Background: The current understanding of bipolar disorder attributes a causal role to abnormal psychological processes in its development. However, little research has so far adequately tested this assumption. Two approaches might be employed to do so: (i) longitudinal investigations of psychological processes in patients (with some limita-tions); (ii) examinations of such processes in high-risk individuals. Methods: Three cohorts of participants were examined: two different cohorts of adults with bipolar disorder (using secondary data, Chapter 2 and 3), and adolescent offspring of parents with bipolar disorder, in comparison to offspring of control parents (Chapters 4, 5, 6). In adults with bipolar disorder, the associations between self-referential proc-esses and symptoms of depression and mania (Chapter 2), and the inter-relationship be-tween self-esteem, mood and response styles (Chapter 3) were examined longitudinally. In adolescent children, longitudinal relationship between mood, self-esteem and coping style (Chapter 4), abnormal psychological processes (Chapter 5), and explicit and im-plicit self-esteem and their discrepancies (Chapter 6), were investigated. Results: In adults with bipolar disorder, symptoms of depression and mania were asso-ciated with distinct psychological processes, with self-esteem being the most robust predictor (Chapter 2). However, mood, rather than self-esteem, instigated, and was af-fected by, an engagement in coping strategies (Chapter 3). In adolescents, index adoles-cents showed compromised capacity to employ adaptive coping, and employed risk-taking in response to low self-esteem (Chapter 4). Further, no differences in abnormal psychological processes were found, unless children have already met diagnostic crite-ria for psychiatric disorders (Chapter 5). Despite no differences in explicit and implicit self-esteem, index offspring reported marginally higher level of self-esteem discrepan-cies. In addition, damaged self-esteem (i.e. low explicit self-esteem and high implicit self-esteem) was related to symptoms of depression, whilst low implicit self-esteem to symptoms of mania. Conclusions: Early coping abnormalities are important markers of individuals at ultra high risk of bipolar disorder. Further, the relevance of self-esteem in bipolar disorder has been suggested. Implications for future research and psychotherapy are discussed.