| Résumé: | <p>Sleep and depression appear to be closely related, however, the mechanisms involved in the association are not well understood. This thesis focuses on the most commonly presenting sleep complaint, insomnia disorder, and examines emotional processing and emotion regulation as potentially important explanatory mechanisms linking insomnia and depression.</p>
<p>Chapter one introduces emotional processing and regulation as the putative pathways linking depression and insomnia.</p>
<p>Chapter two describes an overnight experimental study investigating possible emotional impairments in individuals with insomnia compared with good sleepers. Findings suggest that overnight memory consolidation and emotional reactivity for negative stimuli are not affected in insomnia. However, autobiographical memory may be biased in insomnia, such that fewer good day’s events were recalled.</p>
<p>Chapter three systematically reviews and evaluates the literature on the extent to which single-component sleep restriction therapy (SRT), an evidence-based behavioural intervention for insomnia, improves depressive symptoms. Findings reveal that SRT was associated with significant small-to-medium effects for reduction of depressive symptoms at post-treatment and follow-up.</p>
<p>Chapter four comprises a secondary data analysis from a randomised controlled trial (RCT) of cognitive behavioural therapy for insomnia (CBT-I) on the effect of emotional processing and regulation. Findings show that CBT-I improved emotional regulation difficulties and increased vigilance to fearful faces relative to neutral faces. No group differences were found on other objective emotional processing tasks, or on measures of worry and rumination.</p>
<p>Chapter five reports on an RCT which was specifically designed to assess the causal mechanisms through which insomnia treatment improves depression. Findings suggest that CBT-I did not engender change in emotion processing bias, despite large improvements in insomnia and depressive symptoms, positive and negative affect, worry, perseverative thinking and emotional regulation. Conversely, early treatment-related changes in negative affect, emotion regulation, and worry were predictors of lagged depression outcomes, and so may be important explanatory factors in the antidepressant effects of CBT for insomnia.</p>
<p>Finally, chapter six reflects on the findings from previous chapters and discusses methodological considerations and future directions.</p>
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