Aims Treatment of drug addiction has been the subject of substantial research and, in contrast to several other methods of reducing drug use, has been found to be both effective and cost-effective. This review considers what is known about how much a nation can reduce its drug problems through treatment alone and what is known at the aggregate level about the effectiveness of prevention and enforcement.
Methods The literature on the effectiveness of treatment, prevention and enforcement are reviewed, and set in a policy analytical framework.
Findings Many studies have found treatment to have large effects on individuals’ consumption and harms. However, there is an absence of evidence that even relatively well-funded treatment systems have much reduced the number of people in a nation who engage in problematic drug use. For prevention, the scientific literature shows useful and modest effects at the individual level but there is little support for substantial aggregate effects. For enforcement, research has failed almost uniformly to show that intensified policing or sanctions have reduced either drug prevalence or drug-related harm. Nor—outside the UK—is there more than a modest effort to improve the evidence base for making decisions about the appropriate level of enforcement of drug prohibitions.
Conclusions Treatment can justify itself in terms of reductions in harms to individuals and communities. However, even treatment systems that offer generous access to good quality services will leave a nation with substantial drug problem. Finding effective complementary programs remains a major challenge.