Change in the diagnosis is not uncommon among patients suffering from severe psychiatric disorders. Psychotic depression has shown an intermediate stability, whereas the results are conflicting concerning schizoaffective disorder. To have clinically useful predictive power a diagnostic description should have satisfactory stability. This follow-up study of psychiatric inpatients treated in Satakunta hospital district aimed to describe the stability of diagnosis in psychotic depression, schizoaffective disorder, depressive subtype and psychosis NOS, and to study factors associated with a change in diagnosis. Out of the 181 subjects in the study, 119 (65.7%) had a readmission during a minimum follow-up of eight years. The adjusted incidence of change in diagnosis in psychotic depression was 4.56-fold compared to schizoaffective disorder (p<0.001). Most patients (88.0%) with schizoaffective disorder retained their diagnosis, while more than two-thirds (68.7%) of those with psychotic depression had remained, although not psychotic, within the group of major depressive disorders. A non-affective schizophrenia group psychosis was the most common eventual diagnosis among the patients with a change in diagnosis.