The main issue I have is that people think our understanding of mental illness / psychiatry is as good as say pathology.
My main point is that, from my own person experiences through the whole system, treatment seems the most broken aspect. Diagnosis of depression is possible without a blood-test, as are other physical illnesses, the signs are obvious. The treatment is not as trivial, you won't do well to "let it run it's course", the drugs are gruelling and may not even work and therapy requires drive a depressed person hasn't got.