Group hysteria, academically also known as "collective hysteria," "mass psychogenic illness," or "collective psychogenic illness," refers to a phenomenon where physiological or psychological symptoms rapidly spread within a social group.
Its core symptom is: A group of people simultaneously exhibiting similar physical or mental symptoms, yet no organic or physiological cause can be identified for these symptoms.
Simply put, "group hysteria" is a "psychological contagious disease." The root of the issue lies in psychological and social factors, rather than viruses, toxins, or bacteria.
Historically, there have been many famous cases of "group hysteria."
