Cognitive function in euthymic bipolar patients, stabilized schizophrenic patients, and healthy controls

Studies on cognitive function in bipolar disorder have led to contrasting r esults and few data are available on affected subjects during the euthymic phase. In the present study we investigated the cognitive function of a coh ort of bipolar (n = 40) and schizophrenic (n = 66) patients compared to hea lthy controls (n = 64). Patients were evaluated in the outpatient setting o ver at least 3 months using a computerized version of Wisconsin Card Sortin g Test. Schizophrenic patients showed the worst performance while that of t he bipolar patients was somewhere between schizophrenic and controls. A dis criminant analysis was able to classify correctly 60.59% of the subjects (s chizophrenics 48.5%, bipolars 40%; healthy controls 85.9%). The scores of t he Wisconsin Card Sorting Test were entered into a principal component anal ysis, which yielded a 2-factor solution. Even in that analysis bipolar pati ents showed intermediate features in comparison with the other groups. Thes e data indicate that bipolar patients have subtle neurocognitive deficits e ven after the resolution of an affective disorder. As well as observing qua ntitative differences between groups, the results show different dimensions of cognitive performance within groups suggesting that the deficit of euth ymic bipolars could be a dishomogeneous entity, probably more heterogeneous than that in schizophrenia. Studies administering a more complete neuropsy chological battery could further clarify the nature and meaning of the cogn itive deficits in schizophrenia and bipolar disorder. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.