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Abstract
Psychological treatments play a central role in managing bipolar disorder, yet long-term outcomes continue to be poor. Psychological models of the condition are still in their infancy, impeding the development of model-driven therapies and knowledge of how to increase the efficacy of available treatments. Further progress depends on the development of models that encapsulate the complexity of the condition. Psychological research and treatments have focused on bipolar I disorder and extrapolated results to bipolar II disorder despite little being known about this sub-type. This thesis sought to address this gap by undertaking a systematic investigation of psychological processes in bipolar I and II disorder. Prominent psychological models of bipolar disorder were examined and contrasted between the bipolar sub-types.
Study aims were to determine whether bipolar I and II disorder would exhibit differential cognitive style, coping styles and Behavioural Activation Sensitivity (BAS) profiles, and whether relationships between these processes and symptom expression would differ between the bipolar sub-types. Study 1 employed a qualitative methodology to examine a cognitive-behavioural model in bipolar II patients, providing a context from which to approach quantitative investigations exploring differences between the bipolar sub-types. Studies 2 and 3 assessed cognitive style, coping styles and BAS sensitivity in bipolar I and II patients, contrasted with unipolar patients and healthy controls. Studies 4 and 5 prospectively examined the relationship between cognitive style, coping styles, BAS sensitivity and symptom expression in bipolar I and II disorder.
Subtle differences in cognitive style, coping styles and BAS sensitivity - and their relationship with symptom expression - were identified in the bipolar sub-types. Differential features in bipolar I and II disorder suggest that psychological models and treatments need to take into account the nuances of each condition. More sophisticated models integrating cognitive style, coping styles and BAS sensitivity are needed to broaden our understanding of mood regulation difficulties in bipolar disorder. Thesis results will help to inform future psychological models of bipolar disorder and refine psychological interventions for the bipolar sub-types. Overall, this thesis broadens our understanding of bipolar disorder and offers new insights into psychological features of bipolar II disorder.