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Children’s Health Defense (CHD) scientists are pushing back against a study in JAMA Psychiatry suggesting that the global increase in autism and attention-deficit/hyperactivity disorder (ADHD) diagnoses is likely driven by broadening diagnostic criteria.
Brian Hooker, Ph.D., CHD chief scientific officer, and Karl Jablonowski, Ph.D., CHD senior research scientist, criticized the authors of the JAMA study for failing to consider that environmental toxins might be driving the increase.
Hooker said the authors overlooked the possibility that there are now so many toxic exposures that it takes very little genetic susceptibility to trigger autism or ADHD. Changes in diagnostic criteria may be a factor, Hooker said, but there is no way that it explains the steep increase in autism and ADHD rates since the 1990s.
Hooker told The Defender:
“What we’re seeing instead is a lowering of the genetic threshold required to reach a toxic tipping point as the toxic load between 1994 and 2016 skyrocketed with the expanding vaccination schedule, acetaminophen use, the GMO [genetically modified organism] revolution, etc.”
The authors of the JAMA study analyzed data from over 37,000 individuals in Denmark diagnosed with autism or ADHD over two decades. They reported that genetic risks for the conditions decreased over time, while diagnoses increased.
The study concluded that since genetic risk didn’t explain the increase in autism and ADHD diagnoses, the global surge in diagnoses was likely because the criteria used for diagnosing the conditions had broadened.
The authors claimed that the diagnosis threshold for autism and ADHD had lowered over time, so that kids who showed only mild symptoms were now being diagnosed.
The researchers examined three hypotheses for why diagnosis rates have increased — none of which took into account environmental toxins.
First, they thought it possible that diagnostic criteria for autism and ADHD may have broadened over time to include kids with milder symptoms.
Second, they thought maybe that psychiatric disorders that previously had been diagnosed as separate from autism or ADHD were getting lumped into autism or ADHD diagnoses.
Third, they speculated that there is now better detection of autism and ADHD than in the past.
Their data matched the first hypothesis but not the other two, they said.
Jablonowski questioned the researchers’ decision to examine only those three hypotheses. “Why did none of the hypotheses take into account the explosion of toxic exposures like pesticides, vaccines and wireless radiation since the 1990s?”
Jablonowski said the authors “never considered that genetic susceptibility to toxic exposures — as in, a person’s genetic risk for autism — could be getting washed out by the avalanche of toxic exposures. Instead, the authors jump to the ‘over-diagnosis’ conclusion when evidence for the genetic risk of autism diminishes.”
Media spin study as disproving vaccine-autism link
An estimated 1 in 31 8-year-old children had an autism spectrum disorder (ASD) diagnosis in 2022 — up from 1 in 36 in 2020, according to the latest data from the Centers for Disease Control and Prevention (CDC).
The global autism rate was about 1 in 127 in 2021, according to the World Health Organization.
There is research suggesting that environmental toxins, including vaccines and Tylenol, can cause autism, especially in genetically susceptible children.
Although the new study made no mention of vaccines, some news outlets reported on the study as if it provided evidence against the vaccine-autism link.
Medical Xpress reported that the study “challenges existing narratives that blame a single environmental factor or vaccines for the increase.”
NewScientist, under the headline, “Autism and ADHD are on the rise due to widening diagnostic criteria,” said the study ran contrary to “unfounded claims about childhood vaccinations and prenatal exposure to paracetamol (acetaminophen).”
Paracetamol and acetaminophen are both names for Tylenol.
In November 2025, the CDC finally revised its autism webpage to say there is no evidence supporting the blanket claim that vaccines do not cause autism.
Patricia Lemer, a licensed counselor and educational diagnostician with decades of experience working with neurodevelopmental disorders, believes that many environmental toxins — including vaccines, wireless radiation, heavy metals and pesticides — are contributing to the rise in autism and ADHD rates.
In her book, “Total Load Theory: Transforming Lives in Autism, ADHD, LD, SPD, and Mental Health,” Lemer argues that autism and ADHD are most likely driven by a complex combination of biological, environmental, immunologic, neurological, psychological and toxicological load factors.
Study data interpretation problematic, says CHD scientist
For the study, the authors looked at changes in the genetic risk profile of individuals diagnosed with ASD or ADHD in Denmark from 1994 to 2016.
They used data from the Lundbeck Foundation Initiative for Integrative Psychiatric Research study, one of the largest studies of genetic and environmental causes of mental disorders worldwide.
To measure genetic risk, the authors generated polygenic scores, or polygenic risk scores, for each person diagnosed with autism or ADHD. The score indicates a person’s overall genetic predisposition to a particular condition.
They also looked at other psychiatric disorders, including depression, bipolar and schizophrenia. And they examined individuals’ polygenic scores for cognitive-behavioral outcomes, including addiction, educational attainment, IQ, neuroticism and risk-taking.
The authors said they based the polygenic scores on genome-wide association studies.
Jablonowski said that was fine — but that the authors inaccurately interpreted what the scores meant.
“The scores showed that genetic risk is not the primary driver of the autism epidemic explosion, something else is. And the authors, while ignoring absolutely every other contributor, conclude that that ‘something else’ must be over-diagnosis.”
The authors ran statistical tests, adjusted for sex, age and ancestry, which showed that a more recent autism or ADHD diagnosis was associated with a decreased genetic risk for autism or ADHD.
They concluded that their findings “suggest that clinical practice and diagnostic criteria have changed over time to include a broader phenotypic manifestation of ASD and ADHD.”
They wrote in their report that the study “offers a new perspective for ongoing debates about increasing diagnostic rates of ASD and ADHD.”
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Although the study authors, led by Sonja LaBianca, M.D., Ph.D, of Copenhagen University Hospital, did not outright deny that environmental factors may also play a role, they wrote that autism and ADHD are “highly heritable” conditions.
The study was funded by the Research Fund of the Mental Health Services, Capital Region of Denmark.
Some of the authors disclosed other funding sources, including the U.S. National Institute of Mental Health, the Independent Research Fund Denmark and the Universities and University Hospitals of Aarhus and Copenhagen.
The study authors did not respond to our request for comment by the deadline.
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