398 TREATMENT OF SPECIFIC ANXIETY DISORDERS
come (see Holaway, Rodebaugh, & Heimberg, 2006; Rodriguez et al., 2005; Yonkers
et al., 2000). In the NCS-R, 85% of individuals with DSM-IV GAD had a comorbid
condition (Kessler, Chui, et al., 2005; see also Carter, Wittchen, et al., 2001; Mofitt et
al., 2007). Similar high rates of comorbidity have been found in clinical studies with
the most common being major depression, social phobia, and panic disorder (e.g.,
Brown, Campbell, et al., 2001). Moreover, individuals with GAD or panic disorder
with agoraphobic avoidance are more likely to have a substance use disorder than indi-
viduals with other mood and anxiety diagnoses (Grant et al., 2004). Finally, between
one-third and two- thirds of individuals with GAD will have an Axis II personal-
ity disorder, the most frequent being avoidant, obsessive– compulsive, and possibly
paranoid and dependent personality disorders (e.g., Dyck et al., 2001; Massion et al.,
2002; Grant et al., 2005; Sanderson et al., 1994). GAD is most often the temporal
primary disorder, especially in relation to the mood disorders (Kessler, Walters, &
Wittchen, 2004).
Clinician Guideline 10.7
Most individuals with GAD will have a current or lifetime history of other psychiatric disor-
ders that will complicate response to treatment. The most common secondary diagnoses are
major depression, social phobia, panic disorder, substance abuse, and avoidant personality
disorder. Assessment and treatment planning must take into account the presence of these
co- occurring conditions.Personality and Life Events
As noted in Chapter 4, diathesis– stress models have been proposed to explain the etiol-
ogy and persistence of anxiety in general which, of course, are directly applicable to
GAD (e.g., Barlow, 2002; Chorpita & Barlow, 1998). In their earlier cognitive model
of generalized anxiety, Beck et al. (1985) proposed a diathesis– stress perspective in
which low self- confidence and perceived inadequacy in specific areas of functioning
are cognitive- personality diatheses that precipitate a state of chronic anxiety when trig-
gered by an event that represents a threat to the individual’s physical or psychological
survival.
In Chapter 4 we discussed a number of personality diatheses that have been impli-
cated in the development of anxiety and, by extension, GAD. Negative affectivity (NA)
has consistently emerged as the most important latent construct in factor- analytic stud-
ies of GAD. Although few studies have focused on the development of GAD specifically
(Hudson & Rapee, 2004), retrospective studies and research on anxiety more generally
suggests that high NA, neuroticism, or negative emotionality are personality diatheses
in GAD (L. A. Clark, Watson, & Mineka, 1994). In support of this contention, a
recent large twin study found that neuroticism had a substantially greater impact on
increasing risk for GAD than any other psychiatric disorder (Khan, Jacobson, Gard-
ner, Prescott, & Kendler, 2005). High trait anxiety has been considered practically
synonymous with GAD to the point where it has been suggested that GAD may be
“a relatively pure manifestation of high trait anxiety (Rapee, 1991, p. 422). Barlow