Depression often results in me isolating myself from those around me. I tend to turn inward and sort of wallow in the comfort (Weird but that’s the closest thing that I use to describe the feeling) of being depressed. I usually do less role playing insofar as sitting down and playing the game but at the same time this is when I tend to get most of my creative work done. A great deal of world building happens during my episodes of depression even though there is not a great deal of role playing going on.
I’m prone to canceling my games when I’m depressed, assuming I have the time to even play or the people to play with, because I’m just not motivated to play; but Dungeons & Dragons and roleplaying games in general have always been my primary means of escaping into my own world (At least since the fourth grade or so) and I throw myself headlong into building and creating that world when I’m feeling down or anxious.
Being depressed does give you a lot of thinking time and because you want to be alone you can let your imagination and creativity do their thing without interruption so that can be a positive thing if you want to role up a character or create a campaign for players. In a live setting I cannot get into a game as much if I'm depressed while getting involved with role-play is very helpful if I'm bored.
Role-playing is a fantastic stress reliever and I suppose by extension helps to get you out of any depressed feelings. I do not play because I am depressed, I play because it makes me escape into a what could be situation just like watching a movie or reading a book.
Now that is an interesting question. I think I'm a bit of both. I apologize that its not a direct answer but sometimes I will commit to an Role-playing Game to forget my boredom and at the same time if I feel down I may not want to role-play at all.