After President Donald Trump’s September 2025 unsupported claim that autism is linked to the use of acetaminophen (Tylenol) in pregnancy and that leucovorin may help autistic children, US Tylenol use fell among pregnant women, while leucovorin (folinic acid) prescriptions surged, Harvard and Brown University physician researchers suggested yesterday in The Lancet.
Despite the lack of new evidence, Trump made those statements at a White House briefing, where he called leucovorin “an exciting therapy that may benefit large numbers of children who have suffered from autism,” which was followed by a US Food and Drug Administration (FDA) label update listing it as a potential treatment for cerebral folate deficiency, a rare neurologic syndrome.
“The problem is that the best science does not suggest this linkage between acetaminophen use and later rates of autism,” first author Jeremy Faust, MD, of Harvard Medical School, wrote on his Inside Medicine Substack yesterday. “In the case of leucovorin, a drug that can treat a condition called cerebral folate deficiency, there is simply no good evidence to suggest that it will help most children with autism or related conditions.”
The authors caution that a causal relationship can’t be established with observational studies.
Models projected counterfactual scenarios
The researchers analyzed Epic electronic health record data up to November 2025 for Tylenol orders during emergency department (ED) visits and new leucovorin prescriptions in outpatient clinical visits. They also conducted an interrupted time-series analysis using weekly ED orders or outpatient clinic prescription counts from before Trump’s claims (June 30 to September 21, 2025).
The team then used the models to project counterfactual scenarios, predicting expected orders and prescription numbers for the post-policy period had the briefing not occurred. They also assessed orders for Tylenol, as well as opioids and lactated Ringer's solution as control comparators. The analysis was repeated for non-pregnant women of the same age.
Children aged 5 to 17 years were used in the leucovorin analysis using new outpatient prescriptions for leucovorin, as well as aripiprazole, risperidone (the only other drugs with FDA-approved indications for use in autism spectrum disorder), folic acid preparations, and levoleucovorin (based on their similarity to leucovorin) as control comparators. The levoleucovorin analysis, however, was abandoned due to insufficient data.
Without evidence, politicians steer health behavior
From Sept 22, 2025, to November 2025, pregnant women aged 15 to 44 years made 88,857 ED visits, while non-pregnant women made 853,216 such visits, and children aged five to 17 years had more than 8.6 million outpatient visits.
