Background The Norwegian Knowledge Centre for the Health Services was asked by Helse Sør-Øst RHF (South-Eastern Norway Regional Health Authority) to review research about the effects of long-term institutional treatment of patients with substance abuse compared with short-term outpatient treatment.

Objective The objectives were to assess the effectiveness of; 1) long-term treatment of patients with substance abuse compared to short-term treatment and 2) to estimate the cost-effectiveness of long-term treatment compared to short-term treatment.

Methods We searched systematically for systematic reviews, randomised controlled trials and cohort studies in international databases. We appraised and synthesized studies that met our inclusion criteria.

Results We included one systematic review and five studies, three cohort studies and two health economy evaluations in our review. Although residential treatment may offer some specific advantages, the conclusion here is that improvement among day treatment clients was not significantly different from that of residential treatment clients. Few baseline predictors were prospectively related to relapse at 12 and 18 months. Results from health economic evaluations suggest that outpatient and short-term residential treatments might be cost effective compared to long-term residential treatment.

Conclusion Our systematic review gave no compelling evidence to support long term treatment over short term interventions for drug addiction. However, it was emphasized that the results must be interpreted carefully, because of low quality of economic studies. Results from new research may alter our conclusions.