Objectives-Neuropsychological studies in subjects with bipolar disorder (BD) have reported deficits on a variety of cognitive measures. However, because the majority of subjects were medicated at the time of testing in previous studies, it is currently unclear whether the pattern of deficits reported is related to BD itself or to psychotropic medication. We addressed this issue by examining cognitive performance in a group of unmedicated, currently depressed subjects with BD.Methods-Forty-nine unmedicated subjects who met DSM-IV criteria for BD, depressed phase, and 55 control subjects participated in this study. Most patients were diagnosed with bipolar II disorder. Performance on emotion-dependent, or 'hot', and emotion-independent, or 'cold', cognitive tasks was assessed using tests from the Cambridge Neuropsychological Test Automated Battery.Results-The groups were well matched with respect to general intelligence and demographic variables. Deficits in the unmedicated depressed BD group were apparent on tests tapping 'hot' cognitive processing, for example the Cambridge Gamble task and the Probabilistic Reversal Learning task. However, other than a deficit on the Spatial Span test in the depressed BD subjects, the groups performed equivalently on most measures of 'cold' cognitive processing, for example visual memory, attention, and working memory.Conclusions-These data suggest that deficits on tests involving reward processing, short-term spatial memory storage, and sensitivity to negative feedback in depressed BD subjects represent an effect of the illness itself and not mood-stabilizing medication.
NIH-PA Author ManuscriptNIH-PA Author Manuscript
NIH-PA Author ManuscriptMost of the published neuropsychological investigations of cognitive function in bipolar disorder (BD) have been confounded by the effects of medication. While some studies reported that medicated subjects with BD performed worse than matched controls on a number of neuropsychological tests (1-5, see 6 for a review), it remains unclear whether these deficits are present in unmedicated subjects. Furthermore, while recent studies have reported less pronounced cognitive impairment in patients with bipolar II disorder (BD-II) than bipolar I disorder (BD-I) (3,7-10), in some studies BD-II patients had a different profile of medication than those with 8). The aim of this study was to determine whether cognitive impairment is observed in unmedicated subjects with BD in a group primarily comprising patients with a diagnosis of BD-II.There is some evidence that mood-stabilizing medications, such as lithium, might themselves result in cognitive impairment. While a recent review concluded that the net effect of lithium administration was probably protective (11), it has long been known that patients using such medications report a dulling of intellectual capacity and concentration difficulties (12), and a meta-analysis concluded that lithium administration may negatively affect motor speed and verbal memory (13). Furthermore, studies adminis...
