BackgroundDiabetes is one of the most prevalent chronic diseases with subsequent complications. The positive effects of diabetes pay-for-performance (P4P) programs on treatment outcomes have been reported. The program provides financial incentives based on physiological care indicators, but common mental disorder complications such as depression are not covered.MethodsThis study employed a natural experimental design to examine the spillover effects of diabetes P4P program on patients with nonincentivized depressive symptoms. The intervention group consisted of diabetes patients enrolled in the DM P4P program from 2010 to 2015. Unenrolled patients were selected by propensity score matching to form the comparison group. Difference-in-differences analyses were conducted to evaluate the effects of P4P programs. We employed generalized estimating equation (GEE) models, difference-in-differences analyses and difference-in-difference-in-differences analyses to evaluate the net effect of diabetes P4P programs. Changes in medical expenses (outpatient and total health care costs) over time were analysed for the treatment and comparison groups.ResultsThe results showed that enrolled patients had a higher incidence of depressive symptoms than unenrolled patients. The outpatient and total care expenses of diabetes patients with depressive symptoms were lower in the intervention group than in the comparison group. Diabetes patients with depressive symptoms enrolled in the DM P4P program had lower expenses for depression-related care than those not enrolled in the program.ConclusionsThe DM P4P program benefits diabetes patients by screening for depressive symptoms and lowering accompanying health care expenses. These positive spillover effects may be an important aspect of physical and mental health in patients with chronic disease enrolled in disease management programs while contributing to the control of health care expenses for chronic diseases.