The Drug Treatment Outcomes Research Study (DTORS): final outcomes report.

Jones A., Donmall M., Millar T. et al.
[UK] Home Office, 2009.
Over 10 years since the last attempt, in 2006 a national study assessed the progress of patients starting drug treatment in England. A year later drug use and crime were down and social costs saved, but wider life improvements were minor compared to treatment costs.
Abstract: The Drug Treatment Outcomes Research Study (DTORS) was commissioned by the government  department with lead responsibility for drug policy and led by University of Manchester’s National Drug Evidence Centre. Rather than setting up treatments to be tested on patients allocated by researchers, the study simply tracked what happened after patients presented in the normal way to usual drug treatment services. For this reason it was unable to compare the effectiveness of one treatment with another (caseload differences could invalidate such a comparison), but was able to shed light on the progress typically achieved during and after typical treatments.
In each of 94 areas during a four- to seven-week window between February 2006 and March 2007, the study recruited and interviewed 1796 adults seeking treatment for primary drug (not alcohol) problems.
the_drug_treatment_outcomes_research_study.pdf