Delusions - Etiology, Frequency & Neural Correlates

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Delusional experiences are a burdensome psychiatric symptomatology leading to great psychological strain and fear. In addition, it oftentimes entails social withdrawal as well as a considerable loss of functioning. Delusions occur in a number of psychiatric diseases including schizophrenia, uni- and bipolar affective disorder or posttraumatic stress disorder. The investigation of the development of psychiatric diseases is impeded by the occurrence of a multitude of differing symptoms and hence, a very heterogeneous phenomenology. Assumably, the elucidation of etiological factors should be alleviated by exploring a more narrowly defined psychopathological variable. Therefore, the project focuses on the most frequent forms of delusional ideation: referential and paranoid ideation. Since both forms are not only observable across disease entities, but are also present in the general population, they will be characterized in a non-clinical sample. This offers the important advantage to investigate them in the absence of confounding factors often present in clinical samples (e.g. medication, psychosocial consequences, comorbidity, substance use). The first subproject aims to explore the frequency and dimensionality of delusions in the German general population for the first time. Using Ecological Momentary Assessment (EMA) data of at least 1.000 subjects will be collected. In the second subproject 124 subproject experiencing varying levels of delusional ideation will be analyzed again by psychological and neuroscientific methods. Employing interview, questionnaire, performance tests as well as (f)MRI measures differentiated biopsychosocial model assumptions of the emergence of delusions will be explored. The focus is on the interaction of various variables (Aberrant Salience attribution, Theory of Mind processing, Jumping to Conclusions bias, Executive functioning) at the psychological as well as the neural level. Neural correlates will be studied using network-based approaches, such as Dynamic Causal Modeling (DCM) and Graph Theory. In addition to the more precise characterization of the etiology of delusions, the findings of the project promise meaningful new impulses for the differentiation of biological and psychological treatment approaches.