Our expert says:
Look for any basic psychology textbook, which should discuss personality disorders in detail, and even a google search should turn up mounds of material.
There is no such thing as a Split Personality, that was an ignorant and mistaken journalist's popular term, at one time, for Schizophrenia. What you describe in your friend is indeed odd, and must be very frustrating for you, but there's not much that can be done about it unless and until he recognizes that there is indeed a problem, and he sees a shrink for an assessment and advice.
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