Smoking will eventually make everything worst for you. You will start battling with addiction on it too and that makes it two different problems for you. I would suggest trying as much as possible to resist the urge to smoke.
A lot of things can actually make someone to start feeling depressed and it depends on the magnitude of the effect that thing have on the person that it's been affected. As for me, I started feeling depressed when I was abused sexually by our house maid 10 years ago.
It's always very sad seeing your own kid suffering. But it's a good thing that she's been taken care of right now and that's all that matters. In no distant time, she's going to fully recover.
Most people don't even understand what depression is all about. No matter how much you try to explain to them what depression is affecting you, they will not understand. As a result of that, I don't bother telling them I'm depressed.