Psychiatric Diagnosis and Classification - ResearchGate
Psychiatric Diagnosis and Classification - ResearchGate
Psychiatric Diagnosis and Classification - ResearchGate
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INTERNATIONAL CLASSIFICATIONS 37<br />
on the dimension. Clinicians are obliged to use categorical concepts, as they<br />
must decide who is sufficientlyill to justifytreatment. But, in our efforts to<br />
underst<strong>and</strong> the relationships between social <strong>and</strong> biological variables, dimensional<br />
models are far more appropriate [33]. Dimensional models are<br />
more consistent with the polygenic or oligogenic) models of inheritance<br />
favored for most mental disorders. These models assume that a number of<br />
genes combine with one another <strong>and</strong> interact with the environmental factors<br />
to cause the disorder. Persons can thus have various doses of the risk factors<br />
that predispose to the illness <strong>and</strong>, depending on the dose, the severityof the<br />
manifest condition mayvaryalong a continuum. Such approaches have<br />
been shown to provide important clinical advantages with psychotic illnesses<br />
[34] <strong>and</strong> personalitydisorders.<br />
Though psychiatric disorders are construed to be disorders of brain chemistry,<br />
a fundamental notion underpinning the classification systems is that<br />
different disorders represent different classes of disturbance of mental life.<br />
These categories thus must be understood as being distinct not onlyamong<br />
themselves but also from ``normality''. In psychiatric classification, therefore,<br />
categories can be seen as mathematical sets which, based on their properties,<br />
can be reliably<strong>and</strong> meaningfullyplaced in valid classes of similar objects.<br />
These categories are often nominated bymeans of descriptive parameters<br />
which then lead to categories that are big or small depending on our purpose,<br />
as noted earlier. <strong>Psychiatric</strong> classifications attempt to define classes<br />
not just bypositive defining parameters but also byexcluding other possibilities.<br />
In other words, categories are defined according to the principle that<br />
members of each categoryare more similar to each other than to members of<br />
other categories. The attempt is thus to make the categories more internally<br />
consistent. In addition, to separate or distance the categoryfrom others we<br />
employexclusion criteria in order to prevent overlap between categories.<br />
However, it is not sufficient just to have categories that are internally<br />
consistent. Theymust also be meaningful, <strong>and</strong> membership of a category<br />
must also be able to predict more about the member than what is said in the<br />
inclusion rules alone. Further, once an exhaustive list of categories has been<br />
achieved, theymust be sorted according to some larger principle in order to<br />
make such a list more manageable <strong>and</strong> identifya purpose. This also ensures<br />
the comparison of like with like, i.e. the comparison of categories that are<br />
understood to be at the same level of complexity. This, however, means that<br />
at the same level of hierarchywe cannot have categories that are determined<br />
according to totallyunrelated parameters. In anycategorical system it is<br />
imperative to ensure that the elements sort into discrete groups; otherwise,<br />
the implication is that either the sorting rules were incorrect or the categories<br />
did not exist.<br />
Especiallywith regard to the categories of personalitydisorders, this<br />
problem becomes exemplified when researchers assess everycriterion in