Diagnostic consistency and interchangeability of schizophrenic disorders and bipolar disorders: A 7‐year follow‐up study

Aim The change in psychiatric diagnoses in clinical practice is not an unusual phenomenon. The interchange between the diagnoses of schizophrenic disorders and bipolar disorders is a major clinical issue because of the differences in treatment regimens and long‐term prognoses. In this study, we used a nationwide population‐based sample to compare the diagnostic consistency and interchange rate between schizophrenic disorders and bipolar disorders. Methods In total, 25 711 and 11 261 patients newly diagnosed as having schizophrenic disorder and bipolar disorder, respectively, were retrospectively enrolled from the Psychiatric Inpatient Medical Claims database between 2001 and 2005. We followed these two cohorts for 7 years to determine whether their diagnoses were consistent throughout subsequent hospitalizations. The interchange between the two diagnoses was analyzed. Results In the schizophrenic disorder cohort, the overall diagnostic consistency rate was 87.3% and the rate of change to bipolar disorder was 3.0% during the 7‐year follow‐up. Additional analyses of subtypes revealed that the change rate from schizoaffective disorder to bipolar disorder was 12.0%. In the bipolar disorder cohort, the overall diagnostic consistency rate was 71.9% and the rate of change to schizophrenic disorder was 8.3%. Conclusion Changes in the diagnosis of a major psychosis are not uncommon. The interchange between the diagnoses of schizophrenic disorders and bipolar disorders might be attributed to the evolution of clinical symptoms and the observation of preserved social functions that contradict the original diagnosis. While making a psychotic diagnosis, clinicians should be aware of the possibility of the change in diagnosis in the future.