I read an interview with him, can't remember when it was, I think it was around Superunknown or thereabouts, where he said there weren't many times since his youth that he wasn't depressed to a certain degree. If I remember correctly, he said that's where a lot of the music came from, the feeling of it.
RE Day I Tried To Live, I think that was in response to Kurt Cobain's death, or possibly Andrew Wood's addiction / death. I think during the same interview, Cornell alluded to something of that nature...
The tone of the music and lyrics of Soundgarden's music always struck me as something other than suicidal in nature, I thought Cornell would live forever.... Just had a fighter quality about his persona, but obviously, there was a lot going on inside him that was hard to figure, and now such songs as Pretty Noose have a different feel to them.
I used to sing that song in karaoke, and do a decent job of it. I don't think I'll be able to sing it for a while, because of the words....
RE: the toxicology. I wonder how much of the barbiturates was due to needing sleep? I.e. a sleep medication, as opposed to misuse? From reading the article, it looks like it may have been a mishap, and the side effects led him to do something maybe he wouldn't otherwise have done. I guess we'll never truly know.