| Summary: | There is an increasing awareness of the limitations of Cognitive Behavioural Therapy for psychosis (CBTp) and researchers are attempting to advance its efficacy. The first part of this thesis was a systematic review of the new CBT approaches for positive symptoms. The evidence for their efficacy was summarised and then examined from a methodological perspective. A search of the literature since 2003 produced sixteen studies, falling into two main strands: an interventionist causal model approach, with studies indicating the potential for greater effect sizes for both persecutory delusions and auditory hallucinations; and 'third wave' CBT, with mindfulness and acceptance-based approaches demonstrating limited benefits for auditory hallucinations. The new developments are potentially a step forward from standard CBTp and implications for future research are discussed. Multiple factors have been identified in the development of persecutory thinking. The second part of this thesis specifically focused on interpersonal sensitivity as a hypothesised causal factor of persecutory delusions, in line with the interventionist causal model approach referred to above. The study evaluated the impact of a newly-devised cognitive behavioural intervention for interpersonal sensitivity (CBT-IPS) for patients with persecutory delusions. The therapy was tested in an uncontrolled pilot study, which included a 2-week baseline period and I-month follow-up. CBT-IPS did not depend on disputing the validity of delusional beliefs• but on reducing concerns regarding criticism or rejection. Eleven participants with persecutory delusions and a psychosis diagnosis completed the 6-session CBT-IPS intervention. Results indicated statistically significant reductions with large effect sizes for both interpersonal sensitivity and persecutory delusions, consistent with the hypothesised causal role. Participants also reported a significant decline in negative beliefs about others. All gains were maintained at follow-up. This was the first test of CBT-IPS and it shows promise as a therapeutic intervention. The next step is to conduct a randomised controlled trial.
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