Neuropsychological performance in depressed and euthymic bipolar patients

Recent studies have suggested that the presence of persistent cognitive dysfunctions in bipolar patients is not restricted to acute episodes, but they persist even during remission states. Nevertheless, there are several methodological pitfalls in most studies, such as unclear remission criteria, diagnostic heterogeneity or small sample sizes.

Several domains of cognitive function were examined in 30 depressed bipolar patients [DSM-IV criteria for major depression, Hamilton Depression Scale (HDRS) > or =17] and 30 euthymic bipolar patients (at least 6 months of remission, HDRS < or =8 and Young Mania Rating Scale, YMRS < or =6). Psychosocial functioning was assessed through General Assessment of Functioning.

The two groups showed a similar pattern of neuropsychological performance. However, the depressed group was significantly impaired on the Controlled Oral Word Association Test, FAS (COWAT), a measure of verbal fluency, compared with the euthymic group. On the other hand, functional outcome in euthymic patients was related to verbal fluency, even after controlling for residual depressive symptoms.

Neuropsychological performance was similar in both groups, except for verbal fluency, which was lower in the depressed group. Poor verbal fluency was related to a poor social outcome in euthymic patients. Further research including longitudinal designs aimed at evaluating changes in cognition in these patients is warranted.