After a White House autism briefing, acetaminophen prescriptions dropped 20% and leucovorin surged 93%

Published in The Lancet. Brown University and Mass General Brigham.

On September 22, 2025, the White House held a briefing about autism. Administration officials, including the president and the head of the FDA, claimed that acetaminophen use during pregnancy might increase autism risk and suggested that leucovorin, a folate-based drug approved for certain cancer and metabolic conditions, could treat autism in children. No new clinical trial data supported either claim. No medical guidelines had changed.

Within weeks, prescribing patterns across the United States shifted dramatically.

The numbers from 1,600 hospitals

Researchers from Brown University's School of Public Health and Mass General Brigham tracked what happened next using Cosmos, an electronic health record database covering more than 1,600 hospitals and 37,000 clinics nationwide. They compared weekly prescribing trends before and after the briefing against expected levels based on prior patterns.

Acetaminophen orders for pregnant women in emergency rooms dropped about 10% overall compared with expected trends. In the first month, the decline was 16%. At its steepest, in the third week after the briefing, prescribing fell 20% below predicted levels.

The leucovorin numbers moved in the opposite direction. Outpatient prescriptions for children ages 5 to 17 increased approximately 71% above expected levels. During the first month, they were up 93%. In the second week, prescribing more than doubled. About 72% of these prescriptions were written for children with autism diagnoses, a group that represents only 4% of the pediatric population in the dataset.

No new evidence, just a press conference

The changes were specific to the two drugs mentioned in the briefing. They did not reflect a broader shift in prescribing behavior, which makes the association with the announcement harder to dismiss as coincidence. The study, published in The Lancet, describes the timing as consistent with a causal link, though its observational design cannot prove causation definitively.

Leucovorin has been studied in small clinical trials for autism, but the results have been mixed and preliminary. It is not part of standard autism treatment guidelines. The evidence base for avoiding acetaminophen in pregnancy to prevent autism is similarly thin. Major medical organizations have not recommended against its use for that purpose.

"The White House briefing was an extremely unusual mechanism to communicate medical information and bypassed many standard checks on ensuring accurate messaging," said study author Dr. Michael Barnett, a physician and professor at Brown. "The results show just how much political leaders can steer health behavior even when there has been no change in the evidence for these therapies."

Doctors responded too

An important dimension of the findings is that these were not just consumer decisions. Leucovorin is a prescription medication. The surge in prescribing means physicians were writing these orders, either because they were influenced by the briefing themselves or because parents requested the drug and doctors complied.

"An important implication of these results is also that it's not just patients who were influenced by the unconventional press conference," Barnett said. "Their doctors were either influenced themselves or pushed by patients to adopt a new practice."

Acetaminophen orders in emergency rooms are typically physician-driven decisions, suggesting the briefing influenced clinical judgment directly, not just patient demand.

What the study does not show

The analysis does not assess whether patients experienced better or worse outcomes as a result of these prescribing changes. If pregnant women in pain avoided acetaminophen, we do not know what they used instead, or whether the substitution carried its own risks. If children with autism received leucovorin, we do not know whether it helped, hurt, or made no difference.

The study also cannot determine how long the prescribing shifts persisted beyond the observation window, or whether they have since reverted to baseline.

"It can take years, even decades, for high-quality research to finally reach clinicians," said study co-author Dr. Jeremy Samuel Faust, an emergency physician at Brigham and Women's Hospital. "Here, by using the White House, it was done overnight."

The speed of uptake is the finding that should concern anyone involved in medical evidence translation. A single political announcement, without peer-reviewed evidence, formal guideline changes, or regulatory action, moved prescribing behavior across thousands of hospitals in a matter of weeks. The mechanisms that normally gate medical practice, evidence review, guideline committees, continuing education, were bypassed entirely.