I haven't done any studies on this or anything, but my instincts tell me that most people get depressed and stay depressed because of other people. I think most of us have people in our lives that treat us badly, which makes us feel worthless. We begin to think that if people we care about treat us like crap then people that we don't even know are going to treat us even worse...the seeds of low self esteem. Most of us know these people are bad for us and that we should get away from them, but it isn't that easy. They just keep returning. They do just the bare minimum to stay in the circle. I say "who needs um?" All they do is make us miserable.
I've been pissed off all day today because one of my "friends" made me wait for hours for them. He thinks his time is more important than mine. It ain't. People will say stuff like "oh you're too sensitive" as an excuse. Of course i'm sensitive, i'm depressed! If you treated me like a human being I wouldn't feel like a piece of shit all the time! They think you're desperate and maybe you are, but it doesn't mean you have to act like it. The more you allow people to disrespect you the more they think its okay.
I say get rid of the people that make you miserable and pay more attention to the ones that don't.
Hope you're doing well.