Scientists dispute whether rise driven by increase in prevalence or greater recognition
Autism diagnoses in a large sample from the UK rose by a startling 787 percent from 1998 to 2018, according to a recent paper.
Published in Journal of Child Psychology and Psychiatry, the paper adds to a growing body of research showing increases in the diagnoses of autism spectrum disorder (ASD) throughout the world, including in the United States—yet the government agencies charged with protecting public health remain hesitant to acknowledge or explain the increase in underlying prevalence.
Scientists dispute whether the rise is driven by an actual increase in prevalence or a greater recognition of the disorder by mental health professionals.
The authors of the UK paper used data from the Clinical Practice Research Datalink primary care database. The 6,786,212 patients included in the database in 1998 rose to 9,594,598 by 2018, of whom 65,665 were diagnosed with autism by that point.
The researchers documented a particularly stark rise in autism diagnoses among both females and adults, alongside smaller increases among males and other age groups.
“One adult per 100,000 was diagnosed in 1998, versus twenty in 2018,” the paper reads.
The researchers themselves seem to believe that the increase is based primarily on an increase in recognition of autism in patients, rather than an actual increase in prevalence.
“As there is not really a plausible reason why autism should increase more in adults and females our study suggests the change is probably due to increased identification, and not more people with neurodevelopmental disorders per se.” lead author Ginny Russell, from the University of Exeter, said in a statement.
“The definition of what constitutes autism has changed over time, and females and adults were not often thought of as having autism 20 years ago. The vocal work of charities and media coverage, combined with changes in policy has led to more assessment [centers] for adults, and an autism narrative that many women and girls identify with. Consequently, demand for diagnosis has never been higher.”
Russell further affirmed the team’s conclusion in an emailed statement to The Epoch Times.
“Our paper is about increased recognition and not at all about prevalence,” she wrote.
The authors of the new study noted their work’s limitations, including the incompleteness of data.
“Because of this potential for missing data, we chose not to concentrate on absolute incidence or prevalence rates, rather keeping the analysis focused on a comparative trend in diagnosis over time,” the study reads.
While Russell and her coauthors pinpointed changing diagnostic practices as the key driver of the increase, other experts have stressed that prevalence is genuinely rising, identifying older parental age, environmental pollution, and other factors as potential explanations for the trend.
A 2012 meta-analysis, or analysis of multiple studies, authored by scientists in Sweden, Israel, the UK, and the United States linked advancing maternal age to autism spectrum disorder. A 2006 study from one of the meta-analysis’s authors, Abraham Reichenberg, had previously linked advancing paternal age to the condition.
In the United States, the mean age of mothers increased to 26.3 years in 2014 from 24.9 years in 2000, according to the Centers for Disease Control and Prevention. The mean age of fathers has also gone up, rising to 30.9 years in 2015 from 27.4 in 1972.
Research has also revealed correlations between rates of autism and the presence of certain environmental pollutants, including the herbicide glyphosate, found in Monsanto’s Roundup pesticide.
Walter Zahorodny, an associate professor at Rutgers New Jersey Medical School who leads the New Jersey Autism Study, told The Epoch Times via email that the new UK study is in line with previous research.
“Why don’t thoughtful individuals accept the reality of increasing [ASD] prevalence in spite of overwhelming evidence?” Zahorodny said.
“I wish I knew with confidence the primary drivers of the increase in ASD prevalence.
“Parent age, premature gestation/low birth weight, [and] prenatal exposure to antidepressants and anti-seizure medications are implicated for sure. There is also an indication that prenatal exposure to folic acid and acetaminophen may contribute.
“More research into prenatal environmental exposures is needed. Obviously, genetic factors are NOT likely [to] explain the sharp increases in ASD prevalence since 2000.”
Zahorodny’s colleague Cynthia Nevison, a research associate with the University of Colorado–Boulder who has researched the link between autism and environmental pollution, also spoke with The Epoch Times via email.
“With respect to what could be causing the increase, my comment is this: I think that is a question that reporters should be asking the U.S. Centers for Disease Control and the equivalent agency in the UK,” Nevison said.
“The rise in autism has been going on for over 30 years and, at this point, the public deserves a thoughtful and well-researched answer to [the] causation question.”
On its autism “Frequently Asked Questions” webpage, the Centers for Disease Control and Prevention (CDC) notes that autism diagnoses are on the rise.
“It is unclear exactly how much of this increase is due to a broader definition of ASD and better efforts in diagnosis. However, a true increase in the number of people with an ASD cannot be ruled out. We believe the increase in the diagnosis of ASD is likely due to a combination of these factors,” the webpage reads.
The CDC didn’t respond by press time to a request for comment on the causes of autism, whether the increase is expected to continue, and what it’s doing to curb the increase.
A spokesperson for the UK’s public health agency, Public Health England, told The Epoch Times that the agency wasn’t able to answer its questions on the causes of autism, whether the increase is expected to continue, and what it’s doing to curb the increase.
Nathan Worcester is an environmental reporter at The Epoch Times.