No doubt it's a spectrum. Like autism, near-sightedness, and skin color. I'm a doc in the military, where there has been a striking uptick in depression and related issues. At some point, in the clinic, you've got to make decisions, and the analytic rheumination hypothesis is useful. Are there other kinds of depression? Probably. Is it possible to get caught in a downward spiral from which one can not escape on their own? Sure. Could the AR hypothesis still be relevant in some of those cases? Absolutely.