The creators of the DSM have become extremely wary of creating diagnoses on people who don't think they have a problem, and who function in their everyday lives

The creators of the DSM have become extremely wary of creating diagnoses on people who don't think they have a problem, and who function in their everyday lives. I don't think there's anything particular about religion that can be classed as a distinct disorder. There's psychosis(schizophrenia, type 1 bipolar disorder, schizoaffective disorder), etc and delusional disorder for cases where people lose their grip on reality completely, and become a danger to themselves and others. The criteria for a belief to be a delusion are pretty strict. For it to be a delusion the person would have to hold on to their belief despite irrefutable evidence to the contrary. Religious belief is in most cases something completely different, namely a strongly held conviction that's been drilled in since birth. And religious beliefs are designed to be hard to disprove. So it's like trying to remove the bottom piece of a jenga tower. But it's not usually a sign of some profound defect in cognition, which a delusion is. Of course psychotic delusions often can take on religious content, but that's perfectly within the existing criteria for the various psychotic/delusional disorders. It's just that the bar for describing a religious belief as a delusion is quite high, because perfectly healthy, functional people regularly believe some pretty "out there" stuff.