There is currently alot of research being down on brain trauma. In one area in particular is repetative injury due to sports. It is quite facinating and frankly scary. we now know that repetative blows to the brain can cause lasting life-long sequalea in all kinds of areas
Google brain Trauma for starters. Then brain trauma/depression. Brain trauma/mental illness. Neurology would probably be your best discipline for answers that you seek although the other disciplines are intertwined. Sounds like you have some facinating learning ahead of you. Hope it helps!