The treatability of depression, as defined by the likelihood that you eventually get these people to claim they're better, doesn't tell me how much they suffered before getting to this point, whether they would voluntarily go through it again to survive, and what their future risks of recidivism are.
However much they suffered before that point, and whether they would go through it again to survive, are not relevant points to whether they should be glad that they didn't die. They're sunk costs. A person might be tortured, and have a long life of good quality afterwards (data point, John McCain,) and it's possible that they would not be willing to go through torture again to survive, but this doesn't mean that they won't be glad that after they were tortured, they didn't die, even though they might have killed themselves to escape the torture if they could.
There's certainly a possibility of biased reporting among people who report their quality of life and whether they're glad they're alive among people who've formerly attempted suicide, but then, that possibility exists among everyone, since whether you've attempted suicide before or not you're still subject to social stigma if you admit to wanting to die.
As it happens, I know quite a lot of people who've attempted suicide. Of those, all of them currently appear to have qualities of life that are fair to good. In fact, one of the apparently happiest people I know attempted suicide about a decade ago. It's possible that these people are systematically misrepresenting themselves to avoid social stigma, but at this point you'd be starting to get into invisible dragon depression territory.
However much they suffered before that point, and whether they would go through it again to survive, are not relevant points to whether they should be glad that they didn't die. They're sunk costs.
Subtle distinction: A person's being glad that they are currently alive is not the same thing as their being better off, in total, by not having died at an earlier point X. This is relevant because the central argument for non-consensual suicide intervention is pointing out the former as evidence for the latter - incorrectly, I think. From the perspective of imminent suicide and its possible prevention, the intermittent suffering before eventual (potential) recovery is not a sunk cost yet!
Last month, two people far at the periphery of my social circles have threatened suicide. Seems like a sign for me to learn some ledge-fu.
I reviewed the stuff I'd learned back in high school ("Listen." "Be supportive." "Don't argue." "Etc etc etc.") I have trouble believing that this would work outside of movieland, especially on strangers. More so, in person I'm an awkward, fidgeting introvert---the impact of everything I say is thus diminished, and I sound very insincere or clinical, like I'm following a bad movie script, when I say anything like, "You are not alone in this. I’m here for you." or "How can I best support you right now?" I doubt that this would sound any better in writing.
I suppose I could split my question into two related ones: what would you say to a person threatening to commit suicide, 1. in person, and 2. in an email?
I'm looking for out-of-the-box ideas that don't rely on charisma or compassion shining through. Personally, if I ever need to talk myself out of suicidal thoughts, I apply the "bum comparison principle": if my life is so crummy that I'm willing to commit suicide, then I should be willing to just walk out on everything I value and drift off in a random direction, survive by dine-and-dashing out of cheap restaurants and wash dishes if I get caught, maybe take odd jobs or hitchhike or gather roots and berries or blog from public libraries. I don't see this possibility in a negative light, and yet I still haven't done it. To me, it means that however bad my life may seem, I'm still too attached to it to walk out; therefore, suicide isn't on the menu.
People have different reasons to want suicide, and I understand that what works for me with my first world problems probably won't work for a person who is in too much physical pain from an incurable disease. To the best of my knowledge, the two people I mentioned earlier are both unskilled laborers who had lost their jobs, one of them so long ago that he's no longer eligible for unemployment benefits. I don't think I'll meet these particular people again, but I'd appreciate everyone's thoughts on what I could've said if my brain hadn't frozen.