Are you, or have you ever been, sick?

The New York Times ran an article, still available here, that almost begins like this:

"Researchers estimated that more than half of Americans would develop mental disorders in their lives, raising questions about where mental health ends and illness begins."

The article is quite interesting, but is the above a sensible question? Almost everyone will have a physical illness in their lives, but does that obscure our perception of good physical health?

The issue underlying the Times article, which I believe it never mentions, is: why is the diagnosis and treatment of non-physical illness so far behind the physical? We have nearly scientific methods of diagnosing many physical illnesses, and pretty clear ways of deciding when they are cured. We can test for bacteria, white blood cells and antibodies. Most illnesses are routinely handled by one type of treatment. (The Medpundit blog quotes Chekhov’s saying that "When many cures are offered for a disease, it means the disease is not curable." Most mental illnesses still have wide varieties of treatment.)
Diagnosis and treatment of mental illness might still be a hundred years behind the standard for physical illness. When is it going to catch up? How is it going to catch up?