I saw the title of this OP and well, I had to read it.
Please do not take me as an example because as the above poster said, lots of females suffering depression are in long terms relationships; although i have no idea how healthy those relationships are.
With that being said, I have been single since I was 31 (I am about to turn 41). during the past decade, I have had two short term connections (2 months each, not even worth mentioning) and that is about it. I don't look either.
The main reason for my solitude is my MI. Luckily, I have come to learn to enjoy and appreciate my solitude. In summary, suffering alone has become the default and much more tolerable.
Again, please do not let my situation scare you away.