Efforts to reduce the demand for illicit drugs through school-based and mass education campaigns have been generally disappointing. In contrast, there is good evidence that reducing the demand for illicit drugs through drug dependence treatment can be effective at the individual and also the community level. The best evidence is for the treatment of heroin dependence using substitution drugs (methadone, buprenorphine or prescription heroin) in structured settings together with some psychosocial assistance. These treatments are effective, safe and cost effective. Benefits of methadone and buprenorphine treatment include a reduction in deaths, HIV infection, crime and drug use with improvements also seen in physical and mental health and social functioning. Methadone and buprenorphine treatment are more effective in attracting and retaining heroin dependent people than any other forms of treatment. Others forms of treatment are less well supported by evidence but are worth providing as methadone and buprenorphine treatment does not attract all heroin dependent people and does not benefit all who are attracted.

Psychosocial treatments for stimulant users (amphetamine, cocaine) are less well established but are worthwhile. There is some evidence that dexamphetamine substitution treatment benefits people dependent on amphetamine but the evidence is not as impressive as the evidence supporting methadone or buprenorphine treatment. No effective specific treatment has been found for cocaine users of people dependent on cannabis but supportive treatments are probably beneficial.

Drug treatment is often poorly funded and only able to cope with a small proportion of drug dependent people in a community. Many drug dependent people improve without assistance from clinicians.

Harm reduction, that is attempting to reduce harms directly without necessarily reducing consumption, is a very valuable part of the response to all psychoactive drugs including illegal drugs. Needle syringe programmes and methadone treatment are the best known examples. Both are effective, not accompanied by significant unintended negative consequences and bth are cost-effective. Harm reduction has helped to reduce the spread of HIV among people who inject drugs and from them to the general population.