Maud Newton, editor and writer, former practicing attorney, and college loan payer, blogs that depression is useful for writers. Rather than something that needs fixing, depression promotes highly analytical thinking:

Depressed people, they contend, tend to “dwell on a complex problem, breaking it down into smaller components, which are considered one at a time.”

As an added bonus, it's a two-way street; writing is good for depression (quoting from Scientific American):

...expressive writing promotes quicker resolution of depression, and they suggest that this is because depressed people gain insight into their problems.

I can see a new book from this: 7 Habits of Highly Depressed Writers