In response to the poster's original question (In relation to the schizophrenia aspect, anyway)
It isn't possible to induce schizophrenia by opening your mind too far- schizophrenia can be brougt on, but it's usually by a specifically large or unsettling event (such as the witness of a death or loss of someone close to you.) Even this is not the most common cause of schizophrenia, not by far. It's a genetic disease, so I wouldn't worry too much about it, anyway.
I would imagine that you can convince yourself that something is true when in reality it is not- I just don't think it would go so far as to be regarded as a mental illness.
As for the other aspects of your post (or other forms of mental illness), I don't know.
You make a very interesting point.