The focus of this thesis is on paranoia and the factors that are thought to influence its development and maintenance. This thesis consists of three parts. Part one presents a systematic literature review on the evidence for a hostile attribution bias in paranoia. No systematic review has yet considered the extent to which this social cognitive bias is associated with paranoia. The evidence for this relationship is considered in the context of both clinical and non-clinical populations. The results supported hostility bias as being significantly associated with the specific experience of paranoia, rather than the broad diagnosis of psychosis. Part two is an empirical paper on attachment style as a predictor of paranoia in a non-clinical population. The results supported the relationship between paranoia and hostility bias, as expected, but in the context of attachment style this relationship was no longer significant. As per our hypotheses, attachment anxiety and attachment avoidance were both highly significant predictors of paranoia, suggesting that hostility bias was an expression of attachment style. Findings are discussed in relation to the evidence base, new directions for future research and clinical practice recommendations. Part three is a critical appraisal discussing conceptual issues, development of the methodology and reflections on the research proces
