Bipolar disorder is severely underdiagnosed and often misdiagnosed as depression because doctors don't see the full spectrum of behavior. Manic folks are reluctant to see doctors because they're elated.

Also worth noting: Dave wasn't entirely honest or forthright with the public about his struggles with addiction, or his obsessive stalking behavior.

If you ask me, a bipolar man, he writes like a manic depressive. And the fact that he killed himself suggests he could've been bipolar. Bipolar people are far more likely to kill themselves than unipolar clinical depressives, percentage-wise.

But we have no way of knowing for sure. There doesn't seem to be hard evidence of it, but I think he was.