I think they are more alike than dislike in many instances. I "do" throwing up too and it is partly by that that I am diagnosed as having the flu. When I stop throwing up, I don't have it anymore. I "do" not being interested in life/getting out of bed/bathing and it is partly by that that I am diagnosed as having depression. When I get up and get going under my own will/steam, I don't have it anymore.

There are always physical attributes to mental illnesses and mental attributes to physical ones; people with heart problems often have depression and vice versa, for example: NIMH - Depression and Heart Disease

The body is "whole", we just divide up "types" of illnesses as a help in knowing how best to approach and treat them.