Aim: Neurocognitive impairment is one of the core symptoms of bipolar disorder (BD). The MATRICS Cognitive Consensus Battery (MCCB) is a potential consensus assessment tool to evaluate cognitive function in patients with BD. Here, we report on cognitive deficits evaluated using the MCCB Japanese version (MCCB-J) in euthymic Japanese patients with BD, and compare them with scores in previous studies. Methods: We compared neurocognitive function in 25 patients with euthymic BD and 53 healthy controls (HC). Additionally, we searched all available databases for studies that have evaluated cognitive function in BD using the MCCB, and conducted a meta-analysis. Results: Canonical discriminant analysis revealed significant differences in MCCB-J domain scores between BD and HC. Patients with BD performed significantly worse on visual learning, social cognition, speed of processing, and MCCB composite scores. Our meta-analysis revealed that patients with BD performed worse than HC, as reflected by MCCB composite scores and scores on all seven cognitive domains. However, there are differences in the cognitive deficits identified in previous studies compared with our participants, particularly social cognition. Conclusion: As reported in previous studies, neurocognitive deficits were observed in Japanese euthymic BD patients assessed using the MCCB-J. Further study is needed to clarify whether differences in social cognition between this study and previous studies are a result of coping mechanisms for social settings in Japanese populations.
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