As managed care is tightening its ever present grip, full psychiatric diagnostic interviews are being marginalized. This is especially true in the so call “collaborative care” models, in which psychiatrists merely advise primary care physicians without necessarily seeing the patient themselves.
Very Frequently = 5
Having never seen this, the average person does not know how bad depressive symptoms can be – unlike an experienced psychiatrist who has seen the whole gamut of depressed feelings. They therefore will not compare themselves to that, which is actually the relevant comparison!
So each test taker is, in effect, creating his or her own scale. What seems like "often" to them might not seem like very often at all to someone else. This makes the results next to meaningless for making a real diagnosis.
I think the reader will see how it is quite possible that both of these very different individuals might answer the PHQ-9 questions in almost the exact same way, and come out with identical scores. The first would benefit from an antidepressant. The other would not, and probably needs marriage counseling instead.