I know a fellow who was seriously considering joning an Orthodox monastery (he's Catholic) partially because he hated the side effects of the anti-psychotics so much, and partially because he liked the voice he was "hearing"; his "symptom" is hearing the BVM speak to him.
He's switched drugs now, is doing OK.
I assume that since the medication stops it, he's not "really" hearing the BVM.
No, I've never had any such experience.
Christianity does recognize that there are imposters and substitutions. It may be difficult in some cases to distinguish the two. But the diffulty (or your example) merely illustrates that there are two causes. In this case it's easy to see one significant difference: one requires medication.