The six causes of AUTISM, according to experts: from painkillers, a common condition and these ‘toxins’, how to escape the disorder that plagues so many

In an announcement that stunned parents and doctors worldwide, American health chiefs have vowed to identify the causes of autism before the end of the month.

The probe is being led by President Donald Trump’s controversial health secretary, Robert F. Kennedy Jr, who said his team will publish a list of environmental exposures that are ‘certainly causing autism’.

‘By September, we will know what has caused the autism epidemic and we’ll be able to eliminate those exposures,’ Kennedy declared.

The report follows President Trump’s comments last week in which he described rising autism diagnoses in the US and elsewhere as ‘a tremendous horror show’.

The claims have provoked outrage from medical leaders, who warn the approach is dangerous and that autism should not be portrayed as a condition to be ‘cured’.

They say such rhetoric risks fueling stigma and encouraging parents to seek out unproven or even harmful treatments – from restrictive diets to bleach-based ‘detox’ regimes – while diverting attention from the support autistic people actually need.

Vaccines are also often cited by campaigners as a key culprit, despite repeated large-scale studies showing no link between childhood immunisations and autism.

A growing number of researchers, however, do accept that environmental factors may in fact play a role in the surge in diagnoses – though not necessarily the ‘toxins’ Kennedy points to.

Autism, a lifelong developmental disorder that makes it difficult for people to understand social cues or express themselves, was once considered rare. Over the past 20 years, however, the number of people living with the diagnosis has surged by almost 800 per cent, according to research in the Journal of Child Psychology and Psychiatry.

It is now thought that about one in every 100 people has the condition – equating to roughly 670,000 Britons and more than 3.3 million Americans.

Some experts say this rise reflects greater awareness and improved clinical understanding, meaning many people who would once have gone undiagnosed are now being identified. But others disagree. Dr Punit Shah, a psychologist and autism specialist at the University of Bath, said: ‘Even controlling for these factors there is evidence of a genuine rise in cases.

‘And while we know that autism is highly heritable, genes do not change in a matter of decades, so there are likely environmental factors leading to this rise.’

Scientists are currently investigating what those factors might be – and say parents should be aware of them. Here, we outline what they are… and vaccines is NOT one of them.

Common condition increases risk

Research has shown that mothers with diabetes are more likely to have a baby diagnosed with autism.

Almost 4.3 million people were living with diabetes in 2021/22, according to the latest UK figures, and numbers continue to climb. About 90 per cent of cases are type 2 diabetes, linked to obesity and usually diagnosed later in life.

Experts say the condition – which affects blood sugar – can alter hormone levels during pregnancy and in turn impact a child’s neurodevelopment. The risk is greatest when women develop diabetes while pregnant – gestational diabetes – which affects five per cent of mothers.

‘This is one finding that is very consistent,’ says Professor Sir Simon Baron-Cohen, an autism expert at the University of Cambridge. ‘When mothers gain too much weight during pregnancy they are at risk of developing gestational diabetes, and in turn are more likely to have a child with autism.

‘This is because the condition changes the levels of sex hormones in the womb, which are crucial for brain development.’

Some women can develop gestational diabetes during pregnancy even if they don’t gain weight. However, experts argue that these women can still avoid some of the complications by keeping blood sugar under control – which typically involves following a low-calorie diet and exercise.

Earlier this year, a review of more than 200 studies, involving 56 million mothers and children, confirmed diabetes in pregnancy was associated with a raised risk of autism. The study by Chinese researchers, published in The Lancet, found children exposed to maternal diabetes were 25 per cent more likely to be diagnosed with autism.

Dirty air may be to blame

Air pollution may also be linked to autism, experts suggest.

A 2024 review of the latest scientific literature, published in the BMJ, found that babies with a higher genetic risk of the disorder who were exposed to four common air pollutants were more likely to develop it.

Scientists believe that when breathed in during early childhood, or during development in the womb, microscopic pollutants can enter the bloodstream. They may then bypass the brain’s protective layers, causing inflammation, altering nerve function and raising the risk of autism.

Professor Frank Kelly, an expert on air pollution and public health at Imperial College London, said: ‘There is now strong research to show that exposure to air pollution either in pregnancy or in early childhood, can contribute to the development of autism.

‘The placenta is there to ensure the foetus has an optimal supply of nutrients, but if chemicals are entering the mother’s body the foetus will have access to those too, and this can cause damage to the brain while it is developing.’

Experts say that while exposure to air pollution cannot be avoided entirely, there are practical steps parents can take.

‘If you live in an urban area or besides a busy road then you should not open windows during rush hour, and when moving about with your child in a pram think about avoiding busy roads,’ says Professor Kelly.

‘Indoor air pollution is also a factor. Wood-burning stoves or gas cookers can have an impact, so making sure you have good ventilation is important.’

Older parents face higher odds

Doctors have long suspected that leaving it later in life to have children may increase the risk of autism – and the evidence is piling up.

One of the largest investigations, covering nearly six million children across five countries, found that fathers over 50 had a 66 per cent greater chance of having a child with autism compared with those in their 20s. Mothers in their 40s saw a 15 per cent rise.

Scientists say that for men, the effect may be genetic, meaning those who have children later in life are more likely to have autism themselves. In older mothers, hormonal changes could play a role in this increased risk.

‘Parental age being linked to an increased likelihood of a child with autism is a finding that is consistent in the research,’ says Professor Baron-Cohen. ‘And both parents’ ages have an impact. For women this is likely because of changes to the hormonal environment in the womb, as they age, which can impact development.

‘For fathers, their role is thought to be genetic.’

Vitamin deficiency linked to problems

A deficiency in an essential vitamin during pregnancy could also increase the risk of autism.

Folate – a B vitamin found in leafy greens or supplements – may cut the risk if taken at the right time. Research suggests mothers who take folic acid during the first months of pregnancy are less likely to have a child with autism. The nutrient is vital for the formation of DNA, and crucial for brain and spinal cord development.

‘Our research has looked at giving folate to children who already have an autism diagnosis,’ said Dr Richard Frye, a child autism specialist at the Rossignol Medical Centre in Arizona. ‘However, we could be tackling this before birth, too, by giving it to pregnant women. We believe as many as 75 per cent of children with autism have low folate levels, and much of that begins in the womb.’

‘There should be no question on whether mothers are taking folic acid before pregnancy and in the early months of pregnancy,’ says Professor Avarahm Reichenberg, an autism expert at Icahn School of Medicine at Mount Sinai University New York.

Obesity in pregnancy doubles danger

Children born to mothers with obesity before or during pregnancy also face a greater risk of autism, experts say.

A 2024 review of 42 studies by researchers at the University of Southern Australia, published in the Journal of Psychiatric Research, analysed data from 3.6 million mothers and found that maternal obesity doubled the associated risk.

Scientists believe inflammation and hormone imbalances may alter brain development.

Painkiller warning for mothers-to-be

Pregnant women should limit paracetamol use.

In a study published last month in Environmental Health, US scientists analysed the health records of more than 100,000 people and found a ‘strong link’ between use of the painkiller and autism risk.

Experts believe paracetamol can disrupt hormone regulation, which is crucial for development of the brain.

Vaccine myth persists despite the evidence

US Health Secretary Robert Kennedy has previously been outspoken on his belief that the measles vaccine increases the risk of an autism diagnosis.

He said: ‘There are adverse events from the [measles] vaccine. It does cause deaths every year. It causes all the illnesses that measles itself causes.’

The claim rose to prominence through disgraced British doctor Andrew Wakefield, who alleged the MMR jab caused autism in a paper published in The Lancet.

The research was later discredited – and Wakefield struck off – after it emerged he had falsified results and had financial conflicts of interest.

‘There is no evidence whatsoever that vaccines are linked to autism,’ says Professor Reichenberg. ‘It is a dangerous theory based on discredited research that is putting children’s lives at risk by not getting crucial vaccines.’

Vitamin therapy gives boy his voice after five years

When Ryan Baldridge Jr was diagnosed with autism at age four, his family were warned he might never speak coherently.

After coming across research around folate treatment online, parents Kim and Ryan Sr took him to see the autism expert Dr Richard Frye in 2023.

Tests showed Ryan, pictured with his younger brother Grayson, had low levels

of folate – a vitamin crucial for brain development. He was prescribed two daily liquid doses of leucovorin, a drug originally developed for chemotherapy but which also boosts folate production.

Within two weeks, Ryan was talking in full sentences and, for the first time, able to use words to express affection for his parents.

‘I’d never experienced an unprompted ‘I love you’ from my son in five years of his life,’ Mr Baldridge told the Daily Mail earlier this year.

‘It was like an explosion of improvement all happening so quickly.’

Ryan, now eight, has gone from ‘basically non-verbal’ in kindergarten to reciting his lines for the upcoming school play.

‘Now you can’t shut him up. He’s doing unbelievably,’ said his father.

But while Ryan’s story is remarkable, not all families report the same. Many parents say they have seen little or no change in their child’s symptoms after trying folate supplements, and experts caution that the evidence is still limited.

Larger, rigorous clinical trials are needed before such treatments can be recommended more widely.