When Do Two Presentations Count as the Same Disorder? Identity Criteria in Psychiatric Classification
Four research programs contend over psychiatric classification: the DSM, the Research Domain Criteria, the Hierarchical Taxonomy of Psychopathology, and network theory. Each presupposes an answer to when two clinical presentations count as the same disorder, and the answers differ in kind: membership in a stated symptom rule, dysfunction in a functional system, position in a covariation-derived space, occupancy of a self-sustaining network state. With the case-control design and the Psychodynamic Diagnostic Manual’s prototype resemblance there are six criterion kinds, and sameness under one does not transport to another. At the grain the programs’ definitions license, the only class on which all six agree is the individual patient.