby. 

‘Our study highlights the importance of discussing the safest approach with health care providers and considering non-drug options whenever possible.’

Paracetamol is currently recommended by the NHS as the ‘first choice’ painkiller for expectant mothers, but only for short periods and at the lowest effective dose.

Around half of pregnant women in the UK take paracetamol, and in the US the figure rises to around 65 per cent. 

Health chiefs advise that only certain people — such as those with liver or kidney disease or taking epilepsy medication — need to exercise extra caution.

To reach their conclusion, the US researchers reviewed 46 separate studies involving more than 100,000 participants.

The team collected detailed data on when paracetamol was taken—whether in the first, second or third trimester, or throughout the whole pregnancy—and linked it with mothers’ medical records.

Writing in the journal Environmental Health, they concluded: ‘Ultimately, the obtained scores suggest strong evidence of a likely relationship between prenatal acetaminophen use and increased risk of ADHD in children. 

‘This includes high-quality studies that provide very strong evidence of an association and studies that provide strong evidence of an association.’

They added: ‘There was strong evidence of a relationship between prenatal acetaminophen use and increased risk of autism in children.’

The findings come as demand for autism assessments has reached record levels in the wake of Covid. 

NHS figures show almost 130,000 under-18s in England were waiting for an assessment in December 2024.

Experts have described it as an ‘invisible crisis’, with services repeatedly failing to keep pace with rising demand. 

Last year, the Children’s Commissioner warned that children left languishing for years on waiting lists were effectively being ‘robbed’ of their childhoods.

Autism is not a disease and is present from birth, although it may not be recognised until childhood or even much later in life. 

It exists on a spectrum: while some people can live independently with little support, others may need full-time care.

Meanwhile, NHS figures show more than 230,000 people in England are now prescribed ADHD medication to manage symptoms such as inattention and hyperactivity. 

Prescription rates jumped by a fifth last year — the sharpest annual rise since records began in 2015.

The surge has been driven largely by women in their 20s and 30s, though prescriptions for children are also climbing. 

Experts have voiced concern that some private clinics are over-diagnosing the condition and handing out powerful stimulant drugs too freely.

But others argue that far from being over-diagnosed, many adults are only now getting the help they were long denied. 

ADHD was only formally recognised in the UK as a disorder that persists into adulthood in 2008—until then it was seen solely as a childhood problem that children would ‘grow out of.’

In the US, meanwhile, an estimated 2.3 million children and seven million adults have ASD.

Diagnoses have risen sharply over the past two decades, according to shifting statistics from the Centers for Disease Control and Prevention.

In 2000, about 1 in 150 children received an ASD diagnosis; by 2020, that figure had climbed to 1 in 31, a near-quadrupling that reflects both greater awareness and evolving diagnostic criteria.

The surge in the US is further illustrated in a 2024 study of 12.2 million Americans’ health records, which revealed a 175 percent increase in autism diagnoses over an 11-year period.

While some experts attribute the rise to expanded screening and reduced stigma, others argue that biological and environmental factors may also play a role. This debate continues to divide researchers.