"The evaluations we reviewed showed that adult drug-court program participation was also associated with reduced drug use. Our analysis of evaluations reporting relapse data for eight programs showed that drug court program participants were less likely than comparison group members to use drugs, based on drug tests or self-reported drug use, although the difference was not always significant.42 This was true for both within-program and post-program measures, and whether drug use was reported as the difference in the frequency of drug use or the proportion of the treatment and comparison groups who used drugs."

Source

"Adult Drug Courts: Studies Show Courts Reduce Recidivism, but DOJ Could Enhance Future Performance Measure Revision Efforts" (Washington, DC: Government Accountability Office, Dec. 2011), GAO-12-53, pp. 17-18.
http://www.gao.gov/assets/590…