Sorting Facts From Misinformation About Autism

Helen Tager-Flusberg, Ph.D.

Credit: Boston University

When new autism statistics are released, it’s natural for families to feel concerned. But according to Helen Tager-Flusberg, Ph.D., professor at Boston University and founder of the Coalition of Autism Scientists, this rise does not signal an epidemic. Instead, it reflects progress: Health care providers are now better at recognizing autism, referring children for diagnosis and connecting families with services earlier. In a recent interview with The Educated Patient, Tager-Flusberg explained what families should know about the causes of autism, the current state of research and why claims linking autism to medications like Tylenol are not supported by strong scientific evidence.

Last spring, the Centers for Disease Control and Prevention (CDC) reported an increasing rate of autism in the United States. Can you explain why rates of autism are on the rise and whether there is a need for concern?

Earlier this year, the CDC reported that one in 31 (3.2%) children aged 8 years had a diagnosis of autism spectrum disorder (ASD), seemingly on the rise compared with 2023, when the reported rate was one in 36 children (2.8%). However, there is no need for concern. The United States is not experiencing an autism epidemic, nor is autism a new phenomenon.

Autism rates continue to rise because researchers and clinicians increasingly understand how to identify characteristics of ASD. Each year, we are improving pediatric screening for autism, making more referrals to experts for diagnosis and offering better services for very young children. These changes across different parts of the U.S. are reflected in the rising prevalence rates.

What does the existing body of research tell us about the causes of autism? Is there just one red flag or many possible explanations?

The vast majority of autism researchers understand that there is no one cause of autism. There are many possible causes of autism and contributing factors.

For decades, researchers across the country (and world) have studied the brain to decode differences in brain architecture and function that explain why some individuals are more genetically predisposed to autism. On top of that, we’ve identified hundreds of genes associated with autism, reviewed the environmental factors that may interact with genetic predisposition, and looked at how parental age (of both mothers and fathers) and illness during pregnancy (e.g., infections, chronic illness, depression) all contribute to autism, among other possible explanations.

Today we appreciate that autistic individuals have widely variable experiences with ASD. There is no one way to experience autism, and each individual will need support (or not) tailored to his or her needs and goals.

What kind of research needs to be conducted now and in the future to better understand autism and, potentially, identify management strategies?

We still have a good deal to learn about how genetic and environmental factors interact, and [need to] conduct further studies of brain development, especially in the early years. This kind of research will inform new approaches to how we can provide more personalized treatments and services to individuals with autism at all ages.

In April 2025, U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. announced that he would uncover the causes of autism by September. On September 22, 2025, President Donald Trump held a news conference about autism, which included Kennedy. They made statements suggesting a link between maternal use of Tylenol during pregnancy and possible use of folinic acid as a treatment for autism. What is your response to those claims?

Regarding Tylenol: Many long-term studies already investigated the possible association between Tylenol (acetaminophen) and autism. While a recent summary analysis found some evidence for a weak association, they did not evaluate the quality of the studies they reviewed. The most recent, rigorous study found that acetaminophen did not cause autism, when they controlled for genetic factors. These studies are difficult to conduct; the studies that do find an association do not always do a good job of separating out acetaminophen use from the reasons women use [it] in the first place. Given that use of acetaminophen during pregnancy has not increased over the past two decades alongside rates of autism, it’s clearly not related to the increase in prevalence rates.

Something else to consider is that these studies do not address the fact that fevers during pregnancy are known to increase risk for autism, and that’s why mothers take acetaminophen. The American College of Obstetricians and Gynecologists also asserts that there is no clear evidence that shows a direct relationship between the appropriate use of acetaminophen during pregnancy and adverse fetal development.

As always, women should consult their physician before using any medication during pregnancy, but acetaminophen is widely considered safe when used appropriately, and it is certainly the safest medication to take for pain, fever or infection.

Regarding folinic acid (leucovorin) as a treatment for autism: The evidence supporting folinic acid as a treatment for autism is still quite preliminary. There are five published clinical trials of leucovorin and autism, and all include a small group of participants.

The Coalition of Autism Scientists reviewed these studies and found that the researchers aren’t using high-quality study designs or statistical analyses. Most of these studies test many outcomes, without statistically adjusting for the fact that they are doing so along the way. Some of them use statistics that are inappropriate for a randomized trial (e.g., showing that there is statistically significant change in the intervention group but not in the control group, without actually comparing the groups). Others attempt to conduct analyses separately for children [who] they say have a gene or antibody that would suggest that they have folate deficiency, meaning that they are conducting the analysis on even smaller groups.

Bottom line: It is far too premature to recommend leucovorin as a treatment for autism.

In a published statement, the Coalition of Autism Scientists stated that “Secretary Kennedy’s announcement will cause confusion and fear. He seems to be cherry-picking old data rather than looking at the body of research as a whole.” Can you explain how Kennedy is cherry-picking and why that is problematic?

Secretary Kennedy is neither a doctor nor a researcher. He is a nonexpert with a well-publicized worldview that does not align with mainstream views about public health, vaccination or autism.

Out of all the factors that we know are associated with autism, genetics is by far the most significant yet. Secretary Kennedy has repeatedly dismissed the significance of genetic factors in contributing to risk for autism. There is strong evidence that several environmental factors are also important, but these too have been ignored by the secretary (e.g., parental age, maternal health, prematurity, air pollution). This is why we have characterized his approach as cherry-picking.

What should people understand about autism research?

There are thousands of researchers and clinicians around the world who have dedicated their careers to better understanding autism. We now have encyclopedic knowledge about the risk for autism, the experience of autism and its variable presentation in individuals. This body of research has resulted in increased local, state and national educational and interventional resources for autistic individuals.

Our goal is to support families and learn all that we can about autism. Hence, we will strive to continue this important work even it counters the information that is disseminated by the current administration.