The chemical imbalance in the brain gets affected from different moods or emotions we have. The good or the bad feeling, the feeling of happiness, the feeling of love, and hate, all resides in brain and it releases particular hormones to give that feeling and emotions. So again, the guy above rightly pointed out that it also depends on you, how you control that chemical imbalance.
That's why all doctors agree the surprising power of positive thinking in healing any disease. Your problem is all mental, nothing physical. But even physical diseases get healed by the power of positive thinking. Placebos are recommended by doctors even when they have no effect as research has proved that people who take placebos get healed quickly than others as they think the drug they are taking will heal them.
Finally, psychatrists here in Pakistan (and generally all docs here) are quick to diagnose something (due to their limited knowledge) based on a very curosry analysis of symptoms they perceive. Remember, symptoms may lead to a number of disease, or they may actually be just perfectly normal for someone to have.
To say you have bipolar disease is something serious, do not led him to believe that you have got it, or else it may happen that you may end up having it because you will get paranoid. First confirm it from 2-3 other good psychatrists. I'm sure, going by the quality of medical professionals here, everyone will have a different story to say.
