Visitors who have some religious faith, do not be put off by the post title: it bears on a much narrower and more realistic matter than it may imply. Not only are you welcome here, you probably have the most important things to say.
I am curious: in America, one of the stereotypes of madness we on the outside of mental hospitals used to hold was of the fellow who was convinced that he was god or alternatively, Jesus. Claim that too loudly and they came after you with a straight jacket. It was funny not because it was crazy but because it was scary. "They'll lock you up next to Napoleon!" Jim Jones was arguably one of these crazies but David Koresh was not.
It is probably a lot harder to come by an accurate census of what the most common delusions are these days. Chlorpromazine and its descendants have emptied the state mental hospitals onto the streets and homeless shelters. The census I really want will never be taken, probably is impossible to gather meaningfully. In countries where Christianity is not the dominant religion and where someone who states that he is the deity is not promptly run thSave as Draftrough with a sword, what are the varieties of religious delusion? Did a Hindu pantheon rant behind the bars of an asylum in New Delhi? Were the funny farms of Tibet full of dishevelled Buddhas and the wards in Canton inhabited by assorted people claiming they were Confucius? I know its insensitive, macabre and Thurberesque, but as data, I think it would be interesting.
[my apology for calving a this post out of its predecessor but that first post wanted thematic cohesiveness and this quest, as I hope will become a pattern, raises a question in a narrow context, suitable for a bounded discussion on the topic of kinds of belief or at least, of believing]