“Let’s take this back a couple hundred years,” said Brian Southwell, the director of the “Science in the Public Sphere” program at the Center for Communication Science at RTI International. “There was an ongoing debate between a couple guys in Europe: Spinoza and Descartes.”

These two philosophers were debating, essentially, about whether people are able to readily identify fake news.

“Descartes had a lot of optimism about our ability to screen out information that is false,” Southwell said Saturday at the Aspen Ideas Festival, which is co-hosted by the Aspen Institute and The Atlantic. “Spinoza said we accept information wholesale and then with a different part of our brain we tag it as being false or true. That system works fine, but it leaves the door open for distraction, for fatigue, for other things that might get in the way. Recent decades have provided empirical support for the Spinoza account.”

Recent years—this past year in particular—have shown beyond a shadow of a doubt that, despite Descartes’ faith, people are susceptible to false information and fake news. And while many of the fake news stories that have gotten the most attention had to do with the 2016 U.S. presidential election, fake news about health seems to be more pervasive and harder to weed out.

“My sense is that of all the categories of fake news, health news is the worst. There’s more bad health news out there than there is in any other category,” said Kelly McBride, the vice president of the Poynter Institute. And “reliable sources on other topics are [sometimes] really bad on health care news.”

This includes not just deliberately misleading stories, like the ones about that mom from who-knows-where who’s discovered all those secrets—for weight loss, for teeth whitening, for reversing wrinkles—that doctors don’t want you to know about, but also what Joanne Kenen, the executive editor for health care at Politico, calls “junk news.”

“The junk news would be… how many coffee studies have we read that all say something different?” Kenen asked. “If you’re a PR department that really wants to get your study read, you would say ‘Chocolate and Coffee Guarantee Great Sex Until You’re 80.’ You would break your server.”

PR departments and the researchers they serve are a little bit to blame for the problem, for hyping up studies like that, McBride said. But journalists are to blame as well, for taking the bait, and for doing their own hyping to get those sweet sweet clicks. Even if they don’t hype—even if they responsibly cover a study done in mice, say, and clarify that it’s just in mice, and don’t say it means anything more than it does, readers might ascribe an outsized importance to that study just because the journalist chose to highlight it at all.  “Everybody has a role in this,” McBride said.

If health is indeed the worst subject for fake news, it’s because it’s got a few things working against it. It’s not just that the current journalism environment rewards quick, numerous, clicky stories—that’s true for all subjects. But it creates additional problems for science news because “the cycle of journalism and the cycle of science are completely incompatible,” McBride said. The scientific process takes a long time, which means new developments happen very slowly. “In science, good information is really boring. Science doesn’t leap ahead the way journalists like to cover it,” McBride said.

In fact, the slow nature of science is sometimes used against it. Science takes a long time to answer questions; findings get refuted; the accepted wisdom changes. And some climate change deniers and vaccination skeptics have started sowing doubt by saying the science on these issues is unsettled, that there are still open questions we have to investigate.

And within the broad realm of science, health science may be an easier domain for misinformation to flourish. “I think it’s fair to say we are differentially vulnerable to misleading news depending on the topic,” Southwell said. “Health in general tends to be very personal for people.” Information—and misinformation—about your well-being is likely to feel more high-stakes than information about the business world, or celebrities.

“We’re in a democracy that relies heavily on the marketplace of ideas,” McBride said. “The idea is that the ideas will compete and the audience will figure out what the best ones are. If most of the information is bad—even if 51 percent of it is bad—the audience will begin to distrust the marketplace.” And we already know that trust in the media—where a lot of these ideas are disseminated—is at an all-time low.

McBride suspects health news may be at just such a tipping point of bad information. “It’s dramatically weakened,” she said, “to the point where I’m not sure I would tell anyone to rely on the marketplace of ideas for information—which is really dangerous when it comes to healthcare.”