Longitudinal Factor Structure of the Brief Psychiatric Rating Scale among Incident Cases of Schizophrenia Attending a Nigerian Hospital

Abstract

Background: Schizophrenia, from its early conceptualization, has been described in distinct clinical subtypes. However, these categories were found not to be stable phenotypes over time, hence the dimensional option, whereas at cross‑sectional level, the dimensions of psychopathology have been replicated across studies; there is dearth of data on the longitudinal stability of the factor structure of the symptoms of schizophrenia in African populations. Aim: This study examined the longitudinal stability of the factor structure of the 18‑item Brief Psychiatric Rating Scale (BPRS) across intervals of 16‑week naturalistic treatment follow‑up. Patients and Methods: Consecutive incident cases that fulfilled the criteria for schizophrenia were recruited into the study. After a baseline assessment, 160 incident cases of schizophrenia were followed up 4 weekly for indicators of symptomatic outcome for 16 weeks. The Brief Psychiatric Rating Scale (BPRS) assessments were conducted in clinical interviews and with the Scale for Assessment of Negative Symptoms (SANS). Five BPRS assessments were made across the monthly intervals of follow‑up. Exploratory factor analyses (EFA) using maximum likelihood extraction and varimax rotation with Kaiser normalization was used to extract the factors. Results: A four‑factor structure was found at baseline, namely negative, positive, depressive/anxiety, and manic symptom dimensions. From week 4, the manic and anxiety/depression dimensions remained invariant over time, while negative and positive symptoms merged into a psychosis dimension that was invariant. Conclusion: The persistence of the mood dimensions supports the DSM‑5 recommendation to include these dimensions in the assessment of schizophrenia psychopathology. The longitudinal emergence and invariance of the psychosis factor echo the idea of unitary psychosis and, along with the prominence of mood dimensions over time, reflect recent molecular genetic findings about the sharing of genes by schizophrenia and mood disorders.