This thesis consists of a literature review and a research study exploring the experiences and processes within psychological interventions for people with bipolar disorders. A thematic synthesis was conducted to explore individual experiences of psychological-based interventions for bipolar disorder. A critical appraisal tool was used to assess the quality of the identified studies. The themes identified from the synthesis were compared with existing literature around individual experiences of bipolar disorder. The review highlighted methodological limitations of the studies and suggested areas for future research and clinical implications. The empirical study was based on an existing dataset from the feasibility trial of Think Effectively About Mood Swings (TEAMS), which is a novel cognitivebehavioural approach for people with bipolar disorders. The overall aim of this mixedmethods study was to investigate patterns of change and in-session client-therapist behaviours, in order to improve TEAMS delivery for the next phase of development. Study 1 aimed to examine patterns of change, and in particular, whether sudden gains were present in TEAMS. Study 2 explored potential factors influencing therapeutic change, such as client involvement and therapist responsiveness, through an in-depth analysis of recorded therapy sessions. Template analysis was used to explore session transcripts of clients who had improved following TEAMS, compared to those who made no change. The findings from Study 1 showed there were minimal sudden gains found within the TEAMS therapy. Study 2 found that client involvement was a key factor in the differences between the two groups. Further research into the experiences and processes of psychological interventions for people with bipolar disorders is needed.