Well, misery may spark creativity, but of a lower order than creativity sparked by joy, and the art reflects this.
The highest art lifts us above ourselves, above what we think of as the human condition, to a state that embraces the possibility of joy, if not leading immediately to a state of joy, itself.
Just below that is art that accurately portrays the human condition, misery included. I suppose in order to artciulate that misery one must know it intimately. I would bet tho that the act of creating, in that misery, lifts the creative one closer to their own joy.
So I suppose art created from misery may be therapeutic art-- to the artist, at least. To be therapeutic to the observer, it would have to be aimed at a place where the key aspect of the misery in that intersecting moment is the familiar internal message, "I am alone in this." That spot in us can use a little misery-portrayal, in the early stages of any particular healing, but it's not satisfing for long, unless one considers addiction to be satisfying; it can be quite addictive. I guess for the artist as well.
Hey! If we are created in God's image, do you s'pose he was having the misery when He created that, um, whatchacallit, "Creation"? :~)
~Susan
On the other hand-- No denying brain chemistry has an effect on creativity, but the manic state at least appears to be equally as productive as the depressed....