This article examines the effects of integrating medical and substance abuse treatment on health care utilization and cost. The authors find that there were no significant between the two treatment groups over time but that, for the subgroup of patients with substance abuse related medical conditions, decreased other health care utilization and reduced total medical costs per-month from $431 to $200.  The authors concluded that integrated care may not be suited for all patients but appears beneficial for a subset of substance abusers.   

Parthasarathy, S., Mertens, J., Moore, C., & Weisner, C. (2003). Utilization and cost impact of integrating substance abuse treatment and primary care. Medical Care, 41(3): 357-367. http://www.ncbi.nlm.nih.gov/pubmed/12618639 

Authors: Sujaya Parthasarathy, Jennifer Mertens. Charles Moore, Constance Weisner