Different psychopathological courses between chronic interictal psychosis and schizophrenia

Objective: The clinical course of interictal psychosis (IIP) has not yet been investigated. We aimed to compared the psychopathology and time-relevant indices between chronic IIP (CIIP) and schizophrenia (SC) Methods: In this comprehensive psychopathological study, patients with chronic psychosis with and without epilepsy (127 with CIIP and 187 with SC) were compared. Psychopathology was measured using the Brief Psychiatric Rating Scale (BPRS): total, negative symptoms (NSs), positive symptoms (PSs), and anxietydepressive symptoms (ADSs). Time-relevant indices included age at the time of evaluation, age at the onset of psychosis, and duration of psychosis. The psychopathology of psychosis types and time-relevant indices were analyzed using Pearson's correlation coefficient analysis of covariance. Results: Age at the time of evaluation was significantly correlated with NS, and ADS scores. Age-relevant trajectories significantly interacted with psychosis types. As age advanced, patients with SC exhibited increased scores, whereas patients with CIIP often exhibited decreased (or unchanged) scores. Age at onset of psychosis was significantly correlated with NS and ADS outcomes in patients with CIIP, whereas it was not correlated in patients with SC. There were significant interactions between age at onset and psychosis types. Patients with early-onset CIIP exhibited higher NS and lower ADS scores, whereas patients with SC exhibited no particular trajectory. The duration of psychosis significantly interacted with the psychosis types in the BPRS total, NSs and PSs. As duration increased, patients with CIIP exhibited no significant relationship, whereas patients with SC exhibited significantly higher psychotic scores. Conclusion: Psychopathological courses differ between patients with CIIP and SC. Although patients with SC often exhibit deteriorations in psychotic symptoms, patients with CIIP exhibit no distinct deterioration. These findings can contribute psychiatric nosology, treatment strategies, and prediction outcomes.