Admission pattern and diagnostic stability among unipolar and bipolar manic-depressive patients

The instability of the diagnoses in a psychiatric register causes practical problems when groups of probands with specific diagnoses are selected for further studies. A cohort of 3,062 first admissions with at least one manic-depressive admission was followed for 5-7 years. 623 had at least one admission for mania and were considered bipolar. The percentage of patients who changed their diagnoses was highest at first readmission; at each later readmission about 10% of the bipolars and 25% of the unipolars changed from manic-depressive psychosis and a similar number changed from other diagnoses to manic-depressive psychosis. Compared with the diagnostic distribution of all register cases, reactive psychoses were more frequent than expected as former diagnoses and schizophrenia as later diagnosis. Neuroses and character deviations were frequent alternative diagnoses among unipolars, not among bipolars. The consequences of different selection criteria for the composition of proband groups are discussed.