Heath Ledger death theories?

Um, yes I know this has been discussed millions of times over and I know it's not respectful really to discuss how one dies but I'm so curious about this...and I've seen some pretty horrid conspiracies about his death regarding Jack Nicholson. People always jump to the conclusion that Heath was doing heroin or crack or something. I see it everywhere, I mean, I thought this was just a simple anxiety-based situation where he ODed on sleeping pills after his joker role...