I wouldn't use it as a long term solution, but I've had it help me before.

I have bipolar, and my first time trying opiates was during a particularly bad depressive episode. I had bought ~half a gram of Heroin, and my plan was to IV a bunch and OD. However, I had more than enough to do that, so I decided to sniff a bit before hand, so I could at least get an idea of what it would feel like.

However, while I was on Heroin, I no longer wanted to go through with it. I ended up spacing it out as much as I could, and by the time I ran out, my depressive episode had lifted to a much more manageable level.

That was nearly 3 years ago, and since then, I've used this method two more times.

So, my answer would be, only use it if your in a position where you actively have a plan for suicide, and fully intend to go through with it.

However, I can't speak to its effectiveness if you have something else like general depression or anxiety. It can work for bipolar, but that's because each episode only lasts for a temporary amount of time. I'd say that using it for anything even close to long term would not be viable.