I think he is saying there is a need to discern "the true nature of the human problems called mental disorders" (emphasis added) in order to distinguish actual mental illness from other human problems. In my own case, for example, so-called "mental illness" is not at the root of my depression even though "mental health" is required in order for my life to not be completely dominated or over-run by my depression. So, and just as with so-called "heart disease" (where there really is no such thing), the challenge is to look beyond the broad brush -- so-called "mental illness" -- and get down to actual causes and conditions.