Drug treatment programmes

Koehler et al. (2014) carried out a systematic review and meta-analysis of the effects of drug treatment programmes in Europe on reoffending. The majority of studies included in the review originated in the United Kingdom and described substitution therapy-based treatment, in which substitute medication is prescribed to counter withdrawal symptoms with reducing levels or abstaining from substance abuse. The review authors identified a limited number of high-quality European programme evaluations, all of which highlighted positive effects of treatment programmes or reducing reoffending. Further high-quality research is needed on specific topics and offender populations, and also to evaluate the efficacy of other forms of intervention, such as therapeutic communities or cognitive-behavioural programmes.

Studies reviewed

Average impact

Certainty of impact


System readiness


Positive effect


Not evaluated


What is it?

Drug treatment programmes are designed to address behaviours associated with substance abuse. Programmes vary and include pharmacological treatments (e.g. substitution based methods), therapeutic communities, counselling and cognitive-behavioural interventions, and drug court interventions.

Should it work?

Given the intervention modalities, many of which focus on psychosocial support, it is expected that drug treatment programmes would effectively benefit substance abusers in a number of ways, including social, mental and physical health related outcomes.

There is also evidence to suggest a relationship between substance abuse and offending. For example, Bennett, Holloway and Farrington (2009, cited by Koehler et al., 2014) carried out a meta-analysis and found that the odds of offending were 2.8 to 3.8 times greater for individuals who used drugs, with greater odds for those using addictive (rather than recreational) substances. Whilst it is important however not to assume a simple linear causal relationship (i.e. that substance abuse causes offending), it is rational to explore the possibility that reducing substance misuse may result in a reduction in offending. For example, an offender who reduces or eliminates their addiction may no longer need to commit theft to fund that addiction. Indeed, there is a long history of using different kinds of drug treatment programmes with offenders, with associated empirical evidence suggesting reductions in offending (Koehler et al., 2014).

Does it work?

Yes. Both the systematic review of individual studies and the overall meta-analysis demonstrate that there is consistent high-quality evidence that this treatment has a positive effect on reducing reoffending. Based on an assumed 50% base rate for reoffending, the meta-analysis results suggest a 37% reduction in recidivism amongst individuals participating in a substance addiction treatment programme, compared with those receiving no treatment, or treatment-as-usual (e.g. “a custodial sanction without the respect drug-oriented programme” – Koehler et al., 2014).

The review also found that pharmacological treatment programmes (e.g. substitution) were associated with greater reductions in reoffending than other types of programme. However this finding needs to be interpreted cautiously due to the small number of studies of under comparison.

One finding with particular relevance to practitioners is that individuals who complete treatment are associated with better outcomes (in terms of reduced reoffending) than those who do not. This suggests that practitioners should prioritise effort towards ensuring that individuals have the best possible chance of completing treatment, for example by motivating them and making treatment programmes accessible.

How strong is the evidence?

The review is based on mainly small scale research with the largest total participant size being 1205 (Martin et al., 2003, cited by Koehler et al., 2014) and the smallest total participant size being 37 (Strang et al., 2000, cited by Koehler et al., 2014).


It is noteworthy that although a small number of studies (n=15) was included in the review, these were based on research designs which provide a high degree of internal validity and causal inference. In other words, the research designs provide confidence that the intervention (rather than other factors) was responsible for the observed effect on reoffending.

Is it worth it?

Koehler et al. (2014) did not undertake a comprehensive economic analysis as part of their review, but based on their meta-analysis suggested probable human and financial benefits associated with a 37% reduction in recidivism.

Can it be implemented?

Yes. There is evidence from practice and from the systematic review that drug treatment programmes can be implemented. The review identified some factors which may be associated with implementation (e.g. attrition), which may have an effect of reducing reoffending. This suggests that although the skills and resources exist to implement drug treatment programmes, high-quality interventions are likely to be associated with better outcomes in terms of reoffending.

What’s missing from the evidence?

The evidence from the review primarily concerned substitution therapy, and therefore does not reflect the full range of drug treatment programmes used in the criminal justice sector. Additional reviews of a larger number of comparable programmes would further develop the evidence base. To facilitate this Koehler et al. (2014) call for more good quality drug treatment programme evaluations from most European countries, including for different offender populations (e.g. young offenders, female offenders), and for a wider range of substances.


Koehler, J. A., Humphreys, D. K., Akoensi, T. D., de Ribera, O. S., & Loesel, F. (2014). A systematic review and meta-analysis on the effects of European drug treatment programmes on reoffending. Psychology Crime & Law, 20(6), 584–602. https://doi.org/10.1080/1068316X.2013.804921