Cognitive-Behavior Therapy (CBT) for Panic Disorder: Relationship of Anxiety and Depression Comorbidity with Treatment Outcome

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Research evaluating the relationship of comorbidity to treatment outcome for panic disorder has produced mixed results. The current study examined the relationship of comorbid depression and anxiety to treatment outcome in a large-scale, multi-site clinical trial for cognitive-behavior therapy (CBT) for panic disorder. Comorbidity was associated with more severe panic disorder symptoms, although comorbid diagnoses were not associated with treatment response. Comorbid generalized anxiety disorder (GAD) and major depressive disorder (MDD) were not associated with differential improvement on a measure of panic disorder severity, although only rates of comorbid GAD were significantly lower at posttreatment. Treatment responders showed greater reductions on measures of anxiety and depressive symptoms. These data suggest that comorbid anxiety and depression are not an impediment to treatment response, and successful treatment of panic disorder is associated with reductions of comorbid anxiety and depressive symptoms. Implications for treatment specificity and conceptual understandings of comorbidity are discussed.Psychiatric comorbidity is typically defined as the co-occurrence of two or more psychiatric disorders within the same individual (Maser and Cloninger 1990). Comorbidity research is particularly important because the majority of individuals presenting for treatment for an Axis I anxiety or mood disorder have at least one additional anxiety or mood disorder diagnosis (e.g., Brown et al. 1995; Brown and Barlow 1992, 1995; de Ruiter et al. 1989; Sanderson et al. 1990). For individuals seeking treatment for panic disorder, comorbidity rates for Axis I disorders generally range from 51% to 69% with some of the larger studies suggesting that estimates are approximately 60%, with generalized anxiety disorder (GAD), social phobia, and depression being the most frequently assigned disorders (Brown and Barlow 1992; Brown et al. 1995, 2001a; Sanderson et al. 1990; Tsao et al. 1998, 2002).Studies examining treatment outcome for panic disorder with anxiety and depression comorbidity have produced mixed results. While a number of studies have suggested that the presence of comorbid diagnoses, particularly depression, is associated with less improvement on some measures of panic symptoms (i.e., achieving substantial improvement in panic symptoms or attaining “panic-free” status) (Brown et al. 1995; Steketee et al. 2001; Tsao et al. 1998), these findings have not been consistent. For example, Tsao et al. (2002) found no differences between anxious and depressive comorbid and non-comorbid groups at posttreatment on panic severity, agoraphobia severity, and endstate functioning, and similar findings have been evident when examining comorbid depression, specifically (McLean et al. 1998). In fact, some comorbidity, such as social phobia, may be associated with better treatment outcome for panic disorder (Brown et al. 1995). The mixed outcomes from these studies suggest that no stable relationship between certain types of comorbidity and panic disorder treatment has yet emerged. This may be due in part to variability in assessment measures, as well as the relatively small sample sizes in previous studies (e.g., Tsao et al. 1998, 2002).A more consistent and encouraging finding is that, overall, comorbid diagnoses show significant reductions over the course of treatment, even though these concerns are not the focus of the treatment provided. With the exception of one study (McLean et al. 1998) that found depressive symptoms changed only at a rate similar to changes expected from the passage of time, results from Brown et al. (1995) and two other studies (Tsao et al. 1998, 2002) report significant reductions in the rates of comorbid GAD, social phobia, and depression from pre- to posttreatment.The current study aims to replicate and extend the research on comorbidity in panic disorder by examining the relationship of comorbid anxiety and unipolar mood disorders to treatment outcome. The strengths of this study include (a) a large sample size generated from four study sites, (b) both clinician-rated and self-report measures focusing on panic and associated symptoms, (c) carefully monitored adherence to a manualized CBT protocol for panic disorder, and (d) diagnostic assessments conducted by independent evaluators (IEs). Although the panic disorder and comorbidity literature has not produced consistent findings upon which to base hypotheses, given the data from relatively large samples in previous studies, we hypothesize that rates of comorbidity will approximate those previously reported in studies where panic disorder is the principal diagnosis, with GAD, social phobia, and major depressive disorder (MDD) being the most common comorbid diagnoses. Furthermore, we hypothesize that comorbidity will not be associated with a decreased likelihood of achieving treatment response, and overall rates of comorbid diagnoses will decrease following treatment.

Publication Date

January 2010

Publication Title

Journal of Psychopathology and Behavioral Assessment



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