Diagnostic stability of functional psychosis: A systematic review

Abstract

Objective: Stability of diagnosis is one measure of predictive validity for psychiatric syndromes. It is an under-studied area despite its clinical and research implications. This report aimed to critically review the literature concerning diagnostic stability in functional psychosis. Methods: Articles concerned with evaluating the diagnostic stability of functional psychosis and factors associated with diagnostic change were reviewed. Results: Despite methodological variation, schizophrenia was found to be the most stable diagnosis followed by affective psychosis. Other psychotic disorders were diagnostically unstable overtime. Around one-fifth of patients with first-onset psychosis had their diagnoses revised at follow-up. Diagnostic change occurred early in the course of the psychotic illness. The major pattern of diagnostic shift was towards schizophrenia spectrum disorders, particularly schizophrenia. Few variables were identified as predictors of such diagnostic conversion and the evidence established thus far is inconclusive. Conclusions: The present analysis indicates that diagnostic uncertainty and temporal instability is common in the early phase of psychosis especially in less prevalent diagnostic categories. It also highlights the limitations of the contemporary nosological classification in functional psychosis. In the absence of biological markers, a diagnostic process taking into account longitudinal observations across consecutive episodes should be a major requirement for making a definitive diagnosis. © 2009 Hong Kong College of Psychiatrists.