Not the OP, but there's an odd theory from the early days of psychiatry which theorises that extreme anxiety is a protection against psychosis, basically a protective mechanism in the brain almost equivalent to a scram on a nuclear reactor. If that anxiety barrier is broken through, then it can be psychosis, and it may be that the barrier is metaphysical.

Terrifies me a bit because I've been to that barrier, not by choice, avoided psychosis, but got close enough to the edge that I still shudder at the memories...