Just a Thought. Please Excuse the Emo Tone.
I think when a person goes through something that is so traumatic, so painful and tragic, they develop one of two problems: They either become completely unable to feel anything anymore or the exact opposite occurs, they feel too much all the time.
That balance disappears.
And I think a lot of what depression is all about is just that; the struggle to return to that balance.
Just a thought I had while listening to this super emo song by Mazzy Star.
-jess