The role of predominant polarity on cognitive dysfunctions in patients with bipolar disorder.

Background: Cognitive impairment is frequently observed in bipolar disorder (BD). Previous findings indicated that predominant polarity could have an effect on cognitive deficits. This study aimed to examine the association between predominant polarity and cognitive impairments in BD.

Materials and methods: Euthymic BD patients with manic (MPP, n = 31), depressive (DPP, n = 25), undetermined predominant polarity (UPP, n = 28), and healthy controls (HC, n = 27) participated in the study. A battery of neurocognitive and social cognitive tests was implemented. Neurocognitive domains were identified via principal component analysis.

Results: The MPP group performed worse in the Controlled Oral Word Association Test (COWAT), Reading the Mind in the Eyes Test (RMET), and Hinting Test (HT) compared to the DPP group and reasoning/problem-solving skills compared to the UPP group. Both MPP and UPP groups showed impairments in processing speed compared to HC. Among patient groups, there was no significant difference in working memory, attention, processing speed, verbal, and visual domain scores. The MPP group had poorer scores compared to controls in most of the social cognitive and neurocognitive domains in the study, while the overall cognitive impairment in the DPP group was relatively milder.

Conclusions: Although our sample size was relatively small, the MPP group yielded more severe cognitive impairment in verbal fluency and social cognition tests compared to DPP. Patients with MPP are particularly vulnerable to cognitive impairment, making them a priority for cognitive enhancement interventions. Future studies should focus on the outcomes of cognitive and pharmacological interventions in these polarity subgroups.