Psychiatric Diagnosis and Classification - ResearchGate

30 PSYCHIATRIC DIAGNOSIS AND CLASSIFICATION
because of recognizable patterns of co-occurring symptoms rather than because
of a true understanding of their distinctive nature that would make
them discrete categories within a classification.
What Defines a Mental Disorder
While ICD is a classification of diseases or ``disorders'' in the context of
mental illness), there is no explicit agreement on the definition of a mental
disorder. Despite the call for a definition [21], no agreement has been
forthcoming and this ambiguitycreates a fuzzyboundarybetween disorder
and wellness. At the lowest level, a mental disorder is an identifiable and
distinct set of signs and symptoms that commonly produce disability, and
that the healers in the societyclaim to be able to ameliorate through various
interventions. While practical, such a definition can lead to error, e.g. homosexualitywas
once defined as a disorder.
The answer to the question ``What is a disorder'' needs to be evaluated
against rigorous scientific standards rather than just from societal or personal
points of view. A disorder maybe defined bya set of general principles
that characterize a specific entity, such as common aetiology, signs
and symptoms, course, prognosis and outcome. It may then have other
correlates, such as familial aggregation due to genetic or contextual factors),
a pattern of distress or disability, and a predictable range of outcomes
following a varietyof specific interventions. Robins and Guze [22], in their
classic paper, proposed five phases for establishing the validityof psychiatric
diagnosis: clinical description, laboratorystudies, delimitation from
other disorders, follow-up studyto show diagnostic homogeneityover time,
and familystudyto demonstrate the familial aggregation of the syndrome.
Experience gathered since then shows that some of these criteria lead to
contradictoryconclusions. For example, if one wants to define schizophrenia
byits diagnostic stabilityover time, the best approach is to define the
illness at the veryoutset bya duration criterion of six months of continuous
illness, which tends to select for subjects with a poor outcome. In contrast,
the familial aggregation of schizophrenia is best demonstrated when the
notion of the disorder is broadened to include the notion of ``schizotaxia''Ð
a broad spectrum notion that views the predisposition to schizophrenia to
be characterized by negative symptoms, neuropsychological impairment
and neurobiological abnormalities and schizophrenia to be a psychotic
neurotoxic end-point in the process. The latter approach suggests that
narrowing the definition of schizophrenia using the former strategymay
in fact hinder progress in identifying the genetic causes of the disorder [19].
The lack of a definition of what is a disorder also creates an ambiguity
about so-called ``sub-threshold'' disorders. Manyhave shown the presence