LEILA FADEL, HOST:
Coming up, we've got the director of a research institute who has studied autism for five decades. We'll ask her to draw on her expertise to unpack the president's claim that the active ingredient in Tylenol is linked to autism.
MICHEL MARTIN, HOST:
First, though, as President Trump warns pregnant women to avoid the drug, science does not back up his certainty.
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PRESIDENT DONALD TRUMP: And you shouldn't take it during the entire pregnancy. They may tell you that toward the end of the pregnancy. You shouldn't take it during the entire. And you shouldn't give the child the Tylenol every time he goes - he's born and he goes and has a shot.
MARTIN: The president also suggested that a cancer drug might relieve some symptoms of autism, and he repeated a favorite talking point that vaccines are harming children.
FADEL: Joining me now to break down the president's advice is NPR science correspondent Jon Hamilton, who's with me in the studio. Good morning, Jon.
JON HAMILTON, BYLINE: Good morning to you.
FADEL: So first, exactly how does the president expect to get people to go along with these recommendations?
HAMILTON: Largely through changing the labels on these drugs and also changing payment policies. So for acetaminophen - that's the active ingredient in Tylenol - Trump said the Food and Drug Administration will now require the label to warn pregnant women about a risk of autism. The FDA, however, later issued a statement that was a bit less strident than the president's remarks that we just heard. It says the pain drug may be associated with an increased risk, and it said it was reasonable for pregnant women to take acetaminophen in certain scenarios. As for the cancer drug, which is a form of vitamin B, the label will now list autism as one of the approved uses, and Trump says Medicaid will now cover it for this purpose. It is worth noting that there has been no formal process for any of this, like an FDA hearing, and they are making the labeling changes anyway.
FADEL: OK. So we heard that the science doesn't back it up. There's been no formal process. So to say the least, this is controversial advice. Is there good science at all supporting either of these recommendations?
HAMILTON: Well, let's start with the cancer drug, which is called leucovorin, or folinic acid. And it seems to help get a form of vitamin B into the brain, but it's not clear how many people with autism actually have a deficiency of that vitamin in their brains. And there are really only anecdotal reports that the drug reduces the symptoms of autism.
FADEL: And what about Tylenol?
HAMILTON: There is some evidence, but it's not the sort that federal agencies usually require before making recommendation.
FADEL: OK.
HAMILTON: The government likes a randomized controlled trial studying - something showing cause and effect. What they've got here is some studies of pregnant women that found a potential association between taking acetaminophen during pregnancy and an increased likelihood that a child would later be diagnosed with autism spectrum disorder. Other studies, though, have not found this association. And the reason for these inconsistent results may have to do with a person's genes, which are far and away the most powerful predictor of autism. I spoke with Jonathan Sebat. He's a professor of psychiatry at the University of California, San Diego.
JONATHAN SEBAT: There have been a number of more recent studies of acetaminophen that actually account for familial genetic factors, so they look at siblings and other first-degree relatives. And when you do that, the correlation with acetaminophen really weakens.
FADEL: Are there any credible scientists, Jon, who think Tylenol might contribute to autism?
HAMILTON: There are some, but they generally disagree with Trump on vaccines. And they are a lot more measured in how they express the risk from acetaminophen.
FADEL: OK.
HAMILTON: I spoke with Ann Bauer, an epidemiologist at the University of Massachusetts.
ANN BAUER: The case is closed on vaccines. The case is still open on acetaminophen.
HAMILTON: Now, Bauer says women should know about the potential risk, but she says they should also know that there is still a lot of uncertainty about that risk.
FADEL: NPR health correspondent Jon Hamilton. Thank you, Jon.
HAMILTON: You're welcome. Transcript provided by NPR, Copyright NPR.
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