Prison-based chemical dependency treatment in Minnesota: An outcome evaluation

Using a retrospective quasi-experimental design, this study evaluated the effectiveness of prison-based chemical dependency (CD) treatment by examining recidivism outcomes among 1,852 offenders released from Minnesota correctional facilities during 2005. Because recidivism data were collected on the 1,852 offenders through the end of 2008, the average follow-up period was 42 months. To minimize the threat of selection bias, propensity score matching was used to create a comparison group of 926 untreated offenders who were not, for the most part, significantly different from the 926 treated offenders. Results from the Cox regression analyses revealed that participating in prison-based CD treatment significantly reduced the hazard ratio for recidivism by 17-25%. Although dropping out of treatment did not increase the risk of recidivism, completing treatment significantly lowered it by 20-27%. The findings also suggest that long-term treatment programs were not as effective as short- or medium-term programs in reducing the risk of recidivism. The study concludes by discussing the implications of these findings.