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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ItemThe SENSE Study (Sleep and Education: learning New Skills Early): long-term outcomes of a randomised controlled trial of a cognitive-behavioural and mindfulness-based group sleep intervention to prevent depression and improve anxiety in at-risk adolescents( 2019)Objective: Depression is one of the most common and debilitating mental health problems and its incidence dramatically increases during adolescence. Accumulating evidence suggests that adolescent depression can be prevented with psychosocial interventions, but there is still insufficient evidence to support their widespread implementation. Notably, there is a need for randomised controlled trials of novel interventions that are delivered to community-based adolescents identified to be at-risk for developing depression (i.e., targeted prevention) rather than the general adolescent population (i.e., universal prevention). Improving sleep represents a promising and innovative therapeutic target for the prevention of adolescent depression. Not only are sleep problems, including insufficient and poor-quality sleep, common during adolescence, they also tend to precipitate the onset of depression. Further, sleep interventions may be especially effective if they are delivered to adolescents experiencing anxiety. Anxiety, particularly generalised anxiety, and sleep problems often co-occur, and anxiety is also a risk factor for the development of depression. Evidence from a small but growing number of studies indicates that multicomponent cognitive-behavioural and mindfulness-based sleep interventions can improve sleep in adolescent samples. However, few studies have investigated depression and anxiety outcomes, particularly using randomised controlled designs, active control comparison conditions, extended follow-up periods, a multi-method assessment of sleep (i.e., subjective and objective measures) and mental health (i.e., diagnosis and symptoms) outcomes, and in community-based samples. Notably, no randomised controlled trial has investigated whether a sleep intervention can prevent the first onset of major depressive disorder (MDD) in adolescents. The current study was designed to address these gaps in the literature. The primary aim of the study was to investigate the long-term efficacy of a seven-week cognitive-behavioural and mindfulness-based group sleep intervention for the targeted prevention of first onset MDD and improvement of depressive symptoms over a two-year follow-up period in community-based adolescents experiencing concurrent high levels of anxiety symptoms and sleep problems (i.e., ‘at-risk’ for depression). Given the association between sleep and anxiety, notably generalised anxiety disorder (GAD), and dearth of adolescent sleep intervention studies investigating anxiety outcomes, the secondary and exploratory aim of the study was to investigate the long-term efficacy of the sleep intervention for preventing the incidence of GAD and improving anxiety symptoms over a two-year follow-up period. Importantly, the study aimed to demonstrate that any beneficial effects to depression and/or anxiety outcomes occurred via the putative mechanism of improvements to subjective and objective indices of sleep. As best can be determined, the research reported in this thesis represents the only attempt to date to prevent first onset MDD by improving sleep in an adolescent sample, and the only randomised controlled trial of an adolescent sleep intervention to examine anxiety outcomes over a two-year follow-up period. It was predicted that, compared to adolescents allocated to the active control (study skills) intervention, adolescents allocated to the sleep treatment intervention would: show greater improvements in subjective and objective indices of sleep (i.e., reduced sleep onset latency, increased total sleep time, better overall sleep quality, and reduced weekday bedtime intra-individual variability and weekday-to-weekend bedtime shift) immediately following the intervention and over the two-year follow-up period; be less likely to develop first onset MDD during, and would report lower levels of depressive symptoms at, the two-year follow-up (primary outcomes); and would be less likely to develop new onset GAD during, and would report lower levels of anxiety symptoms at, the two-year follow-up (secondary outcomes). Further, it was predicted that any beneficial long-term effects for depression and anxiety outcomes (i.e., lower incidence of MDD or GAD and/or reduction in depressive and anxiety symptoms) would be significantly mediated by improvements in sleep associated with the sleep treatment intervention (i.e., sleep improvements immediately post-intervention and/or over the two-year follow-up period). Methods: Participant recruitment and eligibility assessments occurred from January 2013 to June 2014. A school-based screening (n = 1491) was conducted at 23 secondary schools (14 Government, 4 Catholic, 5 Independent) in metropolitan Melbourne, Australia, to identify community-based adolescents with high levels of self-reported sleeping problems (score > 4 on the Pittsburgh Sleep Quality Index; PSQI) and anxiety symptoms (score > 32 males/ > 38 female on the Spence Children’s Anxiety Scale; SCAS). Consenting participants who met screening criteria (n = 218) completed semi-structured diagnostic clinical interview (Kiddie-Schedule for Affective Disorders and Schizophrenia for school-age children-Present and Lifetime version; K-SADS-PL) at the University of Melbourne, primarily to exclude individuals (n = 30) with a lifetime history of MDD, consistent with the study’s aim to prevent first onset depression. Eligible participants (n = 144) were randomised (1:1 allocation on an individual basis, and conditions were balanced for age, gender and presence or absence of current anxiety disorder at baseline) to either a seven-week, face-to-face, multicomponent cognitive-behavioural and mindfulness-based group sleep improvement treatment intervention (Sleep SENSE; n = 71) or an attention-matched active control study skills intervention (Study SENSE; n = 73). The Sleep SENSE intervention aimed to address common sleep problems including insufficient sleep duration, prolonged sleep onset, and variability in sleep timing, and included anxiety management components to assist with managing anxiety during the pre-sleep period. Mental health and sleep were assessed using: the K-SADS-PL (for MDD and GAD diagnosis); the Center for Epidemiologic Studies-Depression scale (CES-D; depressive symptoms); the SCAS (anxiety symptoms); the PSQI (self-reported sleep onset latency, total sleep time, overall sleep quality); and week-long actigraphy with sleep diary (objective sleep onset latency, total sleep time, weekday bedtime intra-individual variability, and weekday-to-weekend bedtime shift). Assessments occurred on three occasions–pre-intervention, post-intervention, and two-years after the completion of the intervention. All outcome assessments were administered by researchers who were blind to participants’ intervention assignment. Statistical analyses: All analyses used a modified intention-to-treat approach. Specifically, the final analysed sample (n = 122, sleep treatment n = 62, control intervention n = 60; 60% female; M age = 14.5 years, SD = 0.95, range 12.04 to 16.31 years) included participants who were eligible for and started the interventions, including those who dropped out of the interventions or were lost to follow-up (n = 13) but excluded participants who were identified as ineligible after randomisation (n = 2) and those who were randomised but never started the interventions (sleep treatment n = 10, control intervention n = 10). Latent growth curve modelling with multiple mediation analysis was used to test the effect of condition (i.e., sleep treatment or control intervention) on the long-term depression (i.e., presence or absence of MDD diagnosis, and severity of depressive symptoms) and anxiety (i.e., presence or absence of GAD diagnosis, and severity of anxiety symptoms) outcomes via improvements in the seven sleep variables immediately post-intervention (i.e., ‘initial status’ which was centred at the post-intervention time point) and over the two-year follow-up period (i.e., average linear ‘rate of change’ scaled to represent change per year). That is, the latent growth process of a sleep variable (i.e., the latent variables of initial status and rate of change) was used the mediator in the tested models. In total, 28 separate models were estimated using Mplus (Version 7) software using maximum likelihood estimation with robust standard errors. Results: Regarding the primary outcomes, there was no statistical evidence that the sleep treatment intervention improved subjective or objective indices of sleep immediately post-intervention or over the two-year follow-up period, or significantly predicted the presence or absence of major depressive disorder during, or reductions in depressive symptoms at, the two-year follow-up, relative to the active control intervention. Regarding the secondary outcome, the sleep treatment intervention did not significantly predict reductions on anxiety symptoms at two-year follow-up. However, the sleep treatment intervention significantly reduced the conditional odds of having GAD during the two-year follow-up period by a factor of seven on average, relative to the active control intervention, although confidence intervals suggested a small effect. There were no statistically significant indirect effects in any of the model investigated. Regardless of condition, participants’ subjective (B = -1.77, 95% CI [-3.47, -0.07]) and objective (B = -4.53, 95% CI [-7.96, -1.10]) sleep onset latency and subjective total sleep time (B = -0.18, 95% CI [-0.31, -0.05]) decreased over time, and weekday bedtime intra-individual variability increased over time (B = 7.99, 95% CI [2.11, 13.86]). In addition, poorer subjective sleep quality (B = 1.46, 95% CI [0.38, 2.54]) and less objective total sleep time (B = -3.31, 95% CI [-6.33, -0.28]) immediately post-intervention predicted depressive symptoms at two-year follow-up, and reductions in weekday bedtime intra-individual variability over time were associated with a decreased likelihood of GAD during the two-year follow-up (B = -0.52, 95% CI [-0.86, -0.18]). Conclusions: Together, the findings do not support the long-term efficacy of a targeted multicomponent cognitive-behavioural and mindfulness-based group sleep intervention for the improvement of sleep problems and prevention of first onset major depressive disorder in a community-based sample of at-risk adolescents. However, they tentatively suggest that anxiety may be more responsive to the sleep intervention than depression. In the context of a robust study design, the findings are hypothesis-generating and raise important considerations for the design of future clinical trials investigating the role of adolescent sleep interventions on emerging psychopathology. Funding: Australian National Health and Medical Research Council Grant (APP1027076). Trial Registration: Australian New Zealand Clinical Trials Registry (ACTRN12612001177842; prospectively registered on 6th November 2012).
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ItemThe SENSE study (Sleep and Education: learning New Skills Early): postintervention effects of a randomised controlled trial of a cognitive-behavioural and mindfulness-based group sleep improvement intervention among at-risk adolescents( 2016)Objective: There is growing recognition that many adolescents obtain insufficient and/or poor quality sleep. Sleep problems are also a major risk factor for the emergence of mental health problems in adolescence. However, few studies have examined disturbed sleep as a potential mechanism in the treatment and prevention of mental health problems among adolescents. Adolescent sleep problems can be treated using a range of approaches. School-based sleep education programs, which are typically delivered to whole school classes, have been shown to have little impact on sleep behaviour or mental health. Cognitive-behavioural and mindfulness-based sleep programs, which are typically delivered to at-risk or already symptomatic adolescents, have been shown to be more effective in improving sleep and emotional distress, but studies evaluating their effectiveness have been limited in several ways, including small sample sizes and inadequate/lack of control groups. We conducted a systematic review and meta-analysis examining the efficacy of cognitive-behavioural sleep interventions among adolescents. Searches of PubMed, PsycINFO, CENTRAL, EMBASE, and MEDLINE were performed from inception to 1 May 2016. Eight trials were selected (n=234, mean age=15.24 years; female=63.18%). Main outcomes were subjective (sleep diary/questionnaire) and objective (actigraphy) total sleep time (TST), sleep onset latency (SOL), sleep efficiency (SE), and wake after sleep onset (WASO). There was a small number of randomised controlled trials (RCTs; n=3), and a high risk of bias across the RCTs; therefore within sleep condition meta-analyses were examined. At post-intervention, subjective TST improved by 29.47 minutes (95% CI = 17.18, 41.75), SOL by 21.44 minutes (95% CI = -30.78, -12.11), SE by 5.34% (95% CI = 2.64, 8.04), and WASO by a medium effect size (d = 0.59 [95% CI = 0.36, 0.82). Objective SOL improved by 16.15 minutes (95% CI = -26.13, -6.17), and SE by 2.82% (95% CI = 0.58, 5.07). Global sleep quality, daytime sleepiness, depression, and anxiety also improved. Gains were generally maintained over time. Our meta-analysis provides preliminary evidence that cognitive-behavioural sleep interventions are an effective treatment for adolescent sleep problems, producing clinically meaningful responses within active treatment conditions. Their efficacy is maintained over time, and results in significant alleviation of sleep problems and improvement in functional outcomes. However, further large-scale, high-quality RCTs are needed to confirm these findings. The aim of this thesis was to investigate the post-intervention effects of a cognitive-behavioural/mindfulness-based group sleep intervention on sleep, mental health, and cognitive style among at-risk adolescents. The study went beyond simply measuring treatment outcomes to also evaluate mechanisms of change. Based on the behavioural, cognitive, hyperarousal, and transdiagnostic models of insomnia, a number of specific mediators were hypothesised to account for therapeutic change in cognitive-behavioural and mindfulness-based sleep interventions for adolescents, including earlier bedtimes, more consistent bedtimes, increased sleep hygiene awareness, and decreased dysfunctional beliefs and attitudes about sleep, worry, rumination, pre-sleep arousal, anxiety, and depression. Method: A RCT was conducted across Victorian secondary schools in Melbourne, Australia. Adolescents (aged 12-17 years) were recruited using a two-stage procedure, consisting of an in-school screening (n=1491) followed by a diagnostic interview for those meeting screening criteria (n=218), to identify students with high levels of anxiety and sleeping difficulties, but without past or current major depressive disorder (n=144). Eligible participants were randomised into either a sleep improvement intervention (‘Sleep SENSE’) or an active control ‘study skills’ intervention (‘Study SENSE’). One hundred twenty three participants began the interventions (Female=60%; Mean Age=14.48, SD=0.95), with 60 in the sleep condition and 63 in the control condition. All participants were required to complete a battery of mood, sleep and cognitive style questionnaires, seven-days of wrist actigraphy (an objective measurement of sleep), and sleep diary entry at pre-and-post intervention. Results: The sleep intervention condition was associated with significantly greater improvements in subjective sleep (global sleep quality, sleep onset latency, daytime sleepiness), objective sleep onset latency, anxiety, pre-sleep arousal, and sleep knowledge compared with the control intervention condition, with small-medium effect sizes. Parallel multiple mediation models showed that there were bidirectional relationships between improvements in subjective sleep quality and pre-sleep arousal/global anxiety. Conclusion: The SENSE study is an efficacy trial of a selective group-based sleep intervention for the treatment and prevention of sleep and mental health problems among at-risk adolescents experiencing both sleep and anxiety disturbance. The study provides evidence, using a methodologically rigorous design, including an active control comparison condition, that a multi-component group sleep intervention that includes cognitive-behavioural and mindfulness-based therapies, can improve wakefulness in bed variables, daytime dysfunction, anxiety, pre-sleep arousal, and sleep knowledge among at-risk adolescents. The results also provide evidence that pre-sleep arousal and anxiety are particularly important for adolescents’ perceived sleep quality, and should be key targets for new treatments of adolescent sleep problems. Public Health Significance: Given the high prevalence of adolescent sleep and internalising problems, the implications of an effective adolescent sleep intervention for clinical practice and public policy are potentially significant. However, changing sleep behaviour, especially objective measures of sleep, in this age group, has been challenging. This thesis shows that the Sleep-SENSE program can improve objective and subjective indices of sleep, as well as anxiety symptoms, when compared to an active control intervention. The results also showed that reductions in pre-sleep hyperarousal represent a key psychophysiological mechanism for therapeutic improvements in subjective sleep problems among anxious adolescents, and that cognitive behavioural and mindfulness-based sleep interventions should be directed towards adolescents with vulnerability for hyperarousal. Sleep SENSE is one of the only interventions demonstrated to be efficacious in improving sleep and mental health amongst vulnerable adolescents. Furthermore, the program is likely to be cost-effective - it involves a simple screening process and a group intervention format - and could be disseminated to a wide range of clinical and non-clinical settings in primary care, mental health, adolescent health and sleep medicine, and may assist in the treatment and prevention of adolescent sleep and mental health problems. The intervention also lends itself to flexible modes of delivery (e.g., non-specialist practitioners, group settings, individual settings, school-based, internet and other e-health modes of delivery), further enhancing its translational potential.