Centre for Youth Mental Health - Theses
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ItemAntecedents of incident bipolar disorder in youth( 2017)Background: Bipolar disorder (BD) is a serious mental illness characterised by episodes of mania and depression. The disability associated with this disorder and the observation that at least a sub-proportion have a progressive course suggests that early or preventive interventions may be an effective strategy to minimise the disability. However, prevention efforts for BD require characterisation of targets for such interventions. Aims and objectives: Thus, the overall aim of this research program was to describe the pre-onset illness stages related to the development of incident (hypo)manic episodes and their associated functional impairment. Specifically, we aimed to examine clinical populations where preventive efforts may be more feasible. The objectives included identification of i) baseline characteristics associated with later BD among non-bipolar help-seeking youth; ii) rates and predictors of transition from major depressive disorder (MDD) to BD in previously published studies; iii) instruments that have prospective predictive validity in identifying BD and iv) the precursors of functional impairment in the post-illness period. Methods: This thesis comprises five studies that have examined these issues using diverse methodologies – using systematic review, meta-analyses and longitudinal cohort designs. Three studies involved examining baseline characteristics associated with the development of later BD from non-bipolar states. One study identified the instruments that have been used to predict the later onset of BD using a systematic review, while the final study examined the pre-onset predictors of later functioning among young people with first episode BD. Main results: The characteristics associated with later BD in the two cohort studies included subthreshold manic symptoms, comorbid substance use, severity of depression, antidepressant use and lower functioning. Meta-analyses identified that family history of BD, comorbid psychotic symptoms and lower age of onset of depression was predictive of transition from MDD to BD. The systematic review identified few instruments with prospective validity for predicting BD onset that had been replicated in clinical cohorts. However, instruments with validity in non-clinical cohorts, or those without replication were described. Across the first four studies, combinations of risk factors were associated with a greater risk of transition to BD. Poor premorbid adjustment in the pre-onset phase was predictive of later functioning among youth with first episode mania. Discussion: The findings of these studies point to the need to use combinations of risk factors identified using validated instruments, particularly in young people to predict the onset of BD. This may then help develop preventive interventions that may be tested in studies that are feasible and have adequate statistical power. Incorporating functional precursors into pre-illness stages may help with prevention of functional impairments. A putative instrument which may decrease measurement bias is also proposed. The primary limitation of the included studies was in the post-hoc nature of analyses and the associated lack of availability of all possible baseline confounders. Additionally, low statistical power limited the ability to examine certain associations. Future studies should examine multiple confounding variables in longitudinal cohorts of youth and young adults. Larger cohorts that are enriched for multiple risk factors may help improve statistical power.
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ItemPromotion of self-help strategies for sub-threshold depression: an e-mental health randomised controlled trial( 2012)Background: Sub-threshold depression refers to clinically relevant depressive symptoms that fall short of a diagnosis of major depression. Sub-threshold depression is very common in the general population, impairs functioning, increases the risk of developing major depression, and poses a significant burden at the population level. Public promotion of greater use of effective self-help strategies for depression has been proposed as one technique to reduce this population burden. Improving self-help strategies could reduce symptoms of sub-threshold depression and prevent major depression. Depression experts have identified several self-help strategies that are helpful for sub-threshold depression. The aim of the study was to develop messages based on these strategies that could be promoted to members of the public with sub-threshold depression, and to test whether their promotion was effective. Method: Twelve email messages (‘Mood Memos’) were developed, based on self-help strategies endorsed as effective and feasible by depression experts. The email messages were developed with reference to theories of behaviour change, persuasion, and health communication, in order to persuade recipients to engage in the self-help behaviours. The effectiveness of these emails was evaluated in a randomised controlled trial. Recruitment was via internet-based sources and participants joined the study by visiting the website www.moodmemos.com. Adults aged 18+ with sub-threshold depression who were not receiving professional treatment for depression were eligible to participate. Participants were randomly allocated to receive emails twice weekly for six weeks in a fully automated intervention. The active group received emails based on the effective self-help strategies and the control group received emails containing general information about depressive disorders. Assessment points were at baseline, midway through the intervention and at the end of the intervention (6 weeks post-baseline). The primary outcome was depression symptom score on the Patient Health Questionnaire-9 (PHQ-9). Secondary outcomes were psychological distress, assessed with the ten-item Kessler Psychological Distress Scale (K10), and level of functioning, assessed with the Work and Social Adjustment Scale. The primary hypotheses were that the emails containing self-help strategies would reduce depression symptoms and reduce the incidence of major depression more than the control emails post-intervention. Results: The study recruited an international sample of 1,326 adults with sub-threshold depression. There was a small, significant difference in depression symptoms post-intervention, favouring the active group (Cohen’s d = 0.17, 95% CI: 0.01 to 0.34). There was also a higher, though non-significant, risk of major depression in the control group (Relative Risk = 1.32, 95% CI: 0.89 to 1.98). A similar effect was found for psychological distress (d = 0.22, 95% CI: 0.05 to 0.38), but effects on functioning were less strong, with no significant difference between the active and control groups (d = 0.12, 95% CI: -0.05 to 0.28). A mediation analysis indicated that the effect of the emails on depression symptoms was completely mediated by the use of the self-help strategies promoted in the emails. Discussion: Overall, the results indicate that promoting effective self-help strategies to the public via automated emails was effective for sub-threshold depression. The improvement in depression was associated with use of the self-help strategies promoted in the emails. The delivery of self-help messages via email is a scalable, easily disseminated intervention. The study is a novel contribution with potential to reduce the large population burden of depression.