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Diagnosis in psychiatry is currently based on phenomenology, because etiology and pathogenesis are largely unknown, and because biological markers for disease have not been identified. The unitary model of depression and the model of a bipolar spectrum are based on resemblances in phenomenology between symptoms whose pathogenetic pathways are likely to differ. Both models have sometimes considered the diagnosis of personality disorder as an affective variant, even when patients present with qualitatively distinct mood features. Biological reductionism lies behind a concept of mood as the primary driver of psychopathology, a view that may be detrimental to treatment.
PHENOMENOLOGICAL CLASSIFICATION AND THE DSM SYSTEM
What is the basis of a classification of mental disorders? Ideally, diagnosis should be rooted in an understanding of etiology and pathogenesis. But we still know too little about psychopathology to reach that goal.
The current system, DSM-IV-TR (American Psychiatric Association, 2000) continues an approach that originated in DSM-III. In earlier editions of the manual, some categories (notably the group of neuroses) had been defined on the basis of etiological theories. The problem was that these models were wrong. Concepts such as "unconscious conflict," based on psychoanalytic models, were (and remain) unverifiable using empirical methods. To avoid this mistake, DSM-IIIl, and its successors, defined almost all disorders phenomenologically and atheoretically.
DSM categories were considered to be provisional solutions, until such time as etiology and pathogenesis become better known. Yet with the passage of time (and with painfully slow progress in etiological research), these diagnoses took on a reality of their own.
Currently, most categories in psychiatry are syndromes, not diseases. (The term disorder was introduced as a way of acknowledging that problem.) Thus, DSM diagnoses do not have the same status in medicine as pneumonia or cirrhosis of the liver. Some syndromes are phenotypic variants that could eventually be folded into a broader category. Others are broad and heterogeneous diagnoses that could eventually be divided up into smaller categories.
As the history of medicine shows, phenomenological resemblances are no substitute for an understanding of cause and effect. Anemia and jaundice look alike, but can be caused by a multitude of disease processes. Psychiatry will eventually undergo a similar evolution (Paris, 2008a; Shorter, 1997).
In an attempt to make diagnostic practices more...