Cognitive impairments and predominant polarity in bipolar disorder: a cross-sectional study

Background: Bipolar disorder (BD) patients exhibit cognitive impairments during euthymic states. Studies suggest that manic episodes may be correlated to cognitive impairments. The present study investigated the relationship between predominant polarity and the cognitive deficits frequently detected in bipolar patients. We hypothesize that mania predominant polarity (MPP) patients should exhibit greater cognitive impairments in comparison to depressive (DPP) and indefinite predominant polarity (IPP) patients and healthy control (HC) individuals. Methods: The study evaluated 55 euthymic BD patients, type I and II, and 31 HCs. Patients were divided into 3 groups: MPP (n = 17), DPP (n = 22), and IPP (n = 16), and compared regarding demographic and clinical variables, and performance on a 7-test neuropsychological battery. Results: MPP patients demonstrated greater cognitive impairments in alternating attention, verbal fluency, and delayed memory in comparison to DPP, IPP, and HC. Compared to HC, IPP patients exhibit cognitive deficits in verbal fluency and alternating attention and DPP patients solely in verbal fluency. Furthermore, DPP patients did not exhibit, in none of the seven neuropsychological tests, significant poorer performances than MPP or IPP patients, although having significant more episodes than MPP patients. Conclusion: MPP patients exhibit increased cognitive impairments in comparison to DPP, IPP, and HC subjects. Manic episodes may play an important role in the development of cognitive deficits and thus, in potential neuroprogression. Predominant polarity may be an important specifier for predicting future cognitive impairments.