Depression is often repressed anger, and it needs to be worked through and directed, but self-destruction is just the ultimate repression.
I don't mean to pick on you, FF, because as NJQT stated, you are often one of the most interesting, fun, and intelligent posters.
However, this line of thinking is one that is being revised at least slightly in currrent psychological theory. I don't think that it's altogether wrong at all-- I just think that it's becoming evident that a lot of depression, anxiety, and other mental illness have a clear biological component. Whether this biological predisposition causes people to process anger to depression or whether this is simply a coping mechanism people use to deal with funky brain chemistry is still up for debate.
I'll admit, I'm very angry, but I don't know which came first-- the anger and dark emotions that make me depressed or the depression that makes me angry and sad over the lost opportunities and years of my life. I'm more of the mind that the anger I feel is a result of depression, anxiety, and mental illness than the depression being suppressed anger. It can become a vicious circle as well as a nasty positive feedback loop that therapy and medication together hope to short circuit.
Unfortunately, even the best mental health professionals have a hard time separating what is truly biological from what is psychological.
