This article reviews recent evidence on changes over time in the direct medical costs of treating three of the more common mental health disorders in the US: the acute (16-week) phase of major depressive disorder, the ongoing treatment of schizophrenia, and the ongoing treatment of bipolar I disorders. The three studies discussed in this article cover various time intervals over the decade from 1991 through 2000, and encompass both private sector and governmental funding sources. Although there has been a shift over time away from intensive psychosocial/psychotherapy and towards increasingly expensive psychopharmacotherapy for all three disorders, total direct medical costs of treatment for each of these three mental health disorders have been declining over time. However, a substantial portion of treatment is not supported by clinical evidence.