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Persecutory delusions are a prevalent symptom in psychotic disorders. In addition to attribution and reasoning biases, psychological models emphasize the relevance of low self-esteem for the formation of persecutory delusions (Freeman et al., 2002). Also, a number of studies speak for the notion that patients with persecutory delusions suffer from feelings of inferiority (Freeman, 2007). As a consequence, cognitive-behavioral therapy programs for patients with schizophrenia include interventions that aim at improving self-esteem (Fowler et al., 1995; Moritz, Vitzthum, et al., 2010).
However, the specific role of self-esteem in the formation and maintenance of persecutory delusions is not clarified yet. In particular, there are still outstanding questions concerning the levels of explicit and implicit self-esteem in patients with persecutory delusions and concerning the role of fluctuations in self-esteem in the formation of paranoid beliefs. Therefore, the aim of the present dissertation project is to investigate these aspects of self-esteem in persons with persecutory delusions. A deeper understanding of the complex relation between self-esteem and persecutory delusions could be helpful in developing specific psychological interventions for patients with delusions.
Paper 1 demonstrated that patients with acute and remitted persecutory delusions have low levels of explicit self-esteem compared to healthy individuals. However, there were no group differences in levels of implicit self-esteem. Also, there were no differences between levels of explicit and implicit self-esteem within the patient sample.
Paper 2 provided information about the role of self-esteem in the formation of paranoid beliefs. In a nonclinical sample, social stress led to an increase of paranoid ideation in individuals with high vulnerability. This process was further mediated by a reduction in self-esteem.
The study of paper 3 investigated the relevance of self-esteem and self-schema to persecutory delusions by reviewing the existing research in this field. There was sufficient evidence that persons with clinically relevant or subclinical persecutory beliefs are characterized by low global self-esteem and negative self-schemas. In addition, there was consistent evidence from a small number of studies that patients who believe that their persecution is deserved have low self-esteem and that self-esteem is instable in patients with persecutory delusions.
Overall, the findings of the present dissertation project indicate that low global explicit self-esteem, negative self-schemas and an acute reduction in self-esteem are relevant factors for the formation and maintenance of persecutory beliefs. These results are integrated into an explanatory model, which describes the role of self-esteem in the formation of persecutory delusions and considers previous adverse experiences as a potential cause of impaired self-esteem. Finally, the findings of the present dissertation project stress the need for specific interventions that aim at improving and stabilizing the patients´ self-esteem.