Neuropsychological functioning in euthymic bipolar disorder: a meta-analysis

OBJECTIVE: Although cognitive deficits are prominent in symptomatic patients with bipolar disorder, the extent and pattern of cognitive impairment in euthymic patients remain uncertain. METHOD: Neuropsychological studies comparing euthymic bipolar patients and healthy controls were evaluated. Across studies, effect sizes reflecting patient-control differences in task performance were computed for the 15 most frequently studied cognitive measures in the literature. RESULTS: Across the broad cognitive domains of attention/processing speed, episodic memory, and executive functioning, medium-to-large performance effect size differences were consistently observed between patients and controls, favoring the latter. Deficits were not observed on measures of vocabulary and premorbid IQ. CONCLUSION: Meta-analytic findings provide evidence of a trait-related neuropsychological deficit in bipolar disorder involving attention/processing speed, memory, and executive function. Findings are discussed with regard to potential moderators, etiologic considerations, limitations, and future directions in neuropsychological research on bipolar disorder.