I am aware of the Batman as a Inmate of Arkham fan theory, sometimes called the Villain fan theory or Bruce Wayne crazy theory, has been around for around 10 years.
This theory states than Bruce Wayne is a patient of Arkham Asylum and all of Batman's enemies are other patients or doctors and are all a part of Bruce Wayne's psychosis.
Has this fan theory or a similar concept with the Batman character ever been made into an official or unofficial comic book, novel, web comic or other type of media, which fleshes out the story.
I'm looking for something that is more than just a Reddit or Blog post about the theory and has a narrative story around the idea.