Introduction: Cognitive functioning is one of the effective factors in treatment, progression, prognosis and quality of life in bipolar patients. In the present study, cognitive effects of lithium and valproate which used as first line treatment for bipolar disorder were compared.

Methods: 90 patients meeting DSM-IV-TR criteria for acute mania were selected with easy sampling. Diagnosis of acute mania was established by clinical interview. From patients,40 were on treatment with lithium and 50 on valproate by another psychiatrist without interference of researchers. All patients were evaluated by Young Mania Rating Scale(YMRS), Clinical Global Impression(CGI) and cognitive assessment was done through these tests: letter and semantic Controlled Oral Word Association Test(COWAT), Rey Auditory Verbal Learning Test(RAVELT), Backward Digit Span Subset(BWDST), Symbol Digit Modalities Test(SDMT) and Trial Making Test(TMT) before the beginning of treatment and 3weeks later.

Results: All patients showed improvement in cognitive functioning with no significant difference between two groups(p=0.6). Women on lithium showed better function in working memory(p=0.02) and processing speed(p<0.001) than men. YMRS and CGI numbers were decreased significantly however the difference between two groups was not significant.

Conclusion: Benefits of lithium and sodium valproate in short term treatment of acute mania significantly more than their adverse cognitive effects. The positive effect of these drugs on control of psychotic and affective symptoms lead to improvement of cognitive statement in these patients without significant difference between lithium and valproate.