Do you know what causes the "chemical imbalance?"
The chemcial imbalance school subscribes to the same logic that an airplane wreck was "caused" by the plane's contact with the ground.
That's why prayer and other methods do more to "cure" a person of depression, anger, anxiety or other unhappy conditions. I'm not condemning anyone here who chooses to use such drugs, just presenting a point of view that makes total sense to me and works. And doesn't cost any money, has no bad side effects (just good ones!) and has a long history behind it!
Plus, there's every possibility that if the brains of depressed people have certain characteristics, maybe the chemical imbalance is the result of the depression, not the cause!! Just like increased adrenalin is the result of fear, not the cause.