Forty subjects with bipolar disorder who are not receiving a mood-stabilizing medication for the treatment of their illness will participate in this study. The study aims to evaluate how decision-making is affected by treatment for bipolar disorder. Prior to beginning treatment, patients will complete questionnaires and a one-hour computer-administered assessment of decision-making. Differences between pre-post decision-making outcomes will be evaluated to examine whether the neuroeconomic concepts of risk aversion, loss aversion, risk tolerance and delay discounting are affected by treatment.