"Based on our analyses mainly of the self-report data, we find that drug courts were effective in reducing substance abuse relapse. Six months after entering drug court, program participants averaged fewer days of drug use per month (1.5 vs. 3.7 days; p < .01) and fewer days of serious drug use per month (1.0 vs. 2.2 days, p < .05) than the comparison group. By the 18-month follow up, the drug court cohort had significantly fewer occurrences of any drug use (56 percent vs. 76 percent, p < .01), serious use (41 percent vs. 58 percent, p < .01), days of use per month (2.1 vs. 4.8, p <.001), and days of serious use per month (1.1 vs. 2.3; p < .001). Regarding specific substances, drug court participants were significantly less likely than the comparison members to report use of marijuana, alcohol, 'heavy' use of alcohol, illegal use of prescription drugs, and illegal use of methadone; there were no significant differences between the two groups for cocaine, heroin, amphetamines, and hallucinogens, although the differences reported trended in the direction of less use by the drug court sample.
"Additionally, statistically significant percentages of drug court participants report no relapse during the 18-month period; similarly, drug court participants were statistically significantly less likely to relapse in the first six months. Conversely, a small, but statistically significant, percentage of the comparison group reported no sobriety within the 18 months."

Source

Rossman, Shelli B., et al., "Final Report, Volume 4: The Multi-Site Adult Drug Court Evaluation: The Impact of Drug Courts" (Washington, DC: Urban Institute, June 2011), p. 57.
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