Re: what does one do..
yes a very dear freind of mine have had a deep depression, it was very difficult to help, because she got very very passive, and sometimes she wouldnt admit that she needed help and something was wrong with rest of us but not her. It takes time and it is very toughf and requires a lot of patience . my suggestions is first of all professional help.
what you can do is to be there for that person, lend a shoulder when he/ she wants to cry, listen when that is required, but with balance , dont let the person sink in to all self pitty.
get that person out of the house for a walk, see a movie or what ever the person used to like to do. It is not certain that he or she wants to do that, but insist on doing that.