Melbourne School of Psychological Sciences - Theses
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ItemThe hyper-ordinary depression hypothesis, and mechanisms of cognitive rigidity in depression (or zen and art of reducing depressive cycle maintenance)( 2017)This thesis is comprised of two related parts: a theoretical inquiry into the antidepressant mechanisms of a range of Non-ordinary States of Consciousness (NSCs), alongside the development of a novel mechanistic account of depression; and a set of four empirical studies that investigated aspects of cognitive rigidity in depression that relate to this novel account. In Chapter 1, I show that various disparate induction procedures (e.g., mindfulness practice, psychedelics, brain entrainment, and endurance exercise) are associated with both the production of NSCs and the reduction of depressive symptoms. Interestingly, these NSCs have in common many core neurological, psychological, and phenomenological features that are antithetical to core features of depression. I suggest that these features of NSCs represent potential therapeutic mechanisms, and that the production of certain NSCs mediates the reduction in depressive symptoms. I argue that two related superordinate features underlie these changes – enhanced Receptivity (e.g., perceptual, particular, absorbed, suggestible, flexible, open) and enhanced Projectivity (e.g., self-efficacious, intimate, relational, self-transcendent), that together represent elevated Interdependence between the individual and the world. In contrast, I argue that numerous features of depression appear to represent a fundamental deficiency in Interdependent processing, and that this deficiency extends into the most basic level of minimal subjectivity, representing a global qualitative change that satisfies criteria for an altered state of consciousness. Consequently, I argue that depression is associated with a ‘Hyper-ordinary’ state of consciousness. I suggest that the degree to which an NSC can reduce depression is a function of the degree to which Interdependent processing occurs within the state, and endures thereafter. Chapters 2, 3, and 4 report on a set of four empirical studies that investigated cognitive abnormalities in depression associated with the Receptivity aspect of the Hyper-ordinary account of depression. These tasks explored the link between depressive symptoms and three related processes that fall under the rubric of ‘cognitive flexibility’ – the ability for unexpected information to gain access to awareness; the ability to generate divergent representations for that information; and the ability to abandon extant representations in favour of those that are more compatible with unexpected information. As depression is associated with various forms of cognitive rigidity, including biased beliefs and interpretations that resist change, these studies investigated processing abnormalities in depression that might account for such rigidities. Additionally, as cognitive rigidity in depression is typically confined to specific forms of information processing, the tasks all employed stimuli that are highly relevant to the level of construal, the thematic content, and the rhetorical mode of depressotypic thinking, thereby increasing their sensitivity to detect differences, and their ability to reveal potential therapeutic targets. Results showed that depressive symptoms were related to slower access to awareness for unexpected positive information (Chapter 4), deficits in producing diverse categories of response, with no relation to the total number of responses generated (Chapter 3), and deficits in updating interpretations, regardless of whether updating resulted in a more positive or negative interpretation (Chapter 2). Together, this thesis offers a novel account of the depression experience, argues for a set of plausible therapeutic candidates for the antidepressant effects of certain NSCs, and reports on three novel tasks that probe ecologically relevant features of cognitive rigidity in depression, thereby revealing novel therapeutic targets. The picture of depression that emerges from the theoretical account is of a profoundly isolated state characterised by a fundamental deficit in the individual’s susceptibility to be affected by their context, and the perception that one’s context cannot be affected by the individual. The empirical studies show how this deficiency relates to the diminished influence of contextual factors over interpretations and expectations in depression. The hope is that this work can improve and extend the current understanding of depression and its causes, and lead to new methods of recovery.
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ItemPsychological and neurobiological mechanisms underpinning chronic tinnitus( 2017)Chronic tinnitus, the phenomenon of a ringing, buzzing or hissing type sound in the ears or head is a prevalent health condition affecting 10-15% of the general population (Henry, Dennis, & Schechter, 2005a). It can have significant negative effects on an individual’s health and wellbeing and is associated with significant economic burden (Maes, Cima, Vlaeyen, Anteunis, & Joore, 2013; Tyler & Baker, 1983). At present, there is no cure for chronic tinnitus, likely due to the lack of consensus regarding the mechanisms maintaining the presence or impact of chronic tinnitus on individuals experiencing this condition. This thesis aimed to determine if psychological factors, and associated neural networks, could be maintaining awareness of the tinnitus sound and the severity of its impact. To achieve this objective, four studies were conducted utilising meta-analytic, questionnaire, cognitive and neuroimaging techniques. The first study comprehensively and systematically reviewed current literature regarding the psychological functioning of adults with chronic tinnitus. Results suggest that a heterogeneous array of psychological functions may be involved in the experience of chronic tinnitus, particularly emotional and cognitive functions, with meta-analyses providing consistent evidence for a role of reduced emotional wellbeing in both the presence and impact of chronic tinnitus. Study 2 and 3 further investigated the role of emotional and cognitive factors respectively in chronic tinnitus. Specifically, Study 2 investigated possible interactions between psychological factors and the vicious cycle of hypervigilance to the tinnitus sound in a heterogeneous community sample of 81 adults with chronic tinnitus. While analyses replicated the presence of the vicious cycle, this was conditional on the experience of depressive symptoms. Study 3 aimed to determine the contribution of cognitive functioning to chronic tinnitus. Compared to healthy-hearing individuals (n=26) people with chronic tinnitus (n=26) showed significant impairments in cognitive control, inhibitory control and increased symptoms of depression, with depressive symptoms and cognitive control successfully discriminating between people with and without chronic tinnitus. Combined, these studies suggest that disruption of specific large-scale neurocognitive networks proposed to underpin a range of psychological and cognitive symptoms; particularly those associated with depression may also underpin chronic tinnitus. As such, the final study of this thesis investigated the functioning of our stable neurocognitive networks, specifically the cognitive control network, in people with chronic tinnitus (n=15) and matched controls (n=15). While both groups successfully engaged the cognitive control network, the chronic tinnitus group exhibited subtle disruptions to a core node of this network, namely the right middle frontal gyrus, revealing both attenuated activation during cognitive engagement. This region also showed decreased connectivity with a node of the salience network, the right anterior insula, and increased connectivity with nodes of the autobiographical memory network, namely left posterior cingulate cortex and left medial prefrontal cortex. Together, the results of this thesis identify a failure in the process of attention-switching and the associated neurocognitive networks as a core mechanism underpinning the persistent awareness and pervasive impact of chronic tinnitus. This provides a novel framework, the Attention-Switching Model, for investigating both the experience of tinnitus, and potential treatments to help people with chronic tinnitus.
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ItemImproving depressive symptoms in adults with vision impairment: a trial of evidence-based ‘Problem-Solving Treatment' integrated within low vision rehabilitation services( 2017)Depression is exceedingly prevalent in people with vision impairment (VI), which further exacerbates vision-related functioning, disability and quality of life when left untreated.1-5 Up to 43% of people with VI experience depressive symptoms,6-11 although only one fifth of those receive psychological intervention.11 12 The main objective of this thesis was to evaluate the feasibility, effectiveness and implementation of evidence-based Problem-Solving Treatment for Primary Care (PST-PC) integrated into low vision rehabilitation (LVR) services. In this model, LVR staff were trained to deliver PST-PC via telephone to adult clients identified as showing depressive symptoms. To achieve the overall study objective, a multi-phase, mixed-methods approach was undertaken. In Phase 1, the evidence-base to support the integration of staff-delivered PST-PC in LVR services was delineated by conducting a review of the literature on depression and VI and a systematic review of the effectiveness of problem-solving interventions in this population. The findings underscored the need for pragmatic trials with longer-term follow-up to better understand the suitability of evidence-based problem-solving interventions delivered in routine LVR practice. In Phase 2, the feasibility, acceptability and preliminary data for the effectiveness of PST-PC was investigated. Fourteen LVR staff were trained to deliver PST-PC following a 2-day training workshop and training cases under psychologist supervision. Training cases were 18 LVR clients who received 6 to 8 sessions of PST-PC and participated in a single-group pre-post intervention study. Post intervention, 67% of client participants demonstrated a clinically significant change (CSC; >5-point reduction on the Patient Health Questionnaire-9 (PHQ-9)) in depressive symptoms. PST-PC was found to be highly acceptable to clients with 83% reporting that they were very satisfied with PST-PC. Concerns were raised by both staff and clients regarding telephone delivery and the client retention rate for PST-PC was low (60% completed <6 sessions). The main objective of Phase 3 was to investigate the clinical and cost-effectiveness of this model using a pragmatic, two-arm randomised controlled trial. Adult LVR clients with depressive symptoms (PHQ-9 score >5) were recruited from 28 LVR centres in Australia and randomised to receive PST-PC plus usual care (N=81) or usual care alone (N=82; referral to a general practitioner). In the intention-to-treat (ITT) analysis of the primary outcome (reduced depressive symptoms at 6 months on the PHQ-9), a large treatment effect was found (Cohen’s d (d) = -0.81, 95% CI -1.15 to -0.46) and 40% of the intervention group achieved a CSC compared to 14% of controls (odds ratio (OR) 5.72, 95% CI 1.61 to 20.36). Treatment effects were not maintained at 12 months in ITT analysis, but a significant group difference was found using the per-protocol sample (completed >4 sessions; d=0.59, 95% CI -1.09 to -0.08). ITT analysis of the secondary outcomes found greater improvements in HRQoL (Assessment of Quality of Life; d=0.39, 95% CI 0.05 to 0.72) and vision-specific distress (Impact of Vision Impairment Questionnaire; d=0.40, 95% CI 0.07 to 0.73) in the intervention group at 6 but not at 12 months. The PST-PC model was cost-effective according to commonly used willingness-to-pay thresholds in Australia (incremental cost effectiveness ratio: AU$40,386 (bootstrapped 95% CI: 20,580 to 355,190) per quality-adjusted life years gained). The aim of Phase 4 was to investigate and explore contextual factors associated with implementation of PST-PC in this setting. Given the low rate of participant retention with PST-PC in the RCT (79% completed <6 sessions), pre-treatment demographic, clinical and psychological predictors associated with early termination were investigated. 81 participants randomised to the intervention arm completed baseline and 6-month follow-up telephone assessments. Early termination was associated with being single (OR=8.77, 95% CI 2.15 to 35.66, p=0.002), having low perceived adequacy of social support (OR=0.48, 95% CI 0.30 to 0.75, p=0.001) and low acceptance of vision loss (OR=0.72, 95% CI 0.54 to 0.96, p=0.027). Staff perspectives on the barriers and facilitators to PST-PC delivery were also explored in Phase 4. Guided by theoretical frameworks that seek to evaluate implementation research,13 14 22 key project staff participated in semi-structured qualitative interviews. Prominent barriers to delivery were a lack of role recognition for PST-PC practitioners (n=32), perceived unmet client expectation with PST-PC (n=28) and dissatisfaction with telephone-delivery (n=27). Facilitating factors included a recognised need for evidence-based psychological services (n=28), clients experiencing benefits in early sessions (n=38) and comprehensive PST-PC training (n=36). In summary, this thesis supports the feasibility, clinical and cost-effectiveness of this integrated model for reducing depressive symptoms experienced by people attending Australian LVR centres. Strategies to improve retention with PST-PC are needed to ensure sufficient numbers achieve longer-term clinical benefit. Future research should also give attention as to whether staff-delivered PST-PC is scalable (or sustainable) and to developing services which are accessible to those who do not utilise LVR services (e.g. collaborative care models).