Source monitoring in hallucinations; A comparison between schizophrenia spectrum disorders and the auditory Charles Bonnet Syndrome

Abstract

Introduction: Auditory hallucinations are seen in different psychiatric and neurological disorders as well as in healthy people. It is suggested that source monitoring impairments in self recognition and an external attribution bias would lead to hallucinations. In this current study this assumption was examined by comparing participants with and without hallucinations. Furthermore, it was examined whether there is a relation between source monitoring performance and the constructs negative affect and insight into the hallucinations. Methods: In this study two groups of participants with hallucinations were included; 40 subjects with the auditory Charles Bonnet Syndrome (ACBS) and 19 participants diagnosed with schizophrenia spectrum disorders. The third group consisted of 16 healthy control participants without hallucinations. Source monitoring was measured by a source monitoring task. Negative affect was measured by the scores on the Beck Depression Inventory, the Beck anxiety inventory and a composited general negative affect score. Insight into the hallucinations was measured by the newly designed Questionnaire Psychotic Experiences. Groups were compared by MANCOVA and correlation analyzes were conducted in order to examine relations between the different variables. Results: The groups did not differ on source monitoring performance and no impairment in self-recognition nor an external attribution bias was found in any of the three groups. For the schizophrenia spectrum group a correlation between higher scores on the BAI and general negative affect and impaired source monitoring performance was found. For the ACBS group a relation between less insight in hallucinations and impaired source monitoring was found. Conclusion: This study failed to confirm the involvement of impairments in self- recognition and an externalizing bias in hallucinations in participants with schizophrenia spectrum disorders and participants with the ACBS syndrome. Based on the differences between these groups on negative affect and insight in hallucinations and the way these constructs correlate with source monitoring, it is seems that the ACBS and schizophrenia spectrum group reflect different groups. Therefore it is possible that for these groups different mechanisms lead to the experience of the hallucinations.