All types of depression are not the same and symptoms vary person to person. Similarly, there is no one cause of depression. Depression is influenced by a number of factors, including genetics, chronic illness, life experiences, and sustance abuse.
Perhaps some of you have figured out this riddle: If depression is heritable, what are its selective advantages? How could such a disadvantageous condition be passed on from generation to generation? As I see it, there are two possible answers to this question, and both have to do with a branch of evolutionary biology called evolutionary…