Psychiatric Diagnosis and Classification - ResearchGate

26 PSYCHIATRIC DIAGNOSIS AND CLASSIFICATION
Limits of Our Knowledge about Mental Disorders
Classification of mental disorders creates great interest because it offers a
synthesis of our current knowledge of those disorders. A classification
reflects both the nature of mental disorders i.e. ontology) and our approach
to know them i.e. epistemology). Like the periodic table of elements which
displays properties of atoms in meaningful categories, the classification of
mental disorders mayyield some knowledge about the ``essence'' of underlying
mechanisms of mental disorders. At the same time, organization of the
classification mayreflect the conceptual path of how we know and group
various mental disorders. Having all this knowledge organized in a classification
presents a challenge for consistencyand coherence. It also helps us to
identifyshortcomings of our knowledge and leads to further research on
unresolved issues.
Classification of mental disorders has traditionallystarted from a practical
effort to collect statistical information and make comparisons among
patient groups. Todayits greatest use is for administrative and reimbursement
purposes. However, it has also gained importance as a ``guide'' in
teaching and clinical practice, because of its special nature of bringing
mental disorders into mainstream medicine. Since earlier practice of psychiatryand
behavioral medicine was mainlybased on clinical judgement
and speculative theories about aetiology, the introduction of operational
diagnostics allowed for demystification of non-scientific aspects of various
practices.
Current classification systems mainly remain ``descriptive''. They aim to
define the pathologyin terms of clinical signs or symptoms and formulate
them as operational diagnostic criteria. These criteria are a logicallycoherent
set of quantifiable descriptors that aim to identifythe presence of a
psychopathology. Our knowledge today, with a few exceptions, does not
allow us to elucidate the underlying mechanism as to what actually constitutes
the disorder or produces the symptom. The path from appearances to
essence depends on the progress of scientific knowledge.
As scientific knowledge advances, we become aware that the current
``descriptive'' system of classifications, however, does not fully map on
the neurobiologyin terms of its pathophysiological groupings. For example,
obsessive-compulsive disorder, which has been shown to have a totally
different neural circuit, has been grouped together with anxietydisorders
[5±7]. Similarly, despite the hair-splitting categorizations of anxiety and
depressive disorders with complex exclusion rules, clinical and epidemiological
studies indicate high rates of comorbidityand similar psychopharmacological
agents prove efficacious in their treatment [8±11]. Despite the
belief of distinct genetic mechanisms between schizophrenia and bipolar
disorders, familystudies have shown the concurrent heritability[12]. Such