Melbourne School of Psychological Sciences - Theses
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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.
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ItemNeighbourhood disadvantage and internalising symptoms in adolescents: the mediating role of stressful life events, temperament, and maternal aggression( 2013)Purpose of the study: Disadvantaged neighbourhoods are associated with increased risk for anxiety and depression in adolescents. However the mechanisms for this relationship are not fully understood. Using a longitudinal design, I investigated whether several potential mediators, including stressful life events, maternal aggressive, dysphoric and positive behaviour, and adolescent temperament (Surgency, Negative affectivity, Effortful Control, Affiliation), could help explain the relationship between neighbourhood disadvantage and symptoms of anxiety and depression in early- to mid-adolescence. Method: A community sample of 245 adolescents and their parents participated in a range of assessments at baseline (age approximately 12-13 years old), including an observational assessment of parent-adolescent interactions, and a battery of adolescent-rated questionnaires. Neighbourhood disadvantage was assessed by combining Postal Area data collected during this first wave of assessment with a measure of disadvantage called the Socio-Economic Indexes For Areas (SEIFA) developed by the Australian Bureau of Statistics Adolescents were followed-up approximately 4 years later and completed questionnaires assessing depressive and anxious symptoms. Results: Analyses revealed that adolescents from disadvantaged neighbourhoods were more likely to report a greater number of stressful life events, and depressive and anxious symptoms. They were also more likely to score higher on temperament measures of Negative Affectivity, and lower on measures of Surgency and Effortful control. Mothers from disadvantaged neighbourhoods were more likely to display aggressive and dysphoric behaviour for longer periods, and positive behaviour for shorter periods, however no differences were detected in regard to the frequency of these behaviours. Mediational analyses using a bootsrapping approach determined that stressful life events and three temperament dimensions (low Surgency, low Effortful Control, high Negative Affectivity) significantly mediated the relationship between neighbourhood disadvantage and symptoms of anxiety and depression at baseline. Stressful life events and maternal aggression significantly mediated the relationship between neighbourhood disadvantage and change in depressive and anxious symptoms from baseline to follow-up. Conclusion: The research reported in this thesis provides evidence that disadvantaged neighbourhoods differ from less disadvantaged neighbourhoods in several different ways. In addition, various factors were found to partially mediate the relationship between neighbourhood disadvantage and anxiety and depression at different periods during adolescence. Temperament appears to be important earlier in adolescence, maternal affective behaviour seems to be important during mid- to later-adolescence, while stressful life events appear to act throughout adolescence. These findings suggest that the neighbourhood environment is likely to influence adolescents both directly, and indirectly through its effects on more proximal and individual risk factors. It was concluded that prevention and intervention programs targeting a range of risk factors in adolescents from disadvantaged neigbourhoods could be particularly effective at reducing the prevalence of internalising disorders in adolescents.
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ItemMood and anxiety outcomes in adolescents born with extremely low birthweight or extremely preterm: prevalence and neuroanatomy( 2012)Preterm birth is associated with poor outcome in a range of domains, which can persist into adolescence and beyond. This may include poor mental health outcomes, and particularly, anxiety and depressive symptoms. To date, studies of mood and anxiety outcomes in preterm groups have mainly used dimensional measures of symptoms; only a handful employ clinical diagnostic instruments and these largely focus on recent symptoms. Our understanding of the prevalence of clinically diagnosable disorders is consequently limited, particularly in late adolescence and for those born since 1990. Prematurity at birth can also have a significant and longstanding impact on brain development. An extended medial network, including the hippocampus, amygdala, and medial prefrontal cortex, is implicated in emotion regulation, as well as clinical mood and anxiety disorders. Hippocampus, amygdala, and prefrontal structure may be altered in preterm samples, but potential relationships between these brain regions and emotional outcomes are yet to be explored in preterm survivors. This study aimed to address these limitations in the current literature by i) characterising mood and anxiety outcomes in adolescents born extremely low birthweight or extremely preterm (ELBW/EP), ii) characterising the structure of regions in the extended medial network, and iii) investigating the relationships between these outcomes and brain structure. A number of specific hypotheses arose from this research question. Firstly, it was expected that the ELBW/EP group would report more recent symptoms, more frequently meet diagnostic criteria for current or past disorder, and more strongly endorse personality traits associated with anxiety and depression than a normal birthweight (>2500g; NBW), full-term (>36 weeks; FT) control group. Secondly, it was expected that ELBW/EP participants may have smaller hippocampus, amygdala, and ventromedial prefrontal cortex volumes, and thinner ventromedial prefrontal cortices, than NBW participants. Finally, it was predicted that structural reductions in these regions of interest would be associated with greater mood and anxiety symptoms, and a history of clinically diagnosable disorder, in ELBW/EP and NBW participants. This study assessed 215 ELBW/EP and 157 NBW adolescents who were born in 1991 and 1992 in the state of Victoria, Australia. Participants from a prospective geographical cohort were followed up at age 18 and completed measures of mood and anxiety symptoms and disorders (including questionnaires and a structured clinical interview), as well as personality traits. Participants also underwent structural MRI scanning, and cortical and subcortical brain volumes were generated using FreeSurfer (v5.0). Unexpectedly, there was no elevation in clinically relevant recent or lifetime history of depression or anxiety in the ELBW/EP group. Although mood and anxiety disorders were more prevalent in females overall, there was no interaction between group and gender. The ELBW/EP group had disproportionately smaller bilateral hippocampus volumes and left amygdala volumes than controls, and the ventromedial prefrontal cortex was proportionately larger and thicker in the ELBW/EP group than the NBW group. Recent mood and anxiety symptoms were not well predicted by any of the neuroanatomical variables of interest. Despite this, lifetime history of a mood or anxiety disorder was associated with smaller left vmPFC volumes. Further analyses indicated this pattern was apparent in those with a history of anxiety disorder but not mood disorder. Group did not moderate these findings. Assessment of ELBW/EP adolescents’ self-reported mood and anxiety outcomes revealed an encouraging picture. Although extremely low birthweight or extreme prematurity was associated with altered structure of regions in the extended medial network, these alterations appeared to have limited relationship with outcomes. These findings contribute to the literature by examining older adolescent mood and anxiety outcomes and using high field-strength neuroimaging. The implications for preterm survivors and the relevance of brain structure to mood and anxiety outcomes in this age group are considered.