Cognitive dysfunction in bipolar disorder

Purpose of review The present review focuses on recent neuropsychological assessments in bipolar disorder, the methodological issues concerning such studies and areas for future investigation. Recent findings A range of neuropsychological deficits has been demonstrated in manic and depressed patients. However, nonspecific factors may confound such studies. Neuropsychological assessments of euthymic bipolar patients suggest that deficits persist during remission. However, there is debate as to how best conceptualise such 'trait' deficits. Similar neuropsychological deficits have been reported in bipolar disorder and in schizophrenia, which has potential nosological implications. The temporal evolution of neuropsychological deficits is unclear. Deficits have been associated with illness progression. However a few recent studies provide evidence of selective neuropsychological deficits in high-risk groups in bipolar disorder. The neural correlates inferred from neuropsychological studies are consistent with reports from functional neuroimaging and neuropathological studies which have identified prefrontal cortex disturbance and disruption of frontostriatal circuits in bipolar disorder. Summary Persistent cognitive impairment in bipolar disorder challenges long-held views on the nature of the disorder. Clarification of the cognitive profile is necessary but will require well-constructed, methodologically robust studies. Further investigations in high-risk groups may help to clarify the development and cause of cognitive dysfunction in bipolar disorder.