Optimising Sleep-Wake And Circadian Rhythm Interventions For Youth With Mood Disorders

Mood disorders are ranked as the most burdensome disorders for youth worldwide. The consequences for this age group are serious, including exacerbated symptoms, persistent syndromes, and suicide. A treatment target of interest is sleep-wake and circadian rhythm disturbances, as disruptions in these phenomena trigger and prolong mood symptoms. However, efficacious sleep-wake and circadian rhythm interventions for youth with mood disorders are limited, potentially owing to a lack of youth-specific programs and inadequate assessment of sleep-wake and circadian rhythms as outcome measures. A second treatment target of interest is maladaptive rumination. Maladaptive rumination has been shown to predict depression onset, maintenance, and relapse in youth with mood disorders. Importantly, rumination shares bidirectional links with sleep-wake disturbance in youth. However, the commonalities between these phenomena remain unclear, where shared dimensions may represent valuable intervention targets that could optimise future sleep-wake and circadian rhythm interventions for youth. This thesis aimed to address these potentially significant gaps through a series of empirical and review studies examining sleep-wake and circadian rhythm disturbance, rumination, and the treatment of youth with mood disorders. Within this thesis, five empirical and review studies were conducted: 1) a review of non-pharmacological and psychological interventions targeting sleep-wake and circadian rhythm disturbance in youth with mood disorders; 2) a cross-sectional analysis of circadian rhythm disturbances in youth with mood disorders; 3) a pilot of a novel youth-specific sleep-wake and circadian rhythm intervention for youth with mood disorders; 4) a review of rumination as a key biomarker for mental disorders in youth and as a modifiable treatment target; and 5) a longitudinal examination of common dimensions between sleep-wake disturbance and rumination as trans-diagnostic predictors of illness trajectories in at-risk youth. These findings provide the foundation for an optimised sleep-wake and circadian intervention for youth with mood disorders, and bring to light the necessary dual inclusion of rumination and sleep-wake and circadian rhythms as intervention targets for this patient population