I think depression is a common thing, alot of people feel 'blue' or whatever sometimes. I think alot of depression is also situational, like, you lost a job/friend/wallet/or whatever. I think med school is also a setup for depression in some ways because well, this medical student would study by herself and long hours by myself, studying stuff that I am not sure I can cover in the short time alotted - it was just freaking me out.
The diabolical thing about depression is that when you are depressed, you tend to think: nah! this is the
REAL way to look at the world and I will always feel like this. I am sort of used to this now and so I am like, ok wait - that's just your depression talking ... Sometimes, I feel like I have to treat my depression like an awkward country cousin who's come to visit - sometimes unattractive and rough, but just visiting. "Oh, heck, it's you again!" But they're family and so you have to deal with them.
Go and talk to a friendly counselor and debrief your feelings. Talk therapy is priceless, and we all need the help sometimes.
oh, and another thing!! I also believe that depression is 'anger turned inward,' so I ask myself: what are you really angry about? when I feel super depressed. Sometimes, I need to get angry and deal with a situation or person that I have been just stuffing my feelings about. Hence, the value of talking to a good counselor ...