Differential patterns of neuropsychological performance in the euthymic and depressive phases of bipolar disorders

Aims: Patients with bipolar disorders (BD) show a broad range of neurocognitive impairments. We compared the patterns of neuropsychological performance in depressed and euthymic patients with BD, and explored the state-dependent cognitive markers of bipolar depression. Methods: The study participants included 32 BD patients (15 depressed and 17 euthymic) and 42 healthy controls. All of the subjects completed tests that assessed attention, psychomotor speed, verbal and visual memory, and executive functions. Between-group neuropsychological performance differences were examined. Multidimensional scaling (MDS) was used to compare the patterns of cognitive variables in euthymic and depressed BD patients. Results: Compared to the euthymic BD patients and healthy controls, the depressed BD patients performed lower in verbal memory and executive functions. No significant differences were found between the three groups in attention, psychomotor speed, and visual memory. The depressed BD patients showed a lower level of association between psychomotor speed and the time to initial concept formation than the healthy controls and euthymic BD patients. In contrast, the correlation between word association and verbal memory was stronger in the depressed group than either the control or euthymic groups. Conclusion: The depressed BD patients showed greater impairments in verbal memory and executive functions than the euthymic BD patients. In addition, our study identified a differential pattern of correlations between the cognitive domains of euthymic and depressed BD patients, which suggests the potential role of verbal memory and executive functions as cognitive markers of BD.