Thus, the cause of the disease chorea lasciva is a mere opinion and idea, assumed by imagination, affecting those who believe in such a thing. This opinion and idea are the origin of the disease both in children and adults. In children the case is also imagination, based not on thinking but on perceiving, because they have heard or seen something. The reason is this: their sight and hearing are so strong that unconsciously they have fantasies about what they have seen or heard.
Paracelsus, Von den Krankeiten, 1567