Clinical Depression.
Clinical depression (also called major depressive disorder, or unipolar depression when compared to bipolar disorder) is a state of intense sadness, melancholia or despair that...
Not in the way that you are asking. Depression is one illness; manic depression is a separate illness. However, it is possible that you are actually manic depressive or bipolar instead of just being...
There is no hard proof, though studies have been done to suggest there are specific genes that could indicate a higher chance of developing a depressive disorder later on.