H_James said:
There's an excellent* Colin Wilson book about people with messiah complexes. One of the stories involved a psychiatrist treating a deeply delusional patient - using a certainly avant-garde method, in which he entered into the delusion. After a while, the patient was apparently 'cured', whereas the psychiatrist had a hard time convincing himself that all the stuff about empires on mars etc was in fact not true.
*With all the usual qualifications
that comes from an essay, "The Jet-Propelled Couch" from
The Fifty-Minute Hour by Robert Lindner. Lindner also wrote
Rebel Without a Cause, the book that they adapted into the the movie with James Dean.
Lindner has a client who works for a high level military secret research project. who has the same name as the main character in a science fiction stories. he begins to convince himself that the stories do describe his real life as a powerful and important person in anther world and that the stories themselves describe only part of the world, which he then elaborates upon in a series of notebooks. (this has some similarity to the latest-aired
Doctor Who episodes, "Human Nature" and "The Family of Blood", by the way.)
Lindner discusses and confers with the client over minor details, at first in order to disprove them, then because he has gotten as obsessed as the client, until he half-believes in the other world. one day while Lindner goes on about some minor matter in the notebook, the client declares that he stopped believing and when he reveal that he no longer believes in the other world and pretended to do it because it pleased Lindner. Lindner then feels ashamed and admits to himself to the extent to which he has gotten pulled into the imaginary world. ever after, Lindner feels nostalgic over the notebooks and the world their represented.
though I have no hard evidence, I believe that Lindner embellished the truth a lot. the ironic way that events transpire just seem too perfectly and dramatically. actually I have trouble accepting he literally believed in his other life at all. maybe he just neglected work, had no interest in the real world any more and spent all his time scribbling his notebooks. I have even more trouble accepting that Lindner would get absorbed into the dream world to the extent that he describes.
the case seems to have insipred the Rog Phillips story "The Yellow Pill" and the Roger Zelazy novel
The Dream Master.