This is a randomized, double-blind, placebo-controlled, multicentre, parallel-group study to assess the cognitive effects of lurasidone in bipolar I and II patients (manic depression) who are in remission from an episode. Participants who show cognitive impairment at the screening visit will be enrolled into the study and randomized at the baseline visit to receive either lurasidone or placebo adjunctive therapy in a 1:1 ratio for 6 weeks.