A much-anticipated report on the potential causes of autism is set to be released on Monday by President Trump and Health Secretary Robert F. Kennedy Jr. This topic has been a long-standing focus for both individuals.
Autism diagnoses have significantly risen in the United States over the past quarter-century. Experts attribute much of this increase to heightened awareness and a broader definition of the disorder. However, President Trump and Mr. Kennedy have consistently suggested a link between vaccines and autism, a theory that numerous scientific studies have thoroughly disproven.
This new report is also expected to highlight another potential risk factor: acetaminophen, the active ingredient found in Tylenol and other common painkillers, when used during pregnancy. While this possible connection has been researched over many years, the findings so far remain inconclusive.
Below, we explore what scientists currently understand about autism, its potential causes, and associated risks.
What is Autism Spectrum Disorder?
Officially known as Autism Spectrum Disorder (ASD), this condition encompasses a wide array of social and communication challenges, alongside repetitive behaviors and distinct thinking patterns. The intensity of these symptoms varies considerably, from subtle difficulties to severe impairments. For instance, a child with an ASD diagnosis might only have trouble understanding social cues, while others with more profound cases may require assistance with basic communication or daily living activities. Currently, there’s no medical test like a blood test or brain scan to diagnose autism; instead, diagnoses rely on clinical observations and information provided by parents.
Is There a Genetic Component to Autism?
As a neurodevelopmental disorder, autism has been linked to hundreds of different genes. Scientists largely agree that its development likely stems from an intricate interplay of both genetic predispositions and environmental influences.
Dr. Helen Tager-Flusberg, a psychologist at Boston University, reflects on how significantly the understanding of autism’s genetic roots has evolved: “I remember 30 years ago, geneticists were quite hopeful we’d identify perhaps six to ten genes contributing to autism risk. Today, we know that number is easily in the hundreds. Pinpointing the genetic foundation of autism is proving to be much more complex than we initially thought.”
The Centers for Disease Control and Prevention (CDC) has conducted extensive research into autism’s contributing risk factors. Researchers have investigated numerous potential elements, such as air pollution, exposure to certain toxic chemicals, and viral infections experienced during pregnancy.
Furthermore, some studies indicate a higher risk for babies born to older parents. Other investigations have hinted at a possible association between the condition and factors like premature birth or low birth weight.
What Does Research Say About Acetaminophen and Autism?
For more than ten years, scientists have explored acetaminophen, the active ingredient in Tylenol and other pain relievers. While some studies on pregnant women using acetaminophen have shown a correlation with an increased risk of neurodevelopmental disorders in children later on, other research that accounted for confounding factors, such as genetics, found no such link.
Recently, in 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.
The review’s authors focused solely on existing data and did not introduce new findings regarding acetaminophen’s effects. They reported an observed association between pregnant women who used acetaminophen and a higher risk of ADHD and autism. However, they emphasized that this correlation does not prove causation. Factors like a mother’s overall health during pregnancy or genetic background could explain these differences. A significant 2024 study involving 2.5 million Swedish children further illustrated this point; it found that the link between acetaminophen use and neurodevelopmental disorders disappeared when comparing siblings born to the same mother.
Following the publication of this paper, Dr. Nathaniel DeNicola, an advisor to the American College of Obstetricians and Gynecologists, affirmed that these findings do not alter current medical advice for pregnant patients.
He reiterated, “The paper’s conclusion is consistent with existing recommendations: Tylenol should be used cautiously, at the lowest effective dose, and as infrequently as possible. This approach aligns with the standard care for Tylenol and many other medications, as well as various considerations during pregnancy.”
What About the Claims Linking Vaccines to Autism?
The idea that vaccines might cause autism first emerged in the late 1990s. This stemmed from a study published by British researcher Andrew Wakefield, which claimed to show a connection between the measles, mumps, and rubella (MMR) vaccine and autism in a small group of 12 children.
In the years since, this hypothesis has been conclusively disproven by numerous large-scale studies, including an extensive analysis involving the entire child population of Denmark. Research consistently shows no link between autism and various factors like vaccine types, their ingredients, or the timing of the recommended childhood immunization schedule.
Dr. Wakefield’s controversial 1990 article was officially retracted in 2010, and he subsequently lost his medical license.
Why Are Autism Diagnoses on the Rise?
Roughly 1 in 31 U.S. children now receive an autism diagnosis, a significant increase from 1 in 150 children in the year 2000. This notable rise is largely attributed to the evolving definitions and diagnostic criteria for autism over the past few decades.
Autism was first officially recognized in the third edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980.
A 1987 revision to the DSM broadened the disorder’s definition to encompass children whose symptoms became apparent later, after 30 months of age. The diagnostic criteria expanded from six to 16, and children now only needed to meet half of these 16 criteria, as opposed to all six under the prior guidelines.
The fourth edition of the DSM, released in 1994, further expanded the autism spectrum to include Asperger syndrome, a social communication disorder often characterized by intense focus on specific interests. This was a crucial change, allowing individuals with milder impairments and average or superior intellectual capabilities to receive an autism diagnosis.
The fifth edition of the diagnostic manual, published in 2013, consolidated various related conditions—autism, Asperger syndrome, and PDD-NOS (pervasive developmental disorder-not otherwise specified)—into a single diagnosis: Autism Spectrum Disorder. This edition also introduced the possibility for clinicians to issue a combined diagnosis of ASD and Attention Deficit Hyperactivity Disorder (ADHD).
CDC data on autism diagnoses revealed that while the prevalence of profound autism (characterized by intellectual disability and severe language impairments) increased slightly between 2000 and 2016, other forms of autism diagnoses saw a much steeper rise.
Beyond diagnostic changes, increased societal awareness of autism has significantly contributed to the rise in diagnoses. The widespread availability of special education services in schools starting in the 1990s encouraged parents to pursue a diagnosis for their children. Concurrently, new guidelines recommending universal autism screenings for infants during their 18- and 24-month well-child check-ups have greatly improved early detection rates.
More recently, researchers note that the proliferation of autism discussions on social media platforms is another factor driving increased diagnoses. Videos about autism on TikTok and YouTube have garnered billions of views, and online forums like Reddit have become vital spaces for individuals to connect, share experiences, and explore their own identities.
Dr. Tager-Flusberg ponders if the increase is solely due to diagnostic shifts: “Is there also an actual increase beyond these variables? I would say probably yes, because some of the non-genetic factors associated with autism are also evolving.”
She concludes, “Over time, our understanding of this disorder’s biology has revealed it to be far more intricate than we ever initially conceived.”