Research from the Dean of Harvard's School of Public Health, Andrea A. Baccarelli, has become the center of a scientific and political debate regarding a potential link between prenatal acetaminophen use and autism. While government officials have cited his work to claim a direct cause, numerous experts assert the evidence only shows a correlation and that a causal link remains unproven. The discussion is further complicated by revelations that Baccarelli was paid over $150,000 to serve as an expert witness in litigation against the manufacturer of Tylenol.
Key Takeaways
- Dr. Andrea Baccarelli's research found an association between prenatal acetaminophen use and neurodevelopmental disorders.
- Trump administration officials cited this work to claim a "causal relationship," a conclusion not stated in the research itself.
- Multiple independent experts, including those from Princeton and Stanford, state that a causal link has not been established.
- In 2023, Baccarelli received at least $150,000 for expert testimony against Tylenol's manufacturer, prior to publishing his recent paper on the topic.
- A large-scale 2024 study involving 2.5 million children found no causal link between acetaminophen use and autism.
Research Enters Political Spotlight
The controversy escalated after Trump administration officials referenced Dr. Baccarelli's findings in public statements. During a press conference, Food and Drug Commissioner Marty A. Makary explicitly stated there is a "causal relationship between prenatal acetaminophen use and neurodevelopmental disorders of ADHD and autism spectrum disorder," attributing the idea to the Harvard dean.
This claim, however, appears to go beyond the conclusions of Baccarelli's own published work. His recent paper, a survey of 46 human studies published in August, concluded that prenatal acetaminophen use was associated with increased incidence of these disorders. His formal statement to the White House mentioned only the "possibility of a causal relationship" and emphasized the need for more research.
The public attention followed phone calls between Baccarelli, Health and Human Services Secretary Robert F. Kennedy Jr., and National Institutes of Health Director Jay Bhattacharya to discuss the research.
Distinguishing Correlation from Causation
In scientific research, correlation means two variables move together, but one does not necessarily cause the other. Causation means that a change in one variable is directly responsible for a change in another. Experts argue that while a correlation between acetaminophen use and autism may exist in some studies, a causal link has not been scientifically proven.
Experts Challenge Causation Claims
Several prominent scientists have pushed back against the assertion that acetaminophen causes autism, arguing the current evidence is insufficient and misinterpreted.
Samuel S. Wang, a professor of neuroscience at Princeton University, described the idea as, at best, a "massive overstatement and might be completely untrue." He noted that the underlying reasons for taking the drug during pregnancy could be confounding factors.
"Pregnant women take acetaminophen for a reason. They take it because they have a fever, or they have an infection or they are in pain, and these themselves are risk factors — potential risk factors — for autism," Wang explained.
This sentiment was shared by Dennis P. Wall, a professor at Stanford University, who stated, "There needs to be much more work done and additional studies to be able to identify causal mechanisms. That simply hasn’t been done."
Major Study Finds No Causal Link
A significant counterpoint to the causation theory comes from a 2024 study published in the Journal of the American Medical Association (JAMA). The extensive research, which analyzed data from 2.5 million children born in Sweden, controlled for numerous variables and found no evidence of a causal relationship between acetaminophen consumption during pregnancy and the incidence of autism.
What Causes Autism?
According to the scientific consensus, autism spectrum disorder is believed to be caused by a combination of factors, including: genetic inheritance, specific combinations of genes, environmental influences, and biological stresses during mid-to-late pregnancy. A single cause has not been identified.
Role as a Paid Expert Witness
Adding another layer to the story, court documents reveal Dr. Baccarelli's financial involvement in legal proceedings related to the drug. In 2023, while he was a professor at Columbia University, Baccarelli was paid as an expert witness for plaintiffs in a lawsuit against Tylenol's manufacturer.
According to a deposition from that year, he was compensated at a rate of $700 per hour. "I work for more than 200 hours, so it’s about $150,000," Baccarelli stated in the deposition. His work on the case culminated around the time of the deposition.
A spokesperson for the Harvard School of Public Health confirmed to the New York Times that Baccarelli's testimony in the deposition was accurate. The judge in the case wrote that Baccarelli had "cherry-picked and misrepresented study results," though the plaintiffs have appealed that decision.
Catherine E. Lord, a professor at the University of California, Los Angeles, commented that it is not uncommon for medical professionals to be paid for such testimony. However, she suggested that Baccarelli's willingness to testify indicates he is "invested in finding something more than most of us would be." Lord also called the leap from correlation to causation "really irresponsible."
