Doctors have revealed the myriad of causes of autism spectrum disorder, as diagnoses of the condition surge in the US.
Recent figures suggest rates in kids and adults have tripled in the last decade.
A study in JAMA Network Open found autism diagnoses among all age groups surged 175 percent between 2011 and 2022, from a rate of 2.3 to 6.3 per 1,000 people
And the biggest increase was among young adults ages 26 to 34, with a 450 percent jump.
A host of research points to doctors becoming better at diagnosing the condition due to more screening and a broader diagnostic criteria.
But, more and more, other factors are being considered behind the rise, including environmental factors like increased exposure to pollution and pesticides.
Dr Cooper Stone, a psychiatrist in Philadelphia, told DailyMail.com exposure to toxic metals, pesticides, and pollution could also play a role in the surge.
He said: ‘There is a strong belief that environmental factors may in part be implicated in developing this condition. While no direct environmental causes have been linked to ASD, there are many associated risk factors that seem to have a relation.’
About one in 36 US children and one in 50 adults have autism, according to the CDC.
Generally, most with the disorder are diagnosed by age five, though some can be tested as young as age two.
Children between ages five and eight were still the most likely group to be diagnosed, at a rate of 30 per 1,000.
The condition is marked by repetitive behaviors, interests, and activities; deficits in social communication and social interaction; and the presence of high or low sensory sensitivity.
There is no cure, but doctors may provide therapies to help with symptoms.
A review published last year found people with a genetic predisposition to autism, such as a parent having the condition, who were exposed to pollution in early life were more likely to develop autism than those exposed to less pollution.
Older research from Harvard also found exposure to air pollution like particulate matter in early childhood may raise the risk of ASD by as much as 64 percent.
While in the womb, exposure to particulate matter may raise risk of ASD by 31 percent.
An Australian study published earlier this year also found boys exposed to endocrine-disrupting chemical Bisphenol A (BPA) in the womb were six times more likely to be diagnosed with autism before age 11 than those without exposure.
That team suggested BPA – which lines plastic and metal food packaging – was associated with neurological and behavioral changes associated with autism.
The US has also seen a surge in the use of synthetic pesticides, which same say could be a contributor, as well.
Use of these chemicals increased 50-fold since 1950.
In 1952, for example, just one in 10 corn fields used pesticides to help kill pests. But by 1982, 95 percent of corn fields used them.
Some research indicates up to 80 percent of Americans have detectable levels of pesticides in their blood.
Earlier this year, the EPA announced an emergency suspension of the pesticide dimethyl tetrachloroterephthalate (DCPA or Dacthal) due to evidence suggesting babies exposed to it in the womb could be born underweight and with a decreased IQ and development.
A recent study also suggested unborn babies exposed to traffic-related air pollution had a higher likelihood of being diagnosed with autism.
Additionally, a 2021 review found ‘the odds of an autism diagnosis were 3.3 times higher in individuals born preterm than in the general population,’ as premature babies are vulnerable to birth complications and inflammation associated with autism.
This means the increase in autism could be due to more preterm babies surviving birth, as the survival rate has increased from 76 percent between 2008 and 2012 to 78 percent between 2013 and 2018, according to research from the National Institutes of Health (NIH).
About one in 10 babies in the US are born preterm, according to the CDC, meaning they are born before 37 weeks gestation.
Some experts also believe the surge is because doctors have gotten better at recognizing and diagnosing the condition.
This also means older people with autism may have never been properly evaluated and are only just receiving their diagnosis.
In 2013, officials from the American Psychiatric Association updated the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), which is used to diagnose mental conditions like anxiety, depression, and bipolar disorder.
The changes collapsed autism, Asperger syndrome AND pervasive developmental disorder into one category, autism spectrum disorder.
This may have led to more children being considered autistic.
Dr Courtney Scott, Medical Director of Momentous Recovery Group, told DailyMail.com: ‘The introduction of new diagnostic criteria by the DSM-5 has resulted in the considerably wider range of presentations and behaviors that clinicians associate with autism spectrum disorder (ASD).
‘This strategy is beneficial because it also includes milder or less typical symptoms of ASD, so that more people with this disorder who were likely to be missed previously are able to be provided with comprehensive support resources.
‘Such an increase in the number of diagnoses could also be explained, in some degree, by this expanded viewpoint.’
Dr Stone said social media sites like TikTok have brought more attention to the condition, especially with groups less likely to be diagnosed like adults and girls sharing symptoms that they had overlooked.
He said: ‘Though in many cases social media can be a great purveyor of misinformation on the subject, it still results in more individuals seeking a diagnostic evaluation, and some portion of those individuals receiving a diagnosis.’
Last year, researchers at the University of South Carolina looked at data from 700,000 children to map counties where autism is most prevalent.
Using this data, they found hot spots in the Southeast, East coast and Northeast. Rates were specifically high in New Jersey, ranking between 2.6 and 8.1 percent of the total population of children.
Meanwhile, rates were especially low in the Texas Panhandle and in Oklahoma.
The experts suggested these areas could have a higher rate of diagnoses due to pollution from urban populations and more access to therapists and screening programs.
While none of this research has found a definitive cause, Dr Scott said that it could help spot the condition earlier and prevent it.
He said: ‘Although no causes have so far been achieved, [study] results are helping unravel the enigma of ASD and in the long-run assist in the formulation of better ways of preventing and treating the condition.’
