A test of the cognitive content specificity hypothesis in depression and anxiety
Introduction
Research has consistently demonstrated that self-report measures of anxiety and depression are strongly interrelated in both clinical and non-clinical samples (Clark & Watson, 1991; Costa & McCrae, 1992; Schniering & Rapee, 2004), and significant comorbidity between mood and anxiety disorders have been extensively documented (Finch, Lipovsky, & Casat, 1989; Greenberg & Beck, 1989; Watson, Clark, & Carey, 1988). However, Bruch, Mattia, Heimberg, and Holt (1993), argue that differentiation of the unique factors associated with specific emotional disorders enhances understanding of their aetiology, course, exacerbation and treatment, and many argue that anxiety and depression should be considered conceptually distinct constructs (Clark, Beck, & Stewart, 1990; McGrath & Ratliff, 1993). However, differentiation research in anxiety and depression has generally yielded inconsistent patterns (Beck, Brown, Epstein, & Steer, 1988; Greenberg & Beck, 1989; Ingram, Partridge, Scott, & Bernet, 1994), with some studies drawing a distinction between the two disorders on a symptomatic versus cognitive basis (e.g., Ahrens & Haaga, 1993; Watson et al., 1988), with little consensus as to which distinction proves the more robust.
One of the most prominent cognitive theories of differentiation is Beck's (1976) cognitive content specificity hypothesis (CCSH), which suggests that specific cognitive content is associated with specific psychological disorders. Such differences in cognitive content reportedly differentiate between anxiety and depression, both symptomatically and diagnostically (Cho & Telch, 2005). However, a number of studies have emerged providing inconsistent findings on the CCSH (e.g., Beck, Benedict, & Winkler, 2003; Beck & Perkins, 2001; Seigert, Walkey, & Taylor, 1992), offering only partial support for the specificity model (Greenberg & Beck, 1989; Laurent & Stark, 1993; McDermut & Haaga, 1994). Clinical and empirical overlap between anxiety and depression has further complicated research efforts to differentiate between these disorders, such that diagnostic comorbidity may also potentially inflate depression scores on measures such as the Beck depression inventory (BDI; Rudd & Rajab, 1995).
A review of the literature reveals that cognitive specificity researchers tend to be divided into competing camps regarding statistical design—a group comparative versus correlational design. For instance, Clark, Beck, and Brown (1989) found that cognitive content specificity is evident in pure states of anxiety and depression, however, Ingram, Kendall, Smith, Donnel, and Ronan, (1987); (see also Jolly & Dykman, 1994) recommend that instead of a group-comparative approach, a correlational design should be used in which cognitive and affective states are measured as continuous variables. They argue that this approach can provide an accurate test of cognitive content specificity in the more usual mixed emotional states. As such, the present study will adopt a correlational design within a depressed sample and as such will incorporate the natural covariation between the mood states of anxiety and depression. The aim of this study is to partially test the CCSH within a clinical population, and to investigate specificity in depression with two cognitive constructs and two indices of symptomatology (i.e., BDI and BAI). Fig. 1 summarises the hypotheses tested.
Earlier research conducted with the CCSH has incorporated the use of only a sole cognitive construct in mostly student and/or non-clinical populations (Seigert et al., 1992). It is therefore anticipated that the implementation of this design will strengthen the test efficacy of the CCSH by including a clinical population and incorporating two cognitive constructs.
Section snippets
Participants
Participants included 61 males and 74 females (; mean ; mean completed ), recruited through local media releases. A small proportion of participants (15%) were referred by general practitioners or treating psychiatrists. Participants were included if diagnosed according to DSM-III-R (American Psychiatric Association, 1987) diagnostic criteria as suffering from major depressive episode, dysthymia, depressive disorder not otherwise specified or major
Results
Two standard multiple regression analyses were performed between (i) the BDI as the dependent variable (DV) and the ATQ and the ASSQ as independent variables (IVs); and (ii) the BAI as the DV and the ATQ and the ASSQ as IVs. Analyses were performed using SPSS REGRESSION, with an assist from SPSS FREQUENCIES for evaluation of assumptions.
Examination of the data revealed that five cases contained missing values, and were subsequently dropped from the analysis, resulting in a cases-to-IV ratio of
Discussion
The present results revealed that the ATQ was the sole significant predictor of the BDI scores, however it did not significantly predict BAI scores. Conversely, the ASSQ was found to be the sole significant predictor of the BAI scores, but not BDI scores. These findings support the hypotheses that depressive cognitions would be specifically related to, and predictive of, depressive (but not anxiety) symptoms, and anxiety cognitions would be specifically related to, and predictive of, anxiety
Acknowledgement
This project was partially supported by a Grant from the ARC. We would like to thank Dr. Free for his help.
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