I have discussed this topic before, from the standpoint of someone who has experienced it from the inside looking out and from the outside looking in.  I've seen it from all sides.  I've mulled it over a lot, and dealt with it first hand.  I've been miraculously healed of depression and brought out of the deepest, darkest pit imaginable into freedom...and after that, to slip slowly back into it wondering why God left me...why was this happening...that time to be healed through doctors and medication.