Our conceptualization and empirical understanding of the course of depression is beginning to change. This is largely a result of recent epidemiological and clinical data that suggest depression has a chronic course for many individuals. Treatment studies for chronic depression have found that response rates are consistently less robust than in studies of acute, episodic depression. As is such, investigators have begun to examine factors that impede treatment response among these patients. One such factor is the presence of comorbid Axis-II personality disorders. This study examined the moderating effects of Depressive Personality Disorder (DPD) on treatment outcome among 680 outpatients with chronic depression. Results suggest that DPD did not serve as a prognostic indicator of worse outcome after 12 weeks of treatment or at last observation carried forward. This was a secondary analysis of the data presented by Keller and colleagues (Keller, McCullough, Klein, Arnow, Dunner, & Gelenberg, 2000).

Chronic major depressive disorder (CMDD) is a common and debilitating illness. Its pathophysiology needs further elucidation, before more effective targeted treatments can be developed for this condition. To gain a better understanding of the psychobiology of CMDD, three interconnected studies were conducted that examined the interplay between chronic depression, cortisol responses, and personality. Study 1 examined cortisol responses to the Trier Social Stress Test (TSST) in CMDD participants (n=29) as compared to healthy controls (n=28). It was hypothesized that cortisol responses would be greater in the CMDD population. Results indicated that females with CMDD had increased cortisol output compared to female controls, a pattern consistent with the hypothesis. However, males with CMDD had decreased cortisol responses compared to male controls. These results suggest that cortisol responses to social stress are altered in those with CMDD; however, females and males experience fundamentally different changes. Study 2 examined moderating effects of personality on cortisol responses to the TSST in those with CMDD (n=51) as compared to healthy controls (n=57). It was hypothesized that higher neuroticism and/or lower extraversion would be associated with increased cortisol responses in CMDD participants. As hypothesized, lower extraversion was associated with increased cortisol reactivity in those with CMDD but not in healthy controls. However, no association was found between neuroticism and cortisol responses. These findings could support the notion that lower extraversion is a vulnerability marker for chronic depression and thus a possible target for treatment. Study 3, evaluated the cortisol awakening response (CAR) in CMDD participants (n=27) compared to healthy controls (n=30). It was hypothesized that such awakening responses would be more pronounced in the depressed population compared to controls. Contrary to expectation, no differences were found between the groups. However, lower extraversion was associated with a lower CAR in both CMDD and healthy controls, a finding that was not anticipated a priori. These interconnected studies suggest that examining relationships between depression, cortisol responses, and personality, can assist with identifying distinct psychobiological profiles in those with chronic depression. It is proposed that this strategy will improve the likelihood of developing more targeted treatments for this population.

Chronic major depressive disorder (CMDD) is a common and debilitating illness. Its pathophysiology needs further elucidation, before more effective targeted treatments can be developed for this condition. To gain a better understanding of the psychobiology of CMDD, three interconnected studies were conducted that examined the interplay between chronic depression, cortisol responses, and personality. Study 1 examined cortisol responses to the Trier Social Stress Test (TSST) in CMDD participants (n=29) as compared to healthy controls (n=28). It was hypothesized that cortisol responses would be greater in the CMDD population. Results indicated that females with CMDD had increased cortisol output compared to female controls, a pattern consistent with the hypothesis. However, males with CMDD had decreased cortisol responses compared to male controls. These results suggest that cortisol responses to social stress are altered in those with CMDD; however, females and males experience fundamentally different changes. Study 2 examined moderating effects of personality on cortisol responses to the TSST in those with CMDD (n=51) as compared to healthy controls (n=57). It was hypothesized that higher neuroticism and/or lower extraversion would be associated with increased cortisol responses in CMDD participants. As hypothesized, lower extraversion was associated with increased cortisol reactivity in those with CMDD but not in healthy controls. However, no association was found between neuroticism and cortisol responses. These findings could support the notion that lower extraversion is a vulnerability marker for chronic depression and thus a possible target for treatment. Study 3, evaluated the cortisol awakening response (CAR) in CMDD participants (n=27) compared to healthy controls (n=30). It was hypothesized that such awakening responses would be more pronounced in the depressed population compared to controls. Contrary to expectation, no differences were found between the groups. However, lower extraversion was associated with a lower CAR in both CMDD and healthy controls, a finding that was not anticipated a priori. These interconnected studies suggest that examining relationships between depression, cortisol responses, and personality, can assist with identifying distinct psychobiological profiles in those with chronic depression. It is proposed that this strategy will improve the likelihood of developing more targeted treatments for this population.

Cognitive Behavioural Analysis System of Psychotherapy (CBASP) has been developed to treat individuals suffering from chronic depression. There is a growing evidence base to suggest that CBASP is effective for these individuals. Given these findings, it is important to understand the process of change during CBASP and how it is affected by the components of the therapy. Purpose: A systematic review and meta analysis aimed to establish whether there is evidence for one of the theoretical foundations of CBASP; that a hostile-submissive interpersonal style is associated with major depressive disorder, and in particular with chronic forms of depression, as suggested by McCullough (2000). An empirical study then aimed to investigate whether the components of CBASP are associated with symptom change for chronically depressed individuals during therapy. It also sought to examine whether individuals experienced change differently in CBASP if it was delivered without using Disciplined Personal Involvement (DPI) by the therapist. The aim of this research was to investigate the process of change within the context of CBASP for individuals receiving the therapy, and to evaluate the usefulness of a multilevel modelling approach to analysing singe-case data. Methods: The literature was systematically searched for research reporting a relationship between depression and interpersonal hostility and/or submissiveness and a meta-analysis conducted to test the strength of this relationship. An empirical study presents analyses of two datasets. The first is a multilevel modelling analysis of data from a CBASP case series, seeking to determine what role the components of CBASP have in symptom change during therapy. A single-case, multiple baseline study then examined the process of symptom change during CBASP. This study included individuals experiencing chronic depression, who completed a series of baseline observations followed by up to 20 sessions of CBASP over a six-month period. Participants were assigned to either receive manualised CBASP, or a form of CBASP without the interpersonal focus. The latter study employed mixed models to evaluate change in individuals in CBASP, and sought to evaluate this novel approach to single-case analysis. Results. The meta analytic review provided preliminary support for McCullough’s (2000) hypothesis that chronically depressed individuals tend to present as more hostile and submissive than individuals with first-episode MDD. Findings from the empirical study suggest that acquisition learning in relation to the situational analysis exercise in CBASP is associated with symptom change but not learning in relation to the interpersonal discrimination exercise. Findings from the single-case analysis, however, provided limited evidence that CBASP without the interpersonal focus is associated with less change over the first few sessions of therapy than CBASP. Multilevel modeling analysis of single cases appeared to provide a useful approach to evaluating within-individual change in therapy, compared with traditional methods such as clinically significant change indices. Discussion: The findings of this thesis provide preliminary evidence for components of McCullough’s (2000) CBASP model. The review’s results pointed to a need for more methodologically sound studies to further investigate the role of interpersonal style in the aetiology and maintenance of chronic depression. Analyses in the empirical study appeared to support the use of Situational Analysis in bringing about symptom change in therapy, but findings were mixed in relation to the interpersonal components of CBASP. The use of a small-N design with multiple baselines allowed for a preliminary analysis of the role of DPI, but incomplete data limited this analysis to the first half of therapy.