A much-anticipated report on the potential causes of autism, a topic long central to President Trump and Health Secretary Robert F. Kennedy Jr., is set to be released on Monday.
Over the past quarter-century, autism diagnoses in the U.S. have significantly risen. While specialists attribute much of this rise to greater public awareness and an evolving definition of the disorder, President Trump and Mr. Kennedy have repeatedly suggested a link to vaccines – a claim overwhelmingly refuted by numerous scientific studies.
This new report is also expected to highlight another potential risk factor: acetaminophen, the active ingredient found in the widely used painkiller Tylenol, when taken during pregnancy. This possible connection has been investigated previously, but the scientific findings remain inconclusive.
Let’s delve into what researchers currently understand about autism, its causes, and associated risks.
Understanding Autism: What is it?
Officially known as Autism Spectrum Disorder, or ASD, this condition encompasses a broad range of challenges related to social interaction, communication, and patterns of repetitive behaviors and thoughts. Symptoms vary dramatically in severity. Some children might only find social cues difficult to navigate, while others with more severe cases may experience significant impairments, affecting their ability to speak or manage basic self-care. Importantly, there isn’t a medical test like a blood test or brain scan to diagnose autism; instead, diagnosis relies on careful observation by clinicians and detailed information shared by parents.
Is There a Genetic Link to Autism?
Autism is a neurodevelopmental disorder, and while hundreds of genes have been linked to it, scientists largely agree that it arises from a intricate interplay of both genetic and environmental elements.
Helen Tager-Flusberg, a psychologist at Boston University, recalls the early optimism among geneticists three decades ago, who believed only a handful of genes (perhaps six to ten) might contribute to autism risk. Today, she notes, that number is understood to be in the hundreds. ‘Pinpointing the genetic underpinnings of autism has become a much more intricate puzzle than we initially conceived,’ she added.
The Centers for Disease Control and Prevention has undertaken extensive research into autism risk factors. Their large-scale studies, along with others, have investigated numerous potential contributors, ranging from air pollution and exposure to toxic chemicals to viral infections experienced during pregnancy.
Some studies indicate that children born to older parents might face a slightly higher risk. Additionally, other research hints at a possible association between the condition and factors like premature birth or low birth weight.
Acetaminophen and Autism: What Does the Research Say?
For more than ten years, scientists have scrutinized acetaminophen, the active ingredient in Tylenol and similar pain relievers. While some studies on pregnant women’s use of acetaminophen have suggested a higher risk of neurodevelopmental disorders in their children later on, other studies that carefully accounted for influencing factors, including genetics, have found no such connection.
Last August, a comprehensive review was published by researchers from the Harvard T.H. Chan School of Public Health and the Icahn School of Medicine at Mount Sinai. This review analyzed 46 prior studies concerning acetaminophen use during pregnancy, with eight of these focusing specifically on autism.
These researchers focused solely on existing studies, offering no new data on acetaminophen’s direct effects. They identified an association between pregnant women’s acetaminophen use and diagnoses of ADHD and autism, but explicitly stated this did not prove the drug caused these conditions. They noted that women using Tylenol might have other significant differences from those who didn’t, such as varying health conditions during pregnancy or distinct genetic profiles. A significant 2024 study in Sweden, involving 2.5 million children, further supported this by finding that the link between acetaminophen and neurodevelopmental disorders vanished when comparing siblings born to the same mother.
Following the publication of this review, Dr. Nathaniel DeNicola, an advisor to the American College of Obstetricians and Gynecologists, affirmed that the findings did not alter existing medical advice for pregnant patients.
Dr. DeNicola explained that the paper’s conclusion reinforced the standard recommendation: ‘Tylenol should be used judiciously in the lowest dose, least frequent interval.’ He emphasized that this cautious approach aligns with current medical guidelines not just for Tylenol, but for many medications and other exposures during pregnancy.
The Vaccine Connection: A Debunked Theory
The idea that vaccines might lead to autism first gained public attention in the late 1990s, when a British researcher, Andrew Wakefield, published a study involving just 12 children. This study controversially claimed a link between the measles, mumps, and rubella (MMR) vaccine and autism.
However, this theory has since been thoroughly and repeatedly discredited by numerous extensive studies, including one groundbreaking research effort that examined the entire child population of Denmark. Across all investigations, no connection has been found between autism and the types of vaccines, their ingredients, or the timing of the recommended childhood vaccination schedule.
In fact, Dr. Wakefield’s original article from 1990 was retracted in 2010, and he subsequently lost his medical license.
Why Are Autism Diagnoses on the Rise?
Today, approximately 1 in 31 U.S. children are diagnosed with autism, a significant increase from 1 in 150 in the year 2000. This notable rise is largely attributed to the evolving definitions and diagnostic criteria for autism over recent decades.
Autism was first officially recognized in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM) in its third edition, published in 1980.
A 1987 revision of the DSM broadened the definition to include children whose symptoms emerged later, beyond 30 months of age. Furthermore, the number of diagnostic criteria expanded from six to sixteen, and children only needed to meet half of these new criteria, a notable shift from the previous requirement of fulfilling all six.
The fourth edition of the DSM, released in 1994, brought Asperger syndrome onto the autism spectrum. This was a crucial change, as it allowed individuals with milder challenges, and often average or even above-average intelligence, to receive an autism diagnosis.
In 2013, the fifth edition of the diagnostic manual streamlined several conditions—autism, Asperger syndrome, and PDD-NOS (pervasive developmental disorder-not otherwise specified)—into a single diagnosis: Autism Spectrum Disorder. This edition also permitted clinicians to issue a dual diagnosis of ASD and Attention Deficit Hyperactivity Disorder (ADHD).
Statistics from the Centers for Disease Control and Prevention indicate that while the prevalence of profound autism (characterized by intellectual disability and severe language impairments) saw a slight increase between 2000 and 2016, other forms of autism diagnoses experienced a much steeper rise.
A heightened public awareness of autism has also been a major contributor to the surge in diagnoses. The widespread availability of specialized educational services since the 1990s has encouraged parents to pursue a diagnosis for their children. Concurrently, new guidelines recommending universal screening for infants during their 18- and 24-month well-child checkups have further promoted early detection.
More recently, researchers note the growing influence of social media in increasing diagnoses. Autism-related videos on platforms like TikTok and YouTube have garnered billions of views, and online communities on forums such as Reddit have provided spaces for individuals to connect and explore their identity.
Dr. Tager-Flusberg poses the question: ‘Is it possible there’s an actual increase in autism prevalence beyond these influencing factors?’ She believes ‘probably yes,’ suggesting that some non-genetic elements linked to autism are also undergoing changes over time.
She concludes, ‘Over time, we’ve come to grasp that the biological underpinnings of this disorder are far more intricate than anyone could have initially conceived.’