I'm ashamed I didn't think about this one earlier: "Asylum" by Supertramp ("Crime of the Century" album). "But don't arrange to have me sent to no asylum. I'm just as sane as anyone."

Virtually anything written by Roger Waters (ne Pink Floyd) that isn't about war is about insanity. See particularly "Total Eclipse" ("Dark Side of the Moon" album) -- "The lunatic is on the grass...."

"Toys in the Attic" (Aerosmith, album of the same name) of course.

And much, much more....

Alex