Diagnostic Stability of First-Episode Psychotic Disorders and Persistence of Comorbid Psychiatric Disorders Over 1 Year

Objective: Diagnostic stability is an important indicator of the reliability and validity of psychiatric diagnoses and has implications in clinical practice and research. While several studies have investigated the diagnostic stability of first-episode psychosis (FEP) disorders, less is known about psychiatric comorbidity in FEP and the persistence of such comorbid conditions over time. Our study aimed to confirm the diagnostic stability of FEP disorders and determine the variation in persistence of comorbid substance use disorders (SUDs), mood disorders, and anxiety disorders over 1 year. Method: The Structured Clinical Interview for DSM-IV-TR Axis I Disorders-Patient Edition was conducted at first presentation and repeated after 1 year (or reconstructed) for 214 FEP patients at the Prevention and Early Intervention Program for Psychoses-Montreal. Results: Psychotic disorder diagnoses were retained by 76.2% of patients at 1 year, schizophrenia being the most stable diagnosis (92.1%). Most diagnostic shifts were to schizophrenia and schizophrenia spectrum disorders. Comorbid SUDs, anxiety disorders, and mood disorders persisted for 50.7%, 64.0%, and 16.7% of patients, respectively. Many new cases of each of these disorders also emerged at 1-year follow-up. Conclusions: These findings demonstrate the stability of primary psychotic disorder diagnoses and greater fluidity of comorbid psychiatric diagnoses, with anxiety disorders persisting as comorbid conditions more than mood disorders and SUDs. These results highlight the importance of repeating a structured diagnostic assessment longitudinally, especially for consideration of comorbid conditions.