"We believe," he added, "that cost savings occur because improving depression allows patients to better manage their self-care regimens for diabetes -- taking medication, following diet and exercising."

Katon, from the University of Washington School of Medicine in Seattle and colleagues, came to this conclusion after studying data for a subset of patients who participated in a randomized trial of an intervention to improve access to care for depression in elderly patients.

Researchers noted a large increase in depression-free days over a 2-year period with only a slight increase in medical costs in subjects assigned to depression intervention compared to those assigned to usual care.

Intervention patients had 115 more depression-free days than usual care patients. The total outpatient costs in the intervention group were only $25 higher.

In addition, using measures that included value to the patients as well as value to the medical system, the team calculated that the incremental net benefit of the depression intervention amounted to more than $1,100.