As an MD Psychiatrist and Psychoanalyst, I agree entirely with the sentiments of Gary Greenberg.
I do not have time to go into it now, but I tend to think that the whole thing is a pseudo-medical charade, designed for the drug industry and for the insurance industry's convenience.
If "mental health" cannot be defined, how can you draw lines to define "mental illness"? You can, at the extremes, but otherwise you can't. Everybody is a little nuts.