Objective: Diagnostic shifts have been prospectively examined in the short term, but the long-term stability of diagnoses has rarely been evaluated. The authors examined diagnostic shifts over a 10-year follow-up period.
Method: A cohort of 470 first-admission patients with psychotic disorders was systematically assessed at baseline and at 6-month, 2-year, and 10-year follow-ups. Longitudinal best-estimate consensus diagnoses were formulated after each assessment.
Results: At baseline, the diagnostic distribution was 29.6% schizophrenia spectrum disorders, 21.1% bipolar disorder with psychotic features, 17.0% major depression with psychotic features, 2.4% substance-induced psychosis, and 27.9% other psychoses. At year 10, the distribution changed to 49.8%, 24.0%, 11.1%, 7.0%, and 8.1%, respectively. Overall, diagnoses were changed for 50.7% of study participants at some point during the study. Most participants who were initially diagnosed with schizophrenia or bipolar disorder retained the diagnosis at year 10 (89.2% and 77.8%, respectively). However, 32.0% of participants (N=98) originally given a non-schizophrenia diagnosis had gradually shifted to a schizophrenia diagnosis by year 10. The second largest shift was to bipolar disorder (10.7% of those not given this diagnosis at baseline). Changes in the clinical picture explained many diagnostic shifts. In particular, poorer functioning and greater negative and psychotic symptom ratings predicted a subsequent shift to schizophrenia. Better functioning and lower negative and depressive symptom ratings predicted the shift to bipolar disorder.
Conclusions: First-admission patients with psychotic disorders run the risk of being misclassified at early stages in the illness course, including more than 2 years after first hospitalization. Diagnosis should be reassessed at all follow-up points.