Our understanding of optimal treatment for depression in diabetic patients is evolving. At present, it is best understood as a process requiring simultaneous comprehensive care of both medical and psychiatric illness aspects. A recent meta-analysis determined that treatment of depression in diabetes could increase the proportion of diabetic patients in good glycemic control from 41 to 58%. 53 The projected improvement in optimal glycemic control would have significant individual and societal benefits in terms of outcomes related to complications, quality of life, and health care expenditures. We reviewed here evidence in support of a hypothesis that relief of depression may improve the medical prognosis, delaying development or slowing progression of diabetes. We think it important that both patients and providers recognize the implications of the hypothesis for individuals and for society: the genuine possibility that treatment of depression may promote health, even extend life. At the same time we recognize the limited nature of the evidence presented and the somewhat speculative character of our argument. Apart from its effects on specific diabetes end points, depression remains an important focus of clinical care because of its beneficial effects on mood, functioning, and quality of life.