This study examines outcomes and cost savings of drug and alcohol treatment in Oregon. 

From the report:

Treatment completion is associated with substantially fewer incarcerations in the state prison system and with fewer days of incarceration. For example, residential treatment completers were incarcerated at a rate of 70% lower than the matched group.  In the period subsequent to treatment, treatment completers received 65% higher wages than those who didn't ’t complete treatment. This difference is due to improvement in earning power and in number of weeks worked. The use of food stamps was reduced significantly for clients who completed treatment compared with those who were non-completers. Completers had only one-third the use of food stamps experienced by the early-leaver comparison group. For clients who completed treatment, open child welfare cases decreased by 50% subsequent to treatment.  Medical expenses were substantially lower for those who completed treatment compared with the control group. For example, early-leavers showed a dramatic increase in the use of hospital emergency rooms during the period following treatment compared with the treatment group. The 1991–92 cohort of treatment completers produced cost savings of $83,147,187 for the two and a half years following treatment. The cost for treating all adults in 1991–92 was $14,879,128. Thus, every tax dollar spent on treatment produced $5.60 in avoided costs to the taxpayer.

Full report: Societal Outcomes and Cost Savings of Drug and Alcohol Treatment in the State of Oregon (PDF|96KB)

NPC Research Inc. for Office of Alcohol and Drug Abuse Programs, Oregon Department of Human Resources. (1996). Societal outcomes and cost savings of drug and alcohol treatment in the state of Oregon. Finigan, M.