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Abstract
The high prevalence of anxiety disorder (ADs) in those with bipolar disorder (BD) and the adverse impact of this comorbidity on outcome have been well documented in the literature. However, the mechanisms that underpin this comorbidity are yet to be adequately explored. Recent transdiagnostic theories of BD propose that common underlying mechanisms give rise to, and maintain, both anxiety and BD symptoms. This thesis explores those transdiagnostic psychological mechanisms in order to contribute to a plausible psychological account of the high comorbidity between these conditions.
A series of four studies were conducted across four samples: two clinical samples, a BD pedigree family sample and a sample deemed to be “at-risk” of developing BD. These four studies explored cognitive and emotion regulation strategies, already shown to be characteristic of BD and the ADs, as potential mediating mechanisms of the co-occurrence of their shared symptoms. There are several key findings of this thesis: 1) overall, BD patients with anxiety symptoms/ADs showed more dysfunctional cognitive and emotion regulation styles compared to those with BD only; 2) perfectionism was the only significant mediator that may underpin the relationship between BD and anxiety symptoms/ADs, and this may be most relevant for comorbid BD and social anxiety disorder compared to the other ADs; 3) stress and anxiety symptoms are elevated in those with BD/AD and warrant treatment; 4) extreme positive and negative appraisals of activated states, a cognitive style specific to BD, were elevated in those deemed to be “at-risk” of developing BD who also had a comorbid anxiety disorder, pointing to an important potential mechanism, however, studies with large numbers area required.
It is concluded that more targeted psychological treatment for comorbid BD and ADs/anxiety symptoms are required to ameliorate the increased morbidity and mortality associated with both conditions. To this end, this thesis presents targets for future research and the development of more effective treatments for this common comorbidity.