Delusion is one of the most characteristic features of all psychotic disorders. It is an essential symptom for both paranoid schizophrenia and persistent delusional disorder. Although delusion in schizophrenia is described as unorganized and organized in persistent delusional disorder, the delusional themes within these psychosis are relatively similar, with the exception of bizarre delusion which is considered as belonging to schizophrenia.

Identifying the types of delusions in long-term evolution of patients with paranoid schizophrenia and persistent delusional disorder and comparing the frequency of their occurrence in the two groups.

Highlighting significant differences in the frequency of delusional themes in long-term evolution of the two groups of subjects with the diagnosis we mentioned above.

We formed a sample of 60 subjects with persistent delusional disorder and a sample of 34 subjects with paranoid schizophrenia. Patients from both groups had an average course of illness of 10 years. We have quantified for each patient the number of hospital admissions during which they tested positive for a certain type of delusion.

Within the persistent delusional disorder group the most frequent type of delusion was of persecution, followed by delusions of reference. Delusions of persecution and delusions of being followed found to be the most common delusional themes in the paranoid schizophrenia group.

We have not found significant differences between the two groups regarding the type of delusions, with the exception of bizarre delusions. The paranoid theme is the most common theme for both types of pathologies.