When I was a kid, someone told me that running a fan too close to my face was dangerous to my health, and I’ve kind of believed it ever since. For the 20-some years since, I’ve assumed that person was one of my parents, but when I mentioned this to them recently, neither had any idea what I was talking about. “That doesn’t sound like something I’d believe,” my dad said, and he’s right, it doesn’t. But I know someone in my home once told me to move my fan further away from my bed so I wouldn’t get sick overnight, and if it wasn’t my parents, then who was it? My best guess at this time is a paranoid babysitter. No matter that I never encountered any substantiating evidence; the idea of a fan’s concentrated breeze making me sick held enough intuitive sway in my childhood psyche that it stuck there. Even though I know now that it isn’t exactly true, I wonder if there’s something to the idea—it had to come from somewhere. Right?

In fact, many cultures across the globe have their own stories of wind-based illnesses, says Frank Bures, author of The Geography of Madness. In his book, Bures writes that some ancient Chinese medical texts warned readers of “wind insanity” and even “wind stupidity.” Variations on these beliefs persist today, too; in Italy, people wear scarves around their necks to protect against colpo d’aria (a hit of air), and in the Czech Republic, some people fear the wind from air conditioners and refrigerators, believing they cause rheumatism, among other health issues. Most (if not all) Americans have been told not to go outside with wet hair lest we “catch a chill”—a belief in a cause-and-effect model with little scientific backing. Perhaps the most extreme form of these supposed illnesses can be found in Korea, where they call it something else: fan death, or the belief that running a fan in an enclosed room will actually kill you.

Fears about electric fans in Korea seem to date back as early as 1927, when a story called “Strange Harm From Electric Fans” was printed in Jungoe Ilbo (“Domestic and International Daily”), warning readers that the new technology came with a risk of nausea, facial paralysis, and even asphyxiation—the theory there being that the fan’s circulation of stale air causes its user to choke on their own carbon dioxide. Fifty or so years later, Bures tells me, a Korean man was reportedly found dead in his room, the windows and doors shut, with two electric fans running. Bures attributes the prominence of the modern fan-death myth to this case. Ever since, stories of supposed “fan deaths” have appeared regularly in South Korean news sources, particularly in the summer months. “That's how these things usually go,” says Bures. “You can't necessarily prove that the wind killed the person, and in a way it doesn't matter, because everyone believes it's the fan.” Some suggest the fan death myth was even propagated by the South Korean government to curb the use of electricity during the 1970s energy crisis.

The specific root (or roots) of the widespread belief are difficult to pinpoint, says Bures, but what matters most, in his view, is the way that belief in fan death and other impossible conditions like it—which he calls “cultural syndromes”—self-perpetuates.

“The only way something like that can spread is if people believe in the cause at the root of it. If you believe that wind can have this harmful effect, or something about an electric fan can, then it can spread,” says Bures. “If nobody believes it, then it won't spread.” Fan death may not make much sense to those of us living outside Korea, but the chemtrail conspiracy probably doesn’t make much sense to people living outside the United States (and, more specifically, Hollywood), either. The threats and specters may vary from culture to culture and country to country, but what unites them is the strength of people’s belief in them, even in the near-total absence of evidence. In his book, Bures writes, “Hearing about a cultural syndrome was one of the primary risk factors.” In that sense, certain cultural syndromes can be made “real” by our belief in them — a phenomenon called the “nocebo effect,” where negative expectations can start a chain of harmful events which ultimately fulfill those expectations.

While it remains extremely unlikely that believing a fan can kill you will directly cause that fan to kill you, and the potency of the nocebo effect depends on a number of contextual factors, there is evidence to suggest that belief in one’s potential to experience a given medical crisis makes a person more susceptible to it. “If you read the side effects on a medicine, you're more likely to experience those side effects,” says Bures. “In a randomized clinical trial, researchers will warn people about the side effects of a drug or treatment, and people in the placebo group will sometimes have to drop out because their side effects are so severe.” As a mild hypochondriac, this seems terribly unfair to me. One would think the constant worrying was punishment enough.

But as long as the credulity is there, so will be the possibility of fan death — not because our electric fans are actually asphyxiating us, but because enough people believe they could. As for me, I still keep my own fan at least three feet away from the bed. I don’t necessarily think setting it up closer would make me sick, but I don’t particularly want to find out for sure, either.