Melbourne School of Psychological Sciences - Theses
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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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ItemAssessing the relationship between executive function, coping, stress, depression, anxiety and quality of life in multiple sclerosis( 2014)Background: Compared to healthy controls, people with multiple sclerosis (PwMS) use fewer adaptive and more maladaptive coping strategies when managing stressors and they experience higher rates of depression, anxiety and adjustment disorders. In addition, PwMS experience a high prevalence of cognitive impairment, including executive dysfunction, which has been linked to depression and anxiety. Aims: The current study examined the relationship between executive function, coping strategy use and psychosocial adjustment outcomes including stress, depression, anxiety and quality of life (QoL) in PwMS. The research assessed i) the ability of coping strategies and executive function to predict maladaptive and adaptive adjustment outcomes, and ii) the relationship between executive function and coping and whether there is a moderating and mediating relationship of different coping strategies between executive function and psychosocial adjustment in PwMS. Methods: Participants (N=107) with relapsing remitting or secondary progressive multiple sclerosis were administered tasks of executive function and completed self-report measures of stress, depression, anxiety, QoL and coping. Results: Consistent with expectations, stress, depression, anxiety and QoL were predicted by adaptive and maladaptive coping styles. Similarly, coping strategies, total coping and an adaptive coping index were predicted by tasks of executive function. Lower scores on tasks of executive function best predicted higher use of maladaptive strategies, but also adaptive strategies, while higher scores were limited in their ability to predict adaptive coping strategies. Tasks of executive function that most often predicted coping strategies included tasks of working memory, cognitive flexibility, information processing and attention. However, contrary to expectations, there was limited support for a relationship between tasks of executive function and psychosocial adjustment outcomes. An indirect relationship was found between executive function performance and adjustment through individual maladaptive coping strategies and adaptive coping strategies, as well as for an index of adaptive coping. Higher executive function performance was related to better adjustment via lower venting and behavioral disengagement, as well as higher scores on the adaptive coping index, whereas lower executive function performance was related to better adjustment via higher growth and acceptance. In general, better executive function and psychosocial adjustment was associated with minimal use of adaptive coping strategies, or greater use of maladaptive coping strategies. Conclusion: Executive function and psychosocial adjustment is mediated and moderated by coping strategies used by PwMS. Well-preserved executive function provides relative protection from poorer adjustment in the presence of high maladaptive or low adaptive coping. PwMS who perform poorly on tasks of executive function benefit from using less cognitively demanding coping strategies to enhance adjustment outcomes and this area that would benefit from further research to underpin effective intervention strategies. Findings from this study will assist with development of patient resources and patient management aimed at enhancing adaptive psychosocial adjustment in PwMS.
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ItemSleep, mood, and cognitive vulnerability in adolescents: a naturalistic study over restricted and extended sleep opportunities( 2013)Introduction: It is well established that for adolescents, school days are associated with sleep restriction, and that insufficient sleep has been linked to mood disturbances. This longitudinal study assessed sleep, mood, and life stress over the school term and vacation periods with restricted and extended sleep opportunities. The relationships between objective and subjective sleep, as well as between sleep and mood were examined. A cognitive model was proposed and tested to assess whether sleep-specific (i.e., dysfunctional beliefs and attitudes about sleep) and global (i.e., dysfunctional attitudes) cognitive vulnerabilities played a role in these relationships. Methods: One-hundred and forty-six adolescents (47.3% male) aged 16.2+/-1.0 years (M+/-SD) from the general community wore an actigraph continuously for four weeks: the last week of a school term (Time-E), the following two-week vacation (Time-V), and the first week of the next term (Time-S). Social demographic information, chronotype, and cognitive vulnerabilities were assessed at Time-E. Subjective sleep, symptoms of depression, anxiety, and life stress were repeatedly measured at Time-E, Time-V, Time-S, and the middle of the subsequent school term. Regression analyses were used to explore the relationship between sleep and mood, and structural equation modelling was used to examine changes of variables over time, as well as the moderating roles of cognitive vulnerabilities. Results: Compared with school days, sleep during the vacation was characterized by later timing, longer duration, lower quality and greater variability. Daily changes in actigraphy- measured sleep over the vacation period showed linear delays in sleep timing throughout the vacation, while changes in time-in-bed were non-significant. The first vacation week was characterized by a linear decrease in total sleep time and sleep quality, and these changes stabilized during the second vacation week. Compared to vacations, school terms were associated with higher symptoms of depression, anxiety, and life stress. Poorer sleep quality, particularly poorer subjective perception of sleep quality, was significantly associated with higher symptoms of depression and anxiety. Sleep- specific cognitive vulnerability moderated the relationship between objective and subjective sleep onset latency during extended but not restricted sleep opportunity. After controlling for life stress, global cognitive vulnerability played different moderating roles in the relationship between subjective sleep and mood over school term and vacation periods. Higher global cognitive vulnerability was associated with a stronger relationship between subjective sleep and symptoms of anxiety (but not depression) during the school term, as well as with a stronger relationship between subjective sleep and symptoms of depression (but not anxiety) during the vacation period. Conclusion: Sleep, mood, and life stress changed markedly over the school term and vacation periods. Changes in sleep over the vacation suggested that the recovery from school- related sleep restriction was completed within two weeks’ extended sleep opportunity, and the average sleep duration over this period suggested that sleep requirements in adolescence may be less than conventionally described in the media and in the scientific literature. Cognitive vulnerabilities played important roles in the relationship between sleep and mood. Adolescents with higher cognitive vulnerability might be more emotionally vulnerable towards school-related sleep restriction. These findings have important implications for future studies, as well as practical implications for policies and interventions designed to improve adolescents’ wellbeing.