'Angel Baby' (Australian) a love affair between two mentally-ill people, a moving and sad film which swept the Australian Film Institute Awards (best picture, director, and actors)
'Angels of the Universe' (Icelandic) a man developes schizophrenia after a bad love affair, very eloquent and somber
'Betty Blue' (France) a classic
'One Flew Over the Cuckoo's Nest' (American) classic Academy Award Winner
'A Beautiful Mind' (American) winner of some Academy Awards
'Girl, Interrupted' (American) Academy Award Winner
'The Caveman's Valentine' (American)
'The Saint of Ft. Washington (American)
I mention the American movies since they are also good films about mental illness.
Hope this helps.