Or you may have heard about the notorious Pokemon epilepsy scare, in which blinking lights in an episode of the cartoon triggered nausea and vomiting in hundreds of Japanese kids. The original reported cases might have been real, but in the end, the number of kids reporting attacks was many times greater than the actual portion of the population that has sensitivity to flashing lights. At some point, healthy kids started convincing themselves they were having the seizures.
"Y-y-yeah, th-this is how J-j-japan enjoys th-things. You w-wouldn't understand."
Of course, it would be different if we were talking about symptoms like, say, blood shooting from your eyes -- it's hard for your body to spontaneously cause that due to peer pressure. But we all know that certain symptoms can be caused by a fear or stress reaction -- nausea, headaches, dizziness, hives -- and if the thing you're scared of supposedly causes those symptoms, you've got all of the makings of a very imaginary yet real disease. And it gets weirder ...