This study of a mentally ill Medicaid population revealed that placing providers at financial risk successfully contained treatment costs; however, the authors note that such practices may also place other payers at risk including charities and individual payers. 

Jones, K., Chen, H. J., Jordan, N., Boothroyd, R. A., Ramoni-Perazzi, J., & Shern, D. L. (2006). Examination of the effects of financial risk on the formal treatment costs for a Medicaid population with psychiatric disabilities. Medical Care, 44(4), 320-7.**Note: An abstract link is not available for this citation. 

Authors: Kristine Jones, Jen Huey Chen, Neil Jordan, Roger A. Boothroyd, Josefa Ramoni-Perazzi, David L. Shern