Time-related cognitive deficiency in four different types of depression

Mild cognitive impairment often occurs in depressive illness. But it is unknown whether the occurrence or severity of cognitive deficits has diagnostic specificity. It is of interest to investigate whether there are time-related differences in cognitive functions characteristic of different kinds of depressive diagnoses, and therefore whether such differences might help to distinguish between types of depressive disorder. Eighty inpatients with a DSM-IV depressive episode (unipolar, bipolar, dysthymic and schizoaffective disorder, depressive type) were assessed with a series of neuropsychological tests at the beginning and at the end of their hospital stays. A group of 62 matched healthy controls were assessed with the same series of tests at comparable intervals. The diagnostic sub-groups could not be distinguished by cognitive parameters in the time-course. At the time of admission the inpatient group had a worse performance than the control group. After a significant decrease of their mean depression score, the patients still continued to show an outcome worse than the controls. We conclude that the variation of cognitive dysfunction with time in depression seems to be a phenomenon which does not depend on the kind of depressive sub-diagnosis. The results indicate that cognitive deficits might persist longer than the period of illness, but this seems to be true for all depressive sub-diagnoses.