LOL
People "self-medicate" with alcohol and, by "other substances," I'm going to assume you're talking about drugs? That's asinine. You don't self-medicate with that shit. You take it because you're pathetic and can't handle real life. Well, that or you enjoy the feeling of being drunk (to each their own). I've thought about killing people. I've thought about killing myself. I've thought about a bunch of things. That's all it is, though: thinking. If you have no self control whatsoever, then I'm definitely glad you've never flexed your mental capabilities. Those who're irresponsible with thinking and their actions (sorry, but you strike me as such) should not trust themselves with anything.
It's common for humans to question themselves and think about death. It comes with having awareness. I even think about what it'll be like when I die and how I'll die. Death is death, regardless if whether it's you dying or you killing. The way I see it, those who are religious should pray for someone to kill them. Heaven seems like a much better place than here the way people keep hyping it up. Don't you agree? If you're religious, I'll bet you can't wait to die.