Diagnostic criteria for 14 psychiatric illnesses (and for secondary depression) along with the validating evidence for these diagnostic categories comes from workers outside our group as well as from those within; it consists of studies of both outpatients and inpatients, of family studies, and of follow-up studies. These criteria are the most efficient currently available; however, it is expected that the criteria be tested and not be considered a final, closed system. It is expected that the criteria will change as various illnesses are studied by different groups. Such criteria provide a framework for comparison of data gathered in different centers, and serve to promote communication between investigators.
John P. Feighner (1972) studied this question.