This paper reviews what has been learned from the following major national drug treatment outcome studies: NTORS (National Treatment Outcome Research Study); DARP (the Drag Abuse Reporting Programme); TOPS (Treatment Outcome Prospective Study) and DATOS (Drug Abuse Treatment Outcome Study).

Key findings:
Substantial reductions in illegal drug misuse and other outcomes were found after treatment. Improved outcomes were also found for injecting risk behaviours.

Most drug dependent clients were multiple substance misusers and often had multiple dependencies. To focus on single substance disorders is outdated and misleading.

Overdose remained a serious problem among drug misusers with a greatly increased risk of mortality. Time in treatment and treatment completion were found to be associated with better treatment outcomes. Treatment effectiveness may be increased through improved rates of patient retention.

The reductions in crime levels provide substantial and immediate cost savings for society. Methadone programmes achieved a range of improved client outcomes. Case-mix differences were found, with more severely problematic drug misusers receiving treatment in residential programmes.

Most drug dependent clients received more than one episode of treatment. Little is known about possible cumulative effects of multiple treatments, or how separate and/or different treatment episodes interact or interfere with each other.

Drinking outcomes were often poor with many clients continuing to drink heavily. Treatment of drinking problems among drug misusers should be strengthened.