Fellow atheists/agnostics, what do you think of this?

I recently had a conversation with the youth pastor of my parents' church. The youth pastor told me that he had once witnessed a demon possession. Everything he told me simply sounded like multiple personality disorder, but then he brought up "incredible strength." Since he was telling me an anecdote, I could not tell if he was deluded, exaggerating, or just plain lying. But i'm curious to know, this "incredible strength" he mentioned, if it is indeed a part of multiple personality disorder, is it rather just an adrenaline rush due to high anxiety?