In most cases the consequences of depression are all too easily measured in lost productivity, less activity, kleenex consumed, duration in weeks of mood changes (say irritability) etc. Are you referring to "working depression" in which people fill time (usually working) because they are depressed but don't realize they are depressed and don't seek a diagnosis? Good diagnostitians are unlikely to miss this either, IF the patient seeks help (which they usually don't.)

Agreeing on a standard red line for treatment - when mood changes merit intervention, is a different topic, and a long one, weighing risks, the profound corruption of modern medical studies, etc.