Background: Bipolar disorder (BD) may be associated with significant and persistent cognitive impairment. The aim of this study was to describe the profile of cognitive deficits in BD at different phases of the illness and determine whether it is different from that of schizophrenia and unipolar (UP) depression.
Methods: A systematic review of the computerised literature of neuropsychological studies of BD published between 1980 and 2000.
Results: General intellectual function: this was largely preserved in BD. Impairments when present were limited to acute episodes and to performance scores. Attention: attentional abnormalities were seen in symptomatic BD patients and persisted in remission in measures of sustained attention and inhibitory control. Memory: verbal memory was impaired even in euthymic patients while visuo-spatial memory deficits were variable depending on the tasks used. Executive function: all aspects of executive function (planning, abstract concept formation, set shifting) were impaired in symptomatic BD patients. Performance on executive function tests was sensitive to the presence of even residual symptoms but it may be normal in fully recovered patients with uncomplicated BD. Comparison to other patient groups: no major differences in cognitive profile between BD and UP depression were found. Remitted BD patients out-performed stable schizophrenics on most cognitive measures but this advantage disappeared when they were acutely symptomatic.
Conclusions: Symptomatic BD patients have widespread cognitive abnormalities. Trait related deficits appear to be present in verbal memory and sustained attention. Executive function and visual memory may be also affected at least in some recovered BD patients.