I've also always really liked the dark and introspective music, yet never really thought of it in terms of "depressing." I guess I've always considered it "real" and all those other, like terms. Perhaps it's the difference of being on the inside looking out, or the outside looking in. That's not to say that I dwell in depression, as I don't. However, the songs that deal with those deep inner spaces, the dark and the light, have always resonated with me.
That's funny what you say about the happy music causing them to feel agitated. Not all [by any means, as there are a number of up/positive/etc. songs that I love] "happy" songs cause me to feel that way, however, I have experienced that when I've felt down, and know the resentment and the feeling that my feelings were being discounted that, that created. The "hey, cheer up


Thanks for giving us the mental health perspective.
Love, Lizzytysh
Kush: This answer was also meant to include you, as I read your post first.