There is one additional thing that came to mind after I finished my last post to your Thread, Rh01. As I indicated, I personally tend to believe that the impetus for this sort of thing is probably hard-wired into a person's brain.

One thing that has happened with me regarding compulsive behaviors is that, when I would manage to stop doing one thing, I would discover something else. For example, growing up I bit my fingernails. When I became a young adult & became concerned about my appearance, I managed to break myself of nail biting. Then I discovered hair pulling. And there have been other things. I've heard this from others who struggle with mental health issues as well.

So even if you can manage to figure out a way to get your son to stop wearing diapers & in other ways wanting to revert to being a baby, my experience suggests to me there is a strong likelihood what now drives him to wear diapers will simply find another avenue for expression. For example, he could begin cutting or become anorexic / bulimic.

I apologize if I'm continuing to heap additional concerns on you with regard to this. It is a difficult problem. My best wishes to you all.