Don't tempt me. I got 2000 words into my essay on this (it was too hard to resist ) when I realized I should point out that having to move away from your friends and feeling sad over that isn't depression, technically, and I recalled that you had moved recently, so possibly?
See, us humans are supposed to live in intimate harmony with each other to show the relationship between the trinity, and any separation feels like a loss, because it is a loss to be grieved. It's okay to cry this one out. Now if you were in depression before the move, then I might feel justified about posting a long essay on the subject on a kid's video game forum. insert self-conscious look here (Isn't that an adult subject, Miss_S?)
It is my belief that depression is caused by the sin nature, and genuine grief is not depression. Of course that distinction only makes the subject easier to talk about and is a distinction of language in my brain, though I find it to be a highly useful one to distinguish sadness caused by the sin nature and sadness caused by the truth of the reality we live.