Bipolar Disorder Pills in Perspective: Questions From Peer Review

I recently performed a peer review of a manuscript submitted for consideration for publication in the Journal of Managed Care Pharmacy (JMCP) on the subject of the total costs of care for patients with bipolar disorder treated with divalproex versus one of 3 atypical antipsychotics; 2 different classes of medications were involved. In this regard, a point arose that divalproex treats mania but not depression in the condition singularly labeled as bipolar disorder. So, pitting the 2 classes against one another may not be appropriate unless one can argue that both classes treat the same problem. To a neurologist, the question is: What is the actual defect?