There was a time when “depression” was used to describe everything from sadness over a failed a test to a chemical imbalance causing sufferers to desire death because they are incapable of coping. And in fact, among lay people there is still no distinction between situational depression and clinical depression. People still tell clinically depressed people to “get over it” and are surprised when they suicide.
Which is why I believe it is not a bad thing to refine our understanding of these illnesses.
Medical research has discovered much, and not just within mental illnesses. “Asthma” is a diagnosis made only when the sufferer’s symptoms get better with the use of asthma medication. And I don’t see any problem with this.
But In spite of those doctors who believe themselves godlike, the field of medicine is built on guesswork based on trial and error.