Rep36 Understanding Personality Disorder

1.1.4 Validity of diagnosis and classification
The different categories of personality disorder
are human constructions (constructs); whether
or not they are theoretically valid or useful has
to be demonstrated through research. Systems
such as DSM-IV are intended to be theoretically
neutral classifications of mental disorders. In
the case of personality disorder, however, this
has resulted in categories that reflect a mixture
of personality theories. Many researchers
believe that this has led to a series of practical
problems:
I
The diagnosis of personality disorder has not
proved reliable or consistent when clinicians
base their assessments on unstructured
interviews (Mellsop, Varghese, Joshua &
Hicks, 1982).
I
Reliability has been improved through semi-
structured interviews (which give clinicians
clear guidelines for their questioning and
decision-making) and questionnaires, but
there are still difficulties regarding the
scientific and clinical validity of personality
disorder categories.
I
If different assessment methods are used,
agreement on the diagnosis of specific
categories of personality disorder is generally
low, which is ‘not a scientifically acceptable
state of affairs’ (Perry, 1992).
I
Although the DSM-IV classification identifies
discrete categories, many individuals
accessing mental health services meet criteria
for at least two, and often four or more
personality disorders (Stuart 
et al
., 1998).
This co-occurrence, or comorbidity, indicates
that the categories are not independent. 
I
Statistical analyses of the categories show that
there are three or four higher-order factors
or groups (Austin & Deary, 2000; Blackburn
& Coid, 1998), suggesting that there are too
many categories.
I
The specific DSM-IV diagnostic criteria do
not clearly discriminate between categories,
most criteria correlating with two or more
categories (Blais & Norman, 1997).
I
Most individuals with personality disorder
also have other forms of mental disorder, and
the distinction in DSM-IV between Axis I and
Axis II lacks a clear rationale (Livesley, 2001).
The distinction between the stable or
enduring traits of personality and the less
enduring symptoms of mental disorders
(Foulds, 1971) is useful, but not absolute. 
The DSM-IV classification is therefore seen by
many clinicians as having only limited usefulness,