This thesis investigates the effectiveness of self-management interventions for people with severe mental illness. Part one is a systematic review and meta-analysis of self-management interventions for those with severe mental illness. Part two reports on resilience outcomes in a randomised controlled trial of a peer-delivered self-management program for people recently discharged from crisis care (ISRCTN registration: http://www.isrctn.com/ISRCTN01027104). It also investigates baseline predictors of resilience. Part three, the critical appraisal, examines the concepts of self-management and resilience. It also considers the methodological and conceptual challenges of conducting randomised controlled trials of complex mental health interventions, particularly in populations where outcomes are largely socially determined.