Media about mental illness and drug abuse: I wholeheartedly recommend Methland. Trainspotting isn't so much about drug abuse or mental illness as it's about Scottish thugs. My suggestion is you read the glossary first. I didn't know it was there until I'd finished the book.

Tim Hunter directed a movie called The Saint of Washington Park which is about mental illness and homelessness. It's okay. A Beautiful Mind isn't about mental illness or John Nash; it's about Akiva Goldsman and Ron Howard's magical imaginary friends fantasy about what they think moviegoing audiences believe mental illness is about. Ingmar Bergman's Through a Glass Darkly, on the other hand, does a pretty good job of exploring schizophrenia in 1961.

The gold standard druggie movie is probably Drugstore Cowboy, William S. Burroughs and all:

My sister keeps harping on The Glass Castle because she says I'll relate to it. The primary difference between me and my sister is my sister thinks my mother is a lovable scamp who happens to be batshit insane. I have a bit more of a "Mommie Dearest" perspective.