This study compares Medicaid reimbursement costs for enrollees with substance abuse diagnoses that did and did not receive substance abuse treatment.  The study found that the average monthly costs for untreated patients were higher ($257) in the year prior to diagnosis than for those who were treated ($207) and that monthly costs in the six months following identification were $761 for the untreated and $373 for the treated while the costs in the next six months returned to near the original for the treated ($224), while those for the untreated remained higher at $340.  The authors conclude that untreated substance abusers pose a significant cost to the Medicaid system. 

Gerson, L. W., J. Boex, et al. (2001). Medical care use by treated and untreated substance abusing Medicaid patients. Journal of Substance Abuse Treatment, 20(2): 115-20. http://www.journalofsubstanceabusetreatment.com/article/S0740-5472%2800%2900154-9/abstract 

Authors: Lowell W. Gerson, James Boex, Keding Hua, Robert A. Liebelt, William R. Zumbar,Donna Bush, Carolyn Givens