Table 5-4 presents a summary of the eight major
issues discussed below.
Categories Versus Dimensions. Essentially, the
mental disorder categories represent a typology. Based
upon certain presenting symptoms or upon a particular
history of symptoms, the patient is placed in acategory.
This approach has several potential limitations. First,
in too many instances, it is easy to confuse such
categorization with explanation. If one is not careful,
there is a tendency to think “This patient is
experiencing obsessions because she has obsessive-
compulsive disorder”or“This person is acting psy-
chotic because he has schizophrenia.”When this kind
of thinking occurs, explanation has been supplanted by
a circular form of description.
In addition, as noted earlier in this chapter, abnor-
mal behavior is not qualitatively different from so-
called normal behavior. Rather, these are endpoints
of a continuousdimension. The difference between
so-called normal behavior and psychotic behavior,
for example, is one of degree rather than kind
(Chapman & Chapman, 1985). Yet mental disorder
diagnoses in terms of categories imply that individuals
either have the disorder in question or they do not.
This all-or-nothing type of thinking may be at odds
with what we know about how symptoms of psycho-
pathology are distributed in the population. For exam-
ple, a categorical model of borderline personality
disorder (BPD), as presented in theDSM-IV-TR
(i.e., present vs. absent), may not be appropriate
because individuals differ only with respect to how
many BPD symptoms they exhibit (a quantitative dif-
ference). In other words, the categorical model may
misrepresent the true nature of the borderline construct
(Trull, Widiger, & Guthrie, 1990). In fact, there may
be relatively few diagnostic constructs that are truly
categorical in nature (Widiger & Trull, 2007).
To illustrate, consider Figure 5-3, which presents
dimensions of worry, anxiety, and fear that are char-
acteristic, in extreme form, of an anxiety disorder.
This example concerns a person’s experience when
anticipating and potentially going on a job interview.
When considering dimensions relevant to psycholog-
ical disorders, it is helpful to organize these according
to thoughts, emotion, and behaviors. One can see that
thoughts anticipating the interview range from those
associated with some degree of confidence to those
more characteristic of fear and dread. Likewise, emo-
tional experience may range from physical arousal that
is helpful to that which is maladaptive and disruptive.
Finally, behavioral responses to this situation range
from attending the interview to various degrees of
avoidance. As noted in Figure 5-3, it is only when
our thinking patterns, emotions, and behaviors cause
great distress or problems that we consider these indic-
ative of a disorder, in the diagnostic sense. However,T A B L E 5-4 General Issues in Classification
Categories Versus Dimensions
Is the categorical model adopted inDSM-IV(i.e., the dis-
order is either present or absent) really appropriate? Is a
dimensional model preferable?
Bases of Categorization
Should there be multiple ways of making diagnostic
judgments? Does this create too much heterogeneity
within a diagnostic category?
Pragmatics of Classification
How do we decide whether a condition is included in the
diagnostic manual?
Description
Are the features of the diagnostic categories adequately
described? Are the diagnostic criteria specific and
objective?
Reliability
Are diagnostic judgments reliable? Can different diag-
nosticians agree on the classification of an individual?
Validity
Can we make meaningful predictions based on our
knowledge of an individual’s diagnosis?
Bias
Are the features of the disorders inDSM-IVbiased
against particular individuals because of their gender,
race, or socioeconomic background? Are diagnosticians
biased in their interpretation or application of the diag-
nostic criteria?
Coverage
Do theDSM-IVdiagnoses apply to the people who pres-
ent for psychological or psychiatric treatment? Is the
DSM-IVtoo narrow in its coverage, or is it too broad?
DIAGNOSIS AND CLASSIFICATION OF PSYCHOLOGICAL PROBLEMS 147