According to Oliver James, a clinical psychologist and author of They Fuck You Up: How to Survive Family Life, the rise in numbers and popularity of emo acts may be linked to a rise in mental illness among their obvious target market of 18- to 24-year-olds (the age group most likely to be affected by psychological problems, according to studies published in Europe and Australia).
But if fans buy into it, that may be because rock music, unlike other art forms, is depicted as benefiting from being created by those with mental illness. Most critics would tell you Van Gogh's paintings are great despite, rather than because of, his psychiatric problems - but that's not true of the Beach Boys' Smile or Barrett's The Madcap Laughs or Nirvana's In Utero, for example, whose greatness is widely held to be inexorably entwined with their creators' mental problems.
It's the whole dionysiac genius thing; the myth, deeply ingrained in the Rockist mindset, that primal authenticity and true brilliance comes not from carefully honed technique, deep knowledge of the genre, cleverness or anything so square and totally un-rock-and-roll, but from abandoning oneself to the frenzy like a Viking berzerker. To give a topical example, crack-smoking, junk-shooting fuckup Pete Doherty is one of the greatest geniuses of our time, and his new band Babyshambles is ten times the band that The Libertines (who kicked him out) were, as the world would find out if he'd ever get his shit together for long enough to actually play a gig.
The article also mentions Ol' Dirty Bastard, as an example of the fine line between empathy and voyeurism. One notable omission, though, is Wesley Willis, described by Jello Biafra as one of the most punk-rock artists ever.
Of course, with the rising popularity of emo and various forms of fuckedupcore came a lot of opportunists putting on the "tortured genius" act, acting like caricatures of pissed-off, fucked-up, tantrum-throwing teenage nihilists and raking in the cash. Thirtysomething Universal Music executive and part-time teenage mook Fred Durst is one name that's mentioned there; and I'm sure you can think of other notable examples (anyone remember Vanilla Ice's reinvention as a tortured, angry-white-guy rap-metal mook? Or cyberpunk boy-band Information Society's post-Reznorian take-a-walk-through-my-nightmares industriogothic makeover?)
(On a tangent: Wikipedia's lists of songs about bipolar disorder and suicide)
Then add it. After all, it's Wikipedia.
What, L. Cohen's 'Suzanne' is not in the list? Don't the lyrics explicitly state "Suzanne takes me down to the river, where we slash our wrists..." ?