split-personality disorder 
noun
Less common term for multiple-personality disorder.As almost everyone knows, Gollum is the character from The Lord of the Rings trilogy with a severe split-personality disorder....
- I think I'm going to have to fall back on my original diagnosis of Kristof as a columnist with split-personality disorder.
- This gripping first novel is a moving study of split-personality disorder and of a psychiatrist's desperate efforts to rescue a tragically lost soul.