For those of you who will say that depression is caused by a chemical imbalance in the brain here is your answer.

i can sit and make myself get angry until i feel it surging through my system. i can feel the adrenaline flow. i can feel my heart beat faster. i can also sit and meditate until my heart rate lowers. i can stop tears by catching myself in the moment and then smile over how silly i am. i can feel so depressed to the point of physical pain in the chest that i want to put a plastic bag around my head with a rubber band around where it would cover my neck and in the next minute catch myself thinking about these things and laugh at myself from the outside looking in.

the point of all this is of course that you can heavily influence your body. i would be willing to put up large sums of money that i could cause a "chemical imbalance" in my brain by making myself depressed. and i will also bet that i can come out of it so that an "imbalance" no longer exists. just as you can psych up yourself before an athletic event and get your heart rate up and adrenaline pumping, you can also cause a chemical imbalance in your brain by thinking depressing thoughts. if you can stop those thoughts you will stop that imbalance.