What do bizarre delusions mean in schizophrenia?

Background: Bizarre delusions are a hallmark of schizophrenia. The symptom “Unusual Thought Content” (G9) of the Positive and Negative Syndrome Scale (Kay, S.R., Flszbein, A., & Opfer, L.A. (1987). The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophrenia Bulletin, 13, 261–276.) is defined as “thinking characterized by strange, fantastic, or bizarre ideas, ranging from those which are remote or atypical to those which are distorted, illogical and patently absurd”. The aim of the present study was to investigate the relationship between symptom severity as assessed by PANSS component G9 and the delusional content communicated by the patient. Methods: We compared the G9 PANSS scores between patients with 2, 3, 4, and 5 types of delusions. After that, clinical and demographic variables were compared between patients with G9 ≤ 4 (absent to moderate severity score) and patients with G9 ≥ 5 (severe to extreme severity score). Result: Patients with more types of delusions tended to have higher G9 mean scores. Patients at first episode of psychosis (P = 0.033), and with early response to antipsychotic (P = 0.001) tended to present lower G9 scores. Conclusions: This finding suggests that the clinical notion of “bizarreness” is more associated with a chaotic diversity of delusional themes out of context than with a single systematized delusional core.