The aim of this thesis was to explore the relationship between anger and aggression, insecure attachment, paranoia and social cognition in psychosis. It is presented as three separate papers: 1) a systematic review examining the relationship between paranoia and aggression in schizophrenia spectrum disorders, 2) an empirical study investigating predictors and mediators of trait anger across the psychosis continuum: the role of insecure attachment, paranoia and social cognition and 3) a critical reflection of the research process.Paper one provides a systematic review of the relationship between paranoia and aggression in schizophrenia spectrum disorders. A comprehensive search of the published literature identified fifteen eligible studies. The quality of the included articles is critically appraised during the synthesis of the findings. Methodological limitations, clinical implications and recommendations for future research are considered.Paper two provides an examination of predictors and mediators of trait anger across the psychosis continuum, considering the role of insecure attachment, paranoia and social cognition. Tests of theory of mind and measures of attachment, hostile attribution bias, paranoia and anger were administered to 174 participants (14 ultra-high risk of psychosis, 20 first-episode psychosis, 20 established psychosis and 120 non-clinical). Multiple regression analysis found attachment avoidance, paranoia and hostile attribution bias were significantly related to trait anger. Mediation analysis revealed paranoia mediated the relationship between attachment avoidance and trait anger. The results are discussed with consideration to previous research and limitations of the study. Clinical implications and recommendations for future research are also offered.Paper three provides a critical reflection of papers one and two, with reference to their design, implementation and interpretation. Personal reflections of the research process as a whole are also provided.