What We’re Learning (and Still Don’t Know) About Autism, Tylenol, Folic Acid, and Vaccines

There’s been a lot of buzz lately about a new research review from Harvard that’s raised

questions about whether taking Tylenol during pregnancy could increase the risk of autism in children. The topic is sensitive, complicated, and full of strong opinions — so let’s walk through what the study actually found, what it didn’t, and what other recent research is saying about possible links to autism, including folic acid and vaccines.

The Tylenol Study: What Did Harvard Researchers Find?

A group of researchers from Harvard, Mount Sinai, and other institutions recently reviewed dozens of studies that looked at whether pregnant women who took acetaminophen (the active ingredient in Tylenol) were more likely to have children diagnosed with autism or ADHD. They analyzed 46 studies in total and found that more than half reported a possible connection.

But — and this is important — the review doesn’t prove that Tylenol causes autism. The researchers were careful to say that the findings show an “association,” which just means the two things happened together in some studies. It doesn’t mean one caused the other. For example, people who take Tylenol during pregnancy often do so because they’re sick or have a fever — and we already know that infections and inflammation during pregnancy can play a role in brain development.

Also worth noting: one of the largest and best-designed studies on this topic, done in Sweden, looked at over 2 million children and found no link between Tylenol use and autism when comparing siblings — meaning when one child was exposed and the other wasn’t. That kind of study helps control for family and genetic factors, and it found no cause for concern.

So, while the Harvard review is getting a lot of attention, many experts say it’s too early to change how we use Tylenol during pregnancy. The current advice is to use it only when needed, at the lowest dose and for the shortest time — but not to panic or avoid it entirely.

What About Folic Acid and Autism?

On the flip side, there’s also been encouraging research about folic acid — a B vitamin found in many prenatal vitamins and fortified foods — and its possible protective effect against autism. Some studies suggest that women who take folic acid before and during early pregnancy may be less likely to have a child diagnosed with autism.

One study even showed that moms who took the recommended daily amount of folic acid had around a 40 to 45 percent lower chance of having a child with autism. That’s a big number, and it’s backed up by multiple other studies. While not all results are perfectly consistent, most researchers agree that folic acid plays a helpful role in brain development.

There’s also newer research exploring whether some children with autism have trouble using folate in their bodies due to certain antibodies. In those cases, a special form of folate called folinic acid has been tested in small trials. Some parents have reported improvements in speech and social behavior after their children took it, though the studies are still early and more research is needed.

One thing to keep in mind is that too much folic acid — especially in people with certain genetic traits — could possibly have downsides, though this is still being studied. For now, health experts continue to recommend that women who are pregnant or trying to conceive take the standard prenatal vitamin amount, as it’s already known to prevent serious birth defects like spina bifida.

The Vaccine Question — Again?

Vaccines and autism have been linked in public debate for more than 20 years, even though

study after study has found no connection. That hasn’t stopped the topic from popping back up — especially now that some public health officials in the U.S. are reopening the discussion and asking for more research.

To be clear, this doesn’t mean there’s new evidence showing vaccines cause autism. In fact, the largest studies — including one that followed over a million children — have shown no link between vaccines and autism, ADHD, asthma, or other health issues. Major health organizations around the world still say vaccines are safe and do not cause autism.

But because vaccine hesitancy is already a growing issue, some experts worry that bringing this debate back without solid new findings could do more harm than good by creating more fear and confusion.

So What’s the Bottom Line?

Autism is incredibly complex. It’s not caused by any single thing. In fact, researchers believe that a combination of genetic and environmental factors likely shape how the brain develops. And what might affect one child may not have the same effect on another — which is why studying autism is so challenging.

The recent Harvard review on Tylenol raises important questions, but it doesn’t give clear answers. Other studies, including some very large ones, don’t support a strong link. Folic acid continues to look promising for prevention, and there’s early hope for treatments using special forms like folinic acid — but we’re not there yet in terms of wide clinical use. And when it comes to vaccines, there is still no credible scientific evidence connecting them to autism.

If you’re pregnant or planning to become pregnant, the best advice is to talk with your doctor. Ask questions, weigh the risks and benefits, and make decisions based on the full picture — not just headlines or social media posts.

The science around autism is still unfolding, and it’s okay to want clear answers. But sometimes, the most honest thing science can say is: “We’re still learning.”