Biased interpretation in paranoia and paranoid psychosis

There is now considerable evidence showing pathology congruent cognitive biases in the interpretation of emotionally ambiguous information. Such biases selectively prioritise the processing of information that can confirm a pathological belief and thereby play a direct role in maintaining associated pathology. Although interpretation biases are well documented in the affective disorders, little work has been done in other psychopathologies, including psychosis. This thesis reports five studies investigating the degree to which pathology congruent interpretation biases are present in paranoia and paranoid psychosis. Chapter 1 introduces the literature on biased cognition in paranoia and paranoid psychosis. Chapter 2 (Experiment 1, n = 70) provides an evidence base for the interpretation biases relevant to paranoid thinking and identifies their level of content specificity in the non-clinical population. Chapter 3 (Experiment 2, n = 70) investigates the hierarchy and severity of paranoid thinking in the non-clinical population. Chapter 4 (Experiment 3, n = 90) validates the most sensitive measures of interpretation and reasoning biases in a clinical sample characterised by paranoid and non-paranoid psychosis. Chapter 5 (Experiment 4, n = 138) tests the prediction of interpretation biases on paranoid thinking and anomalous perceptions. Chapter 6 (Experiment 5, n = 60) tests the effectiveness of a novel ‘Cognitive Bias Modification’ for psychosis programme for use in the reduction of paranoid interpretations. Chapter 7 discusses findings in the context of the wider literature and in relation to existing cognitive models of psychosis. Results from this thesis demonstrate evidence that paranoid and valenced interpretation biases are associated with higher levels of trait paranoia. Individuals with higher levels of trait paranoia are also shown to make less non-paranoid interpretations of emotionally ambiguous information than individuals with lower levels of trait paranoia. Interpretation is an underlying cognitive process that, when biased in a paranoid direction, has the potential to contribute toward maintaining a paranoid psychotic state. Personal Contribution to the Investigation As part of the investigation of this thesis, I developed the paranoia set materials for the following tasks of interpretation bias: the Similarity Ratings task, the Scrambled Sentences task, the Relatedness Judgement task and the Emotional Jumping to Conclusions task used in Experiment 1, Experiment 3 and Experiment 5. I also developed the valenced set materials for the Relatedness Judgement task used in Experiment 1 and Experiment 3 and adapted the Emotion Identification task used in Experiment 1, Experiment 2 and Experiment 3 with my colleague JongSun Lee. Tasks of paranoid interpretation bias used in Experiment 2 were developed with the assistance of former MSc students Emily Leathers-Smith and Sara Assadi. The ‘Cognitive Bias Modification’ for psychosis programme and the Achievement and Relationships Attribution task (version 2) were developed with the assistance of former MSc students Annabel Edwards and Husniye Guven. I collected data for Experiment 1, Experiment 3 and Experiment 4. Emily Leathers-Smith and Sara Assadi assisted with data collection for Experiment 2 and Annabel Edwards and Husniye Guven assisted with data collection for Experiment 5. I served as the ‘stooge’ for the Stooge-Laughter task used in Experiment 5. Data sets from each experiment were analysed independently. I would like to acknowledge the above individuals for their hard work and dedication to assist with the development of materials and recruitment of participants. You were each a pleasure to work with and your contributions were integral to the success of this thesis.