Cognitive factors maintaining persecutory delusions in psychosis
: the contribution of depression

Student thesis: Doctoral ThesisDoctor of Philosophy


Persecutory delusions are one of the most common and distressing symptoms of psychosis. Many studies indicate an association of persecutory delusions with depression. A direct role for depression-related cognitive factors in the maintenance of persecutory delusions has not been systematically examined, despite such processes being implicated in a cognitive model. To determine whether depression in people with persecutory delusions is associated with the same cognitive factors implicated in major depressive disorder, and to examine these factors as predictors of the persistence of persecutory delusions over time. A systematic literature review formed the basis of two linked studies: one cross-sectional and one longitudinal. In the first study, 60 participants with persecutory delusions and schizophrenia spectrum diagnoses were classified into two groups, according to whether or not they met ICD-10 criteria for major depression. Assessments were made of delusions, depression and key cognitive factors from the literature: schematic beliefs, avoidance, rumination, memory specificity and problem solving. The groups’ scores were compared, and the same comparisons were made between 30 participants with non-psychotic depression and 30 non-clinical controls. For the second study, 54 participants with delusions were re¬assessed six months later, and predictors of symptom persistence were examined. 50% of participants with persecutory delusions met diagnostic criteria for major depression. With baseline paranoia levels controlled, higher baseline depression predicted higher paranoia six months later. Negative schematic beliefs about the self and problem solving deficits predicted the persistence of both paranoia and depression over time. Coexisting depression predicts the persistence of persecutory delusions, suggesting a causal association.
Trials are warranted of depression-related therapeutic techniques for people with delusions, including those that target negative schematic beliefs about the self. An improved understanding of the mechanisms that maintain paranoid beliefs can enable the development of better treatments.
Date of Award2012
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorPhilippa Garety (Supervisor) & Daniel Freeman (Supervisor)

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