Melbourne School of Psychological Sciences - Theses
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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.
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ItemTemperament change during adolescence: Normative growth trajectories and the association of temperament change and pubertal development factors with adolescent psychopathology( 2016)Purpose of the study: This study examined the nature of temperament change during adolescence, using a longitudinal design to describe normative changes and individual heterogeneity in the developmental trajectories of traits. The study design allowed for further investigation of whether individual changes in temperament are associated with specific risk for depressive disorders. Pubertal timing and tempo were examined as developmentally salient factors that may potentially contribute to individual level changes in traits, including changes associated with depressive disorders. Method: A community sample of 245 adolescents participated in the longitudinal assessment of four temperament traits (Affiliation, Effortful Control, Negative Emotionality, Surgency), using the Early Adolescent Temperament Questionnaire, across five time points from early adolescence (mean age 11.62 years) to late adolescence (mean age 18.88 years). Univariate and multivariate latent growth modelling approaches, including latent growth models, latent class growth models and growth mixture models, were used to analyse normative and individual trajectories of temperament change. Adolescent depression was assessed via a questionnaire measure of symptoms and clinical interviewing to determine case level depressive disorders. To examine the specificity of associations between temperament and depression, questionnaire and interview measures were also used to assess adolescents’ broader risk for psychopathology, including anxiety and externalising symptoms and case level disorders. Pubertal timing and tempo were assessed during early adolescence using measures based on the Pubertal Development Scale. Results: Analyses of normative temperament trajectories revealed non-linear changes for Affiliation, Negative Emotionality and Surgency, reflecting both increases and decreases in temperament maturity during adolescence. The normative trajectory for Effortful Control showed linear decreases across adolescence. There was evidence of significant heterogeneity of temperament development, including individual differences in baseline levels of traits and in the degree and direction of change. The extent of heterogeneity was more sufficiently represented by significant individual level variance around univariate trajectories of normative change, rather than by sub-groups of individuals in multivariate models. Increased risk for depression was associated with lower baseline Surgency and Effortful Control, higher baseline Negative Emotionality and overall decreases in Affiliation, as well as relatively greater decreases in Effortful Control and slower decreases in Negative Emotionality compared with same age and gender peers. However, while specific risk for depressive disorders was associated with decreases in Affiliation during adolescence, further associations were observed between baseline levels and changes in traits with other categories of psychopathology. There was no evidence that pubertal timing and tempo are sources of temperament change during adolescence, however pubertal timing showed significant associations with adolescent psychopathology. Conclusions: This study contributes to existing literature on temperament that describes adolescence as a developmental period when normative temperament changes do not show overall increases in maturity. This study also highlights the need for further research to identify sources of temperament change during adolescence, as pubertal timing and temperament may be independent risk factors for psychopathology during adolescence. The findings add to accumulating evidence suggesting that changes in temperament influence an individual’s level of risk for adolescent psychopathology, over and above risk from baseline levels of traits. This includes evidence of temperament changes that confer specific risk for depression, including decreases in Affiliation, rather than general risk for psychopathology. Such findings may assist with targeting prevention or early intervention efforts against adolescent depression.
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ItemTuning in to teens: examining the efficacy of an emotion-focused parenting intervention in reducing pre-adolescents’ internalising difficulties( 2014)The transition from childhood to adolescence coincides with an increase in anxiety, a peak in somatic complaints, and a post-pubertal rise in depression by mid-adolescence, particularly for girls. For those affected, internalising difficulties result in considerable stress and impairment for the young person even if symptoms do not reach criteria for clinical diagnosis. Up to 50% of all adult psychological disorders have their onset during adolescence, highlighting the importance of identifying methods of prevention that are evidence-based. Emotional competence has been found to be an important protective factor for healthy social, emotional, and behavioural functioning. Both adolescents and adults with internalising difficulties show deficits in aspects of emotional competence. Research in child development suggests that parents’ emotional competence and emotion socialisation practices are related to children’s emotional functioning, including child internalising difficulties. This research has not yet been translated into intervention or prevention programs targeting parents of adolescents. The current study examined the efficacy of the Tuning in to Teens parenting program in improving emotion socialisation practices in parents of pre-adolescents and in measuring the impact on youth internalising difficulties. Grounded in emotion socialisation theory, this program teaches parents skills in responding to emotions in ways that enhance emotional competence in the young person, while also improving parent-youth communication and connectedness. A group-randomised control design was used where participants were recruited from schools and randomised into intervention and control conditions. Data were collected from 225 parents and 224 youth during the young person’s final year of elementary school (6th grade) and again, 10 months later in their first year of secondary school (7th grade). The thesis includes three studies. Study 1 reports the results of multilevel analyses, which showed participation in Tuning in to Teens resulted in significant improvements in parental emotion socialisation and reductions in youth internalising difficulties for the intervention condition. Study 2 examined moderators and mediators of program outcome. Results showed greater program effects for intervention subgroups with high pre-intervention difficulties. Parental education, income, parental internalising difficulties, parental difficulties in emotion awareness and regulation, and attendance rate did not moderate program effects. Mediation analyses supported emotion socialisation theory and showed parents who participated in the Tuning in to Teens parenting program reported improvements in emotion socialisation, which in turn was related to reductions in youth internalising difficulties. Study 3 investigated the relationship between parent emotion socialisation and youth somatic complaints. The study extended the literature on somatic complaints by being the first to consider parents’ emotional competence and emotion socialisation practices as predictors of youth somatic complaints alongside parents’ own somatic complaints. Results indicated that changes in parents’ awareness and regulation of emotion and emotion socialisation practices resulted in reduced youth somatic complaints. These findings have important implications for current aetiological models of somatic complaints and provide support for using an emotion-focused approach to enhance current treatment models of youth somatic complaints. A significant contribution of this thesis is that it presents the first randomised control trial evaluation of a parenting program that utilises research linking parents’ emotion socialisation with young people’s mental health, applying it in practice with a sample of parents of pre-adolescents. The research findings provide support for emotion socialisation theory and for using an emotion focused parenting program to prevent internalising difficulties in early adolescence.
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ItemAdolescent-onset depression: the interplay between family relationships, brain development and inflammation( 2014)Adolescence is an important life phase in which to explore psychological functioning. The emergence of depression during adolescence has been linked to aspects of both the family environment and brain developmental processes, although few studies have explored these two key variables together to prospectively determine adolescent vulnerability to depression. Consequently, the aim of the present thesis was to determine whether volume change in the pre-frontal cortex (PFC), amygdala and hippocampus partially, but significantly, mediate the effects of maternal behaviours on the onset of depression during adolescence. A secondary aim of this study was to explore a specific mechanism through which these changes in the brain may occur; specifically, systemic inflammation as marked via the production of CReactive Protein (CRP). Overall, it was expected that family interactions charaterised by higher rates and longer durations of Aggressive and Dysphoric maternal behaviours would predict the onset of clinical depression. Moreover, it was hypothesized that such maternal behaviours would predict changes in brain volume previously reported in depressed samples, as well as increased levels of CRP. Lastly, it was anticipated that elevated levels of CRP associated with more hostile maternal behaviours would partially, but significantly, mediate the relationship between parenting and structural brain development. Data from the larger Adolescent Development Study (ADS) were used to explore these aims and hypotheses. The ADS is a prospective longitudinal research study that consists of four waves of data collection, with data for this research project drawing on each of these four data collection time points in the following areas; magnetic resonance imaging (MRI) (T1, T3 and T4), family interaction tasks (T1), diagnostic assessment of mental health (T1 -T4) and saliva samples to measure inflammation (T2). As such, participants in this research comprised a smaller sub-sample of the total ADS sample population. This sub-sample consisted of N = 160 adolescents (females = 80), of which N = 32 (females = 22) received a diagnosis of clinical MDD. Path analysis techniques were used to analyse the data. The findings from the present study confirmed that maternal behaviours and changes in brain volume over time both increase vulnerability to MDD onset during adolescence. However, no evidence was found that changes in brain volume across the ages of 12 to 19 years in the PFC, amygdala or hippocampus mediated the effects of these maternal behaviours on mental health outcomes. Moreover, maternal behaviours were also found to result in detectable changes in brain volume over time, highlighting how even subtle variations in parenting behaviour influences biological development. However, when the immune system was included in these analyses, results suggested that CRP did not mediate the influence of maternal behaviours on these structural changes in the brain. The complexities of these interactions and their implications for our understanding of etiological models of depression during adolescence are considered.
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ItemDevelopment of the prefrontal cortex and its relationship to self-regulatory abilities during adolescence( 2014)Adolescence is a period of significant brain maturational changes in regions associated with self-regulation. While normative patterns of cortical thinning are postulated to underlie adaptive functioning, aberrations of this process are thought to result in poor self-regulatory abilities. This study characterises the development of three regions known to underlie regulatory processes, the anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (dlPFC) and ventrolateral prefrontal cortex (vlPFC), during adolescence. The study also examines the relationship between development of these cortical regions with three aspects of self-regulation: i. temperamental effortful control, ii. proactive and reactive forms of cognitive control, and iii. cognitive reappraisal, an adaptive emotion regulation strategy. Ninety-two adolescents (47 females) were examined longitudinally during early (mean age = 12.67), mid- (mean age = 16.42) and late adolescence (mean age = 18.78). Structural MRI scans were obtained at early and mid-adolescence, and cortical thickness of the regions of interest was measured using a semi-automated software (FreeSurfer). Effortful control (measured using the Early Adolescent Temperament Questionnaire-Revised), and proactive and reactive cognitive control (measured using a modified Stroop task), were also examined at early and mid-adolescence. Finally, cognitive reappraisal was measured at late adolescence using the Emotional Regulation Questionnaire. Linear mixed models were employed to analyse brain development between early and mid-adolescence, including sex and hemisphere effects. Subsequently, general linear and linear mixed models were employed to investigate the relationship between change in cortical thickness and change in effortful control/cognitive control over time. Finally, general linear models were employed to investigate the relationship between change in cortical thickness and use cognitive reappraisal strategies during late adolescence. Sex effects were included in all models. Findings revealed that the ACC, dlPFC and vlPFC exhibited significant reductions in cortical thickness between early and mid-adolescence across both hemispheres and sexes. Greater effortful control across time (i.e., averaged across early and mid-adolescence) was related to greater thinning of the left ACC, dlPFC and vlPFC over time, while greater proactive cognitive control across time was related to greater thinning of the right ACC. In addition, greater thinning of the left dlPFC and vlPFC was related to greater engagement in cognitive reappraisal during late adolescence in females. In relation to the development of self-regulation, greater relative increase in effortful control was related to greater thinning of the left dlPFC at trend level. However, greater relative increase in proactive control was related to less thinning of the right vlPFC, and greater relative increase in reactive control was related to less thinning of the left ACC (the latter in males alone). These findings highlight a complicated and dynamic relationship between cortical and self-regulatory development during adolescence, with different patterns of cortical maturation being advantageous for different forms of self-regulation. The importance of investigating sexual dimorphism in brain-behaviour relationships is also emphasised, as different associations were identified between cortical maturation and self-regulation in males and females. These findings suggest that early to mid-adolescence is a developmentally sensitive period for self-regulation, and provide a foundation for understanding abnormal patterns of brain development, and associated behavioural difficulties and psychopathology.
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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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ItemGetting to the heart of teen depression: the relationship between depression and cardiovascular risk in adolescents during wakefulness and sleep( 2013)Depression has been identified as an independent cardiovascular risk factor in adults, where its presence results in higher rates of mortality and adverse cardiac events in patients with and without known cardiovascular disease (CVD). Recent literature suggests preclinical signs of cardiovascular risk are also present in adolescents experiencing depressive symptoms, however little is known about the effects of adolescent clinical depression on cardiovascular health. Moreover, no study has investigated the cardiovascular functioning of clinically depressed individuals during sleep, a state which involves cardiovascular changes including the characteristic decrease or ‘dip’ in blood pressure (BP). The aim of this study was to determine whether clinical depression is associated with an increased risk of cardiovascular disease in otherwise healthy adolescents. Experiment One sought to examine cardiovascular functioning during quiet wakefulness. Participants (n = 889, 352 male) aged 12-18 years were recruited from Victorian secondary schools in the general community. Subsequent to completing mood questionnaires and clinical interviews, 50 eligible participants (25 [6 male] clinically depressed, 25 [6 male] control) took part in a morning cardiovascular assessment at the University of Melbourne. Variables assessed included automatic clinical and continuous beat-to-beat finger arterial BP, heart rate (HR), endothelial functioning, pulse transit time (PTT), as well as cholesterol, glucose and glycohaemoglobin levels. In addition, the cumulative risk of present modifiable risk factors such as smoking was calculated according to the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) risk score, which has been shown to predict coronary calcification in young populations. It was predicted that, compared to controls, depressed adolescents would show evidence of a number of early pathophysiological processes. As hypothesised, between-group analyses revealed depressed adolescents had significantly poorer endothelial functioning, which resulted in decreased vasodilation, and shorter PTT suggesting deterioration in vascular integrity and structure. Depressed adolescents also presented with higher fasting glucose and higher triglyceride levels compared with controls. Furthermore, risk score calculations revealed significantly higher PDAY risk scores in the depressed group indicative of increased engagement in unhealthy behaviours and a higher probability of having advanced atherosclerotic lesions. Contrary to predictions however, no significant differences were found in BP or HR measurements. In order to have a more complete understanding of the cardiovascular health of depressed adolescents, Experiment Two was designed to asses BP and HR during sleep. The BP profile at sleep onset was of particular interest as a blunted decline in BP is associated with target organ damage and increased cardiovascular risk. A subgroup of female participants (8 clinically depressed, 10 control) who completed Experiment One also participated in an overnight cardiovascular assessment. Whole-night polysomnography was conducted with continuous beat-to-beat finger arterial BP and HR monitored via Portapres and ECG, respectively. Data were analysed as an average of the first 6 hours of sleep as well as 2-minute epochs of stable sleep averaged within sleep stages. Further analyses of 30-second epochs were averaged across the pre-sleep wakefulness and the first ≥5 minutes of continuous stable Stage 2 in the sleep onset period. Analyses revealed that although no significant group differences in BP or HR were found during morning wakefulness, depressed adolescents presented with higher systolic, diastolic and mean arterial BP across the whole night and across sleep stages. The difference between groups (~11 mmHg) was found to not only be statistically but also clinically significant. Depressed adolescents also displayed a blunted systolic BP decline at sleep onset compared with controls. This heightened nocturnal BP and blunted decline represent early changes in BP regulation and could be a preclinical marker for depressed adolescents at high risk of cardiovascular disease. A number of plausible mechanisms may explain the heightened BP including a failure to shift to parasympathetic dominance during sleep, increased cortisol levels as a result of a dysregulated hypothalamic-pituitary-adrenocortical axis, and limited vasodilation at night due to endothelial dysfunction as found in Experiment One. Although the mechanisms are still unclear, the results suggest that depression has a significant adverse effect on the cardiovascular system in the early stages of life. Given that risk factors are known to continue to adulthood, the heightened nocturnal BP, increased triglyceride and vascular changes may increase risk for future cardiovascular problems such as hypertension. Identification of those at high-risk and intervention should therefore be actioned as early as adolescence as a way to decrease the prevalence and global burden of CVD.
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ItemBrain network correlates of adolescent self-control( 2013)The ability to engage self-control by overcoming automatic habits and impulses is critical to the progression from adolescence to adulthood, and can predict long-term health outcomes. Research into self-control has involved a number of techniques, with the psychology of individual differences and cognitive neuroscience featuring prominently. Despite their diverse perspectives, these two fields have converged recently to suggest that variations in both cognitive and personality-based measures of self-control rely on a common set of functional interactions within and between two canonical large-scale brain systems: The so-called cognitive control (CCN) and default-mode networks (DMN). However, very little is known about how individual differences in self-control during the teenage years relate to the functional activity and connectivity of these networks. This thesis aimed to fill this gap using a series of functional magnetic resonance imaging (fMRI) experiments designed to assess, in detail, the large-scale functional brain networks that support adolescent self-control as defined using both cognitive and questionnaire-based measures. To achieve this, data from the same sample of participants was used in a series of five experiments that progressed in the focus on large-scale brain networks from simple brain mapping, through individual differences analyses of activity and functional connectivity, and then ending with modularity analyses. During each experiment, a specific interest was also to determine the similarities and differences between the task-related versus the resting-state CCN and DMN to determine how self-control networks are engaged during task performance. The main hypothesis was that the task-related activity and functional connectivity of core regions that comprise the CCN and DMN would be most related to individual differences in cognitive and effortful control. Methods: The participants comprised a healthy sample of adolescents (N=73; mean age (SD) =16.5(0.5); 51% female) from a longitudinal study who completed questionnaire measures of effortful control, a temperamental index of self-control capacity in daily life; an fMRI interference control paradigm (the Multi-Source Interference Task; MSIT); and a resting-state fMRI sequence. Using these data, five experiments were then devised to investigate how the task-related activity, task-related functional connectivity, and resting-state functional connectivity of the CCN and DMN support self-control behaviours as measured by self-reported effortful control (ECc), parent-reported effortful control (ECp), MSIT interference effect, and MSIT accuracy. The experiments were designed to build upon each other to comprehensively address the thesis aim. Chapter 6 established the main measures used throughout the thesis related to the sample, and to the behavioural and brain measures related to self-control. The second experimental chapter (Chapter 7) examined how MSIT-related activation and within each region comprising the CCN and DMN correlated with EC and MSIT performance. Chapter 8 then established the functional connectivity parameters for each participant and employed the graph theoretic measure of node strength to investigate correlations between behaviour and the resting-state and task-related functional connectivity of each region. More specific pair-wise functional connectivity relationships between brain regions were then investigated in Chapter 9 in order to identify functional connectivity sub-networks related to each behavioural variable. Finally, Chapter 10 then integrated the results into a broader functional connectivity picture using a data-driven technique to identify how the putative network nodes aggregated into functionally specialized modules. Results: Contrary to the main hypothesis of this thesis, the results indicated that each behavioural measure was related to a different large-scale brain network, which appeared to be specific to the condition under investigation (i.e., task or rest). For example, the MSIT interference effect was associated with a putative visual attention network during task performance but not at rest; MSIT accuracy was mainly associated with the connectivity of default-mode regions; and effortful control was correlated with complex subnetworks where interactions between the CCN and DMN appeared to be most important. The importance of interactions between networks was then emphasised in the modularity analysis, which showed subtle, but behaviourally important, differences in network modular organization between the task and resting-state conditions. Conclusion: Overall, the results of the thesis supported the idea that competitive and cooperative relationships between the cognitive control and default mode networks support adolescent self-control. However, the experiments highlighted the importance of the engagement of different subnetworks for different measurements of self-control, and functional connectivity differences between rest and task conditions that may predict behaviour. Together, these findings emphasise the importance of considering the flexibility of large-scale networks when considering the neural basis of adolescent self-control, rather than a single canonical brain region or circuit.
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ItemSpeaking for themselves: how do adolescents define their quality of life after a traumatic brain injury?( 2013)Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young people (Yeates et al., 2002). The status of quality of life (QoL) in paediatric TBI is mixed. Our recent meta-analysis of paediatric QoL (Di Battista et al., 2012) found that good QoL outcomes are contingent on milder injuries, proxy reporting and early assessment whereas poor outcomes reflect more severe injuries and later assessment. Available paediatric QoL data is largely based on the health-related quality of life (HRQoL) paradigm; where a good outcome is contingent on what one can accomplish or achieve, as assessed by proxies. Information on the subjective well-being (SWB) component of QoL is limited. When estimating the HRQOL in adolescents, the presence of anxiety and depression and the quality of social relationships are important considerations, because adolescents are entrenched in social development during this phase of maturation. The influence of anxiety, depression and loneliness on HRQOL in adolescent survivors of TBI has not been documented. The goal of this study was to explore the adolescent experience of quality of life, anxiety, depression and loneliness after a traumatic brain injury. This study is a mixed-methods assessment of the impact of mood states and loneliness on quality of life (QoL) in adolescents who have survived a traumatic brain injury (TBI). METHOD: mixed method/cohort pilot study (11 adolescents, mild to severe TBI; 9 parents), using self-report (anxiety, depression, HRQoL, loneliness) and proxy-report measures (anxiety, depression and HRQoL) and clinical psychiatric interviews (adolescent only). The adolescent experience of these states is not accurately reflected by parental proxy. Self-reported depression and age at injury were associated with health-related quality of life outcomes, while anxiety was not. Severity of injury was not related to secondary outcomes. Adolescent narratives revealed that having experienced a TBI does not a priori impact upon perceived QoL. The impact of a TBI on QoL could be positive or negative. Post-injury changes in ability were not always attributed to the injury, but rather to a sense of normal age-related changes as identified by the adolescent. Changes as a result of the injury were not always considered important to the adolescent’s view on QoL. Adolescents identified social and inter-personal discrepancies and the emotional consequences of these discrepancies. Ultimately, the individual’s appraisal of their identity from pre to post injury life related to their current sense of well-being. Friendships were very important considerations for post-injury well-being. Processes of post-traumatic growth were identified in the adolescent narrative. The findings of this study are novel and have important implications for both research study design and clinical care settings involving adolescent survivors of a TBI.