Cognitive impairment in euthymic bipolar patients: implications for clinical and functional outcome

Abstract

Objective: Cognitive impairment in bipolar disorder may be a stable characteristic of the illness, although discrepancies have emerged with regard to what dysfunctions remain during remission periods. The aim of this study was to ascertain whether euthymic bipolar patients would show impairment in verbal learning and memory and in executive functions compared with healthy controls. Secondly, to establish if there was a relationship between clinical data and neuropsychological performance. Methods: Forty euthymic bipolar patients were compared with 30 healthy controls through a battery of neuropsychological tests assessing estimated premorbid IQ, attention, verbal learning and memory, and frontal executive functioning. The effect of subsyndromal symptomatology was controlled. Results: Remitted bipolar patients performed worse than controls in several measures of memory and executive function, after controlling for the effect of subclinical symptomatology, age and premorbid IQ. Verbal memory impairment was related to global assessment of function scores, as well as to a longer duration of illness, a higher number of manic episodes, and prior psychotic symptoms. Conclusions: Results provide evidence of neuropsychological impairment in euthymic bipolar patients, after controlling for the effect of subsyndromal depressive symptoms, suggesting verbal memory and executive dysfunctions. Cognitive impairment seems to be related to a worse clinical course and poor functional outcome.