It's definitely not the same condition - like in most cases in psychiatry. Unlike in medicine, when you can often classify problems by their pinpointed sources

It's definitely not the same condition - like in most cases in psychiatry. Unlike in medicine, when you can often classify problems by their pinpointed sources (e.g. a virus/bacteria), in psychiatry it's usually a set of genes and other factors that comes into play, and various subsystems that broke down giving a certain outcome. We group psychiatric disorders the way we do it, because the science for distinguishing the sources of disorders isn't good enough yet to have a better system. It's similar to the taxonomy of plant&animal species before the advent of genetics. We had to group them by the way they looked, not by their real relationships.