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Abstract
This article presents the results of a systematic review and meta-analysis on the effects of treatment programmes for drug abusing offenders in Europe, using stringent eligibility criteria to control for threats to internal validity. A literature search of approximately 37,000 titles revealed 15 sound evaluations from six countries, containing 3953 participants. There were significant positive overall effects of treatment on crime (d=0.47) and illicit drug use (d=0.38). Most evaluations originated from the UK and evaluated primarily substitution therapy-based treatment. Evaluations of other interventions were a minority. Our findings support the use of treatment programmes among substance-abusing offenders. However, these results are limited to a small set of programmes from very few countries. Therefore, sound evaluations on a range of treatments across Europe are needed.
Acknowledgements
This study was carried out within the European cooperation project ‘Strengthening Transnational Approaches to Reducing Reoffending’, which was funded by the European Union. We thank our partners from the UK Ministry of Justice, London Probation Trust, European Organization for Probation, and the Ministries of Justice of Bulgaria, France and Hungary for their cooperation. We also thank primary study authors for providing us with the data to assist in the meta-analysis.
Notes
1. A full list of the search terms employed in our search and the list of databases with their corresponding number of hits can be found in Appendices 1 and 2, respectively.
2. Robertson et al. (Citation2006) observed a crime outcome of 0.01, which is more sensibly interpreted as a non-effect, rather than a positive effect.
3. Mitchell et al. (Citation2006) report an overall drug relapse score of OR=1.28. This was converted to Cohen's d using the formula found in Chinn (Citation2000).