Do psychiatrist treat people OR?

they damage your brains and what about chemical imbalances ( is it theory or actually happen in brain as they actually say neurotransmitters and ) does these medicines block receptors path ways or some thing like that as they say ( serotonin and dopamine ) D2 receptors , what happen if it is given to healthy person for around 4 yrs and then immediately st-oped are there any evidences that they treat persons mood or ill ness like schizophrenia or bipolar disorders . is psychiatry right profession i want to know that does any thing like mental illness exist Brain disease exist or they are doing big fraud with people .@ need professional advise @ and what are there results on body in brain after big crash of medicine and their side effect to normal human being