This thesis addresses risk factors and proposed mechanisms to explain relapse to depression. Volume 1 comprises three parts: Part 1 is a literature review consisting of meta-reviews of systematic and non-systematic reviews of studies reporting on risk factors for relapse to depression, and a systematic-review of neuroimaging and experimental studies investigating risk factors for relapse and potential mechanisms of action of these risk factors. The reviews found that only residual symptoms of depression at the end of treatment and childhood maltreatment were sufficiently evidenced as predictors of relapse and neither have great clinical utility. A number of psychological and neuropsychological factors were suggested to play a role in conferring risk for relapse. Considering the inter-relationships between these factors the reviews were used to propose a conceptual framework which may be used to help guide future research into relapse to depression in adults. Part 2 is an empirical paper in which data were analysed from service users of a primary care mental health service to identify risk factors for relapse and for the presence of residual symptoms, and survival analysis methods were used to determine when relapses occur most often and what factors impact survival. In addition, a prospective cohort study was formed to investigate the relationship between cognitive control and depressive symptoms. The findings confirmed that cognitive control can be used to predict residual symptoms of depression post-treatment and therefore potentially to predict relapse. Part 3 is a critical appraisal focussing on the theoretical reasons as to why studying relapse in a manner as used in the prospective study is so important and discusses the logistical difficulties conducting such research in the current context of NHS services and of the D.Clin.Psy research project. Methodological decisions made that impacted upon the research process are discussed and reflective conclusions are offered
