This study measured the impact of substance abuse disorders on Medicaid expenditures among beneficiaries with M/SU conditions.  The study found that the impact of substance abuse on Medicaid enrollees with behavioral health conditions is greater than the direct cost of M/SU treatment.  While associated physical illness accounted form some of the higher costs; however, the expenditures remained higher after adjusting for disease burden.  The authors note that these findings indicate that M/SU cost estimates based only on behavioral health diagnoses may significantly under-estimate addiction-related costs.   

Clark, R. E., M. Samnaliev, et al. (2009). Impact of substance disorders on medical expenditures for Medicaid beneficiaries with behavioral health disorders. Psychiatric Services, 60(1): 35-42. DOI: 10.1176/appi.ps.60.1.35 http://psychservices.psychiatryonline.org/cgi/content/abstract/60/1/35 

Authors: Robin E. Clark, Mihail Samnaliev, Mark P. McGovern