Effects of adjunctive memantine on executive function and global cognition in bipolar disorder (BD): A randomized, double-blind, placebo-controlled clinical trial.
BACKGROUND: Cognitive impairment contributes substantially to disability in bipolar disorder (BD), but effective pharmacologic options remain limited. This trial evaluated whether adjunctive memantine improves global cognition and executive function in BD. METHODS: In this double-blind, placebo-controlled randomized trial, patients with bipolar I disorder (B1D) receiving lithium and olanzapine were assigned to memantine or placebo. Memantine was titrated to 20 mg/day over 6 weeks. Cognitive outcomes were assessed at baseline, week 6, and week 18. Global cognition was measured with the Neurocognitive Assessment Battery (NuCog), and executive function with the Frontal Assessment Battery (FAB). Data were analyzed using generalized estimating equations and Bonferroni-adjusted post-hoc tests. RESULTS: Sixty-three participants were randomized (memantine, n = 31; placebo, n = 32), and all completed follow-up. Groups were comparable at baseline for demographic and clinical variables and for most cognitive measures. Both groups improved over time (P < 0.001), but improvement was greater with memantine for global cognition at week 6 (MD = 9.32; 95% CI, 4.84-13.81; P < 0.001) and week 18 (MD = 12.69; 95% CI, 8.67-16.71; P < 0.001). FAB total scores favored memantine at week 18 (MD = 2.68; 95% CI, 1.76-3.61; P < 0.001), but not at week 6. Domain analyses showed significant benefits for NuCog attention, visuoconstructional ability, memory, and executive function, and for several FAB subscales by week 18. CONCLUSIONS: Adjunctive memantine improved global cognition and, over longer follow-up, executive function in BD. These findings support NMDA receptor modulation as a potential strategy for cognitive dysfunction in BD.