A significant report from President Trump and Health Secretary Robert F. Kennedy Jr. is anticipated on Monday, focusing on potential causes of autism—a subject both leaders have long been deeply concerned about.
Over the past 25 years, autism diagnoses in the United States have seen a substantial rise. While experts primarily attribute this increase to heightened awareness and evolving diagnostic criteria, both President Trump and Mr. Kennedy have previously suggested a link to vaccines. This theory, however, has been widely debunked by numerous scientific studies.
The upcoming report is also expected to highlight another potential risk factor: acetaminophen, commonly found in painkillers like Tylenol, when used during pregnancy. While this possible connection has been researched for years, the findings so far remain inconclusive.
Let’s explore what scientists currently understand about autism, its potential causes, and associated risks.
What is Autism?
Autism spectrum disorder (ASD) encompasses a wide array of social and communication challenges, along with repetitive behaviors and unique thinking styles. The severity of these symptoms can differ greatly, ranging from mild difficulties with social cues to severe impairments where a child might struggle with speech or basic self-care. Currently, there are no definitive medical tests like blood tests or brain scans for diagnosing autism; instead, diagnosis relies on clinical observations and parental reports.
Could Genetics Play a Role?
Hundreds of genes have been linked to autism, a complex neurodevelopmental disorder. Scientists widely believe that it emerges from an intricate interplay between genetic predispositions and environmental elements.
According to Helen Tager-Flusberg, a psychologist at Boston University, “Thirty years ago, geneticists were hopeful we’d identify perhaps six to ten genes contributing to autism risk. Now, we understand that number is in the hundreds. Unraveling the genetic basis of autism has proven far more complex than initially conceived.”
The Centers for Disease Control and Prevention (CDC) has conducted extensive research into autism risk factors, investigating numerous potential contributors such as air pollution, exposure to toxic chemicals, and viral infections during pregnancy.
Certain studies indicate an increased risk of autism in babies born to older parents. Additionally, research has hinted at associations between the condition and factors like premature birth or low birth weight.
What Do We Know About Acetaminophen and Autism?
For over a decade, scientists have investigated acetaminophen, the active ingredient in Tylenol and similar pain relievers. While some studies on pregnant women’s acetaminophen use have shown a potential for increased neurodevelopmental disorder risks in children, other research, which accounted for confounding factors like genetics, found no such connection.
In August, a review published by researchers from Harvard T.H. Chan School of Public Health and the Icahn School of Medicine at Mount Sinai analyzed 46 prior studies concerning acetaminophen use during pregnancy, with eight specifically focusing on autism.
This review, which synthesized existing data rather than introducing new findings, identified an association between prenatal acetaminophen use and conditions like ADHD and autism. However, the authors emphasized that this correlation does not prove causation. Factors such as a mother’s health during pregnancy or her genetic makeup could explain these observed differences. Notably, a significant 2024 study involving 2.5 million Swedish children found that the link between acetaminophen and neurodevelopmental disorders disappeared when researchers compared 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 do not alter current medical advice for pregnant patients.
He reiterated, “The paper’s conclusion supports the careful use of Tylenol—at the lowest effective dose and least frequent interval. This aligns perfectly with existing standard care for Tylenol and many other medications often encountered during pregnancy.”
What About the Link to Vaccines?
The idea that vaccines might cause autism gained considerable attention in the late 1990s after British researcher Andrew Wakefield published a study of 12 children, claiming a connection between the measles, mumps, and rubella (MMR) vaccine and autism.
However, this hypothesis has been conclusively disproven over the years by numerous extensive studies, including one that encompassed the entire child population of Denmark. Across various vaccine types, their ingredients, and different childhood immunization schedules, no credible link to autism has ever been found by researchers.
Dr. Wakefield’s original 1990 article was officially 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 receive an autism diagnosis, a significant jump from 1 in 150 in 2000. This upward trend is primarily driven by how autism has been defined and diagnosed over the past several 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 definition to include children whose symptoms emerged later, beyond 30 months of age. Diagnostic criteria also expanded from six to 16 points, with children now needing to meet only half of the new criteria, a significant change from needing to meet all six previous criteria.
The fourth edition of the DSM, released in 1994, further expanded the autism spectrum to include Asperger syndrome. This condition is characterized by social difficulties, intense focus on specific interests, and other traits. This inclusion was a major shift, allowing individuals with milder symptoms and average to above-average intelligence to receive an autism diagnosis.
In 2013, the fifth edition of the DSM consolidated various classifications—autism, Asperger syndrome, and PDD-NOS (pervasive developmental disorder-not otherwise specified)—into the single umbrella term of autism spectrum disorder. It also permitted clinicians to issue a dual diagnosis of ASD and attention deficit hyperactivity disorder (ADHD).
CDC data on autism diagnoses revealed a modest increase in the prevalence of profound autism (characterized by intellectual disability and severe language impairments) between 2000 and 2016, while other forms of autism diagnoses saw much steeper rises.
Heightened public awareness has also been a key factor in the increase in diagnoses. The widespread availability of special education services in schools starting in the 1990s encouraged parents to seek diagnoses for their children. Furthermore, pediatricians began recommending universal screening for infants during their 18- and 24-month well-child visits, leading to earlier detection.
More recently, the surge in discussions about autism on social media platforms is also contributing to the rise in diagnoses. Videos related to autism on TikTok and YouTube have collectively garnered billions of views, and online communities on platforms like Reddit have fostered a sense of belonging and identity for many.
Dr. Tager-Flusberg noted, “Is there also a possibility of an actual increase beyond these variables? I would lean towards yes, because some of the non-genetic factors associated with autism are also evolving.”
She concluded by stating, “As time progresses, our understanding reveals that the biology of this disorder is far more intricate than we ever initially conceived.”