Okay, a little revelation here. Being a combat veteran, I experience great depression at times. Meditation is a part of my daily ritual and it helps tremendously.
The key to this is what you focus on, where you allow your mind to go, and frame of mind you have when you begin.
Practice when you are feeling the least depressed, focus on a pleasent memory or a hopeful future, and only allow your mind to expand within the limits of that thought.
Yes, depression is a chemical-biological issue (endocrinology, if you care to study it), but can very effectively be handled with meditation.
Best wishes on your journey!