Psychiatric Diagnosis and Classification - ResearchGate

12 PSYCHIATRIC DIAGNOSIS AND CLASSIFICATION
distinguishable by this means from other syndromes [29]. Other more elaborate
statistical techniques have been developed more recently. For
example, a means of identifying clinical groupings by a combination of discriminant
function analysis and admixture analysis was described by Sigvardsson
et al. [30] and used to demonstrate two distinct patterns of
somatization in Swedish men. Woodbury et al. [31] developed a ``grade of
membership'' GoM) model for identifying ``pure types'' of disorders and
assigning individuals to these in a way which explicitly recognizes that
natural classes have fuzzy boundaries and therefore allows individuals to
have partial membership in more than one class [32]. Faraone and Tsuang
[33] also proposed using ``diagnostic accuracy statistics'' a variant of latent
class analysis) to model associations among observed variables and unobservable,
latent classes or continuous traits that mediate the association.
The central problem, therefore, is not that it has been demonstrated that
there are no natural boundaries between our existing diagnostic categories,
or even that there are no suitable statistical techniques, data sets or clinical
research strategies for determining whether or not there are any natural
boundaries within the main territories of mental disorder. The problem is
that the requisite research has, for the most part, not yet been done. The resulting
uncertainty makes it all the more important to clarify what is implied
when a diagnostic category is described as being valid [34].
Clinical Relevance
The clinical relevance of a classification encompasses characteristics such as
its representative scope coverage), its capacity to describe attributes of
individuals such as clinical severity of the disorder, impairments and disabilities)
and its ease of application in the various settings in which people
with mental health problems present for assessment or treatment.
It is obvious that a classification should adequately cover the universe of
mental and behavioral disorders that are of clinical concern. The list of
diagnostic entities is open endedÐnew diagnoses may be added and obsolete
ones deleted. There is no theoretical limit on the number of conditions
and attributes to be included, but the requirement that new rubrics should
only be added if they have adequate conceptual and empirical support, as
well as practical considerations e.g. ease of manipulation), calls for strict
parsimony in any future revisions of the scope of the classification.
The system should be capable of discriminating not only between syndromes
but also between degrees of their expression in individual patients
and the severity of the associated impairments and disabilities. This implies
that the multiaxial model of psychiatric diagnosis is likely to survive,
subject to further refinement. By and large, a multiaxial arrangement