IndieSoul-
I definitely loose interest in doing things when I get depressed, even if I'm not particularly sad. I loose interest even in basic things like reading and watching TV, working on research, and hanging out with friends. It tends to be a constant for me when I get depressed. Part of my lack of interest seems to for me to be connected to my inability to concentrate on the things I would otherwise enjoy. If I can't concentrate for more than a couple of minutes on something, even something basic like reading becomes a task and hence not enjoyable. I hope you are feeling better soon.