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During a press briefing on Monday, President Trump revealed that his administration was taking steps to tackle “the rapid increase in autism.” He insinuated that childhood vaccinations and acetaminophen, the active component in Tylenol, are responsible for the growing incidence and advised expecting mothers to avoid the medication. “Don’t use Tylenol,” he declared. “Strive fiercely to refrain from it.”
The president’s claims left numerous scientists and health experts baffled and concerned. The idea that childhood vaccines lead to autism has been thoroughly disproven.
“Countless studies involving numerous children have led scientists to rule out vaccines as a major causal factor in autism,” states James McPartland, a child psychologist and director of the Yale Center for Brain and Mind Health in New Haven, Connecticut.
And while some research indicates a connection between Tylenol and autism, the most rigorous studies have not established a correlation.
The administration also declared that the Food and Drug Administration will strive to make a drug known as leucovorin available as a treatment for children with autism. Some preliminary studies indicate the drug may hold promise, but “these are among the most initial treatment studies we possess,” remarks Matthew Lerner, a psychologist at Drexel University’s A.J. Drexel Autism Institute in Philadelphia. “This isn’t one I would assert the research suggests is prepared for expedited approval.”
The press briefing “concerns us researchers who have dedicated our entire professions to deeper understanding of autism,” stated the Coalition for Autism Researchers, a collective of over 250 scientists, in a statement.
“The data referenced do not support the assertion that Tylenol induces autism and that leucovorin serves as a cure, and they merely incite fear and inaccurately imply hope when no straightforward solution exists.”
There’s much to analyze here. Let’s start.
Has there been a “rapid increase” in autism?
Not in the manner the president suggested. Indeed, the prevalence of autism has escalated, changing from approximately 1 in 500 children in 1995 to 1 in 31 today. However, this is largely attributed to changes in diagnosis criteria. The most recent revision of the Diagnostic and Statistical Manual of Mental Disorders, released in 2013, combined five formerly distinct diagnoses into a unified diagnosis of autism spectrum disorder (ASD).
This adjustment meant that a greater number of individuals qualified for an autism diagnosis. Lerner notes that awareness of the condition has also greatly increased compared to several decades past. “There’s autism visibility in the media,” he states. “Numerous notable individuals from various sectors such as news, finance, business, and Hollywood are openly autistic.”
Is Tylenol a factor in autism?
Some research has discovered a correlation between acetaminophen use during pregnancy and autism in offspring. In these studies, researchers inquired about women’s past acetaminophen consumption during pregnancy and then analyzed whether children of mothers who used the medication were more likely to develop autism compared to children of mothers who did not.
These kinds of epidemiological studies can be difficult to interpret due to potential biases. For instance, women taking acetaminophen during pregnancy might do so because of an infection, fever, or an autoimmune condition.
“Many of these factors could themselves contribute to autism,” asserts Ian Douglas, an epidemiologist at the London School of Hygiene and Tropical Medicine. Additionally, it’s feasible that women with a heightened genetic susceptibility to autism might have other health issues that make them more inclined to use acetaminophen.
Two studies endeavored to account for these potential biases by examining siblings whose mothers had used acetaminophen in just one of the pregnancies. The largest is a 2024 study that investigated nearly 2.5 million children born between 1915 and 2019 in Sweden. The researchers initially identified a slight increase in autism and ADHD risk among the children whose mothers took acetaminophen, but upon conducting a sibling analysis, the correlation vanished.
Conversely, scientists have long understood that autism is predominantly genetic. Twin studies indicate that 60% to 90% of autism risk can be attributed to genetics. However, environmental factors seem to play a role as well. This “doesn’t necessarily imply toxins in the environment,” Lerner states. In fact, one of the strongest environmental predictors of autism is father’s age, with autism rates appearing to be elevated when a father is over 40 years old.
So should pregnant individuals refrain from Tylenol just to be safe?
No. Acetaminophen is the only over-the-counter pain reliever deemed safe to use during pregnancy, and women should utilize it when necessary. The American College of Obstetricians and Gynecologists (ACOG) endorses acetaminophen use in pregnancy “when taken as needed, in moderation, and after consulting with a physician.”
“There’s no disadvantage in not taking it,” Trump asserted at the press conference. However, elevated fevers during pregnancy can pose risks. “The conditions prompting people to use acetaminophen during pregnancy are considerably more hazardous than any theoretical concerns and can lead to severe illness and mortality for the mother and fetus,” said ACOG President Steven Fleischman in a statement.
What about this novel treatment for autism? Is it effective?
The medication is known as leucovorin. It is also referred to as folinic acid; similar to folic acid, it is a variety of folate, a B vitamin present in leafy vegetables and legumes. The drug has been utilized for years to mitigate the side effects of certain cancer therapies and as a remedy for anemia.
Researchers have recognized for decades that folate is crucial for the fetal growth of the brain and spine. Women lacking adequate folate during pregnancy face an increased risk of birthing babies with neural tube defects such as spina bifida. Consequently, many foods are fortified with folic acid, and the CDC advises women to consume folic acid supplements during pregnancy. “If you are pregnant and taking maternal prenatal vitamins, there’s a good chance it contains folate already,” Lerner remarks.
“The notion that a significant number of autistic individuals have autism due to folate-related issues is not a well-founded or broadly accepted idea,” states McPartland.
Nonetheless, in the early 2000s, researchers in Germany identified a small collection of children who exhibited neurodevelopmental symptoms due to a folate deficiency. “These children are typically born healthy at birth,” explains Edward Quadros, a biologist at SUNY Downstate Health Sciences University in Brooklyn, New York. However, after a year or two, “they start to manifest neurological symptoms very akin to autism,” he continues. When these children were administered folinic acid, some of their symptoms improved, particularly in those younger than six years old.
Because these children exhibited low folate levels in the fluid surrounding the spine and brain but normal levels in the blood, researchers theorized that the issue stemmed from impaired transport of folate from the bloodstream to that fluid. Research by Quadros and other scientists indicated that the deficiency was triggered by an autoimmune response. Children produce antibodies against the receptors responsible for folate transport, which block folate from crossing the blood-brain barrier. High doses of folinic acid, however, activate a secondary transporter that permits folate entry, says Quadros.
A multitude of individual anecdotal cases suggest that leucovorin is effective. However, the medication has only been evaluated as a treatment for autism in four limited trials that utilized varying dosages and assessed different outcomes. The evidence supporting its ability to enhance autism symptoms is “weak,” according to the Coalition of Autism Scientists. “A significantly higher standard of research is necessary to ascertain whether leucovorin is a viable and safe autism treatment,” the researchers stated in a press release.
