Characteristics and clinical correlates of dimensions of delusional experience in schizophrenia and delusional disorder

Abstract

This study aimed at examining the clinical correlates of dimensions of delusional experience in schizophrenia and delusional disorder. One-hundred and forty six subjects with schizophrenia and the same number of subjects with delusional disorder were assessed for dimensions of delusional experience including conviction, extension, bizarreness, disorganization and pressure, and for a number of clinical variables including familial liability to psychotic and mood disorders, illness characteristics, index episode symptoms, response to treatment and one-year psychosocial functioning. The associations between delusional dimensions and clinical variables were examined in each diagnostic group by means of linear regression analyses. Compared with subjects with delusional disorder, those with schizophrenia displayed higher levels of disorganization and bizarreness and lower levels of conviction, extension and pressure. Dimensions of delusional experience showed a rather different pattern of associations with clinical features both within and between diagnoses, with much more significant associations in schizophrenia than delusional disorder. Unlike schizophrenia in that dimensions of delusional experience showed a variety of associations with clinical features, most of the associations in delusional disorder were confined to the dimensions of extension and bizarreness. In schizophrenia, disorganization was the most central characteristic of delusions in that it showed associations with at least one validator within each clinical domain; furthermore all delusional dimensions but bizarreness impacted on some measure of psychosocial functioning. These findings point out the very complexity of delusions and their multidimensional character along with their distinct clinical correlates in schizophrenia and delusional disorder.