A systematic review and meta-analysis on the effects of European drug treatment programmes on reoffending

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.