Reification

You don't need to take drugs to hallucinate; improper language can fill your world with phantoms and spooks of many kinds.

I've been looking for a while for a word for the simple error of imagining that something exists just because there is a word or phrase for it; I'm pretty sure that almost every syndrome we're nagged about will turn out to be a chimera and bemuse generations to come.

Reification, the treatement of an abstraction (abstract belief or hypothetical construct) as if it were a concrete, real event, or physical entity, is close, but I'm not entirely sure it is on the money.