Public Release: 

Many drug control initiatives to date based on insufficient evidence

but emerging evidence-based interventions could reduce drug-related harms

Lancet

The pursuit of public good is an appropriate objective of drug policy, and necessitates the judicious application of controls over availability, prevention, treatments and rehabilitation. Public good may be achieved by increasing the number of people who are completely abstinent and also through reduced levels of use or changed patterns of use by those who continue to use. Policy makers have pursued many drug control initiatives that lack scientific evidence for their effectiveness, and that can cause harm through unintended consequences. But evidence-based interventions are emerging that can make drugs less available, reduce violence in drug markets, lessen misuse of legal (pharmaceutical) drugs, prevent initiation in young people, and reduce drug use and its consequences among existing users. The issues are discussed in the second paper in the Lancet Series on Addiction, written by Professor John Strang, National Addiction Centre, London, King's College London, UK, and colleagues.

The authors say: "Much public debate in drug policy is only minimally informed by scientific evidence. Values and political processes are important drivers of drug policy, but evidence of effectiveness and cost-effectiveness can help the public and policy makers to select policies that best achieve agreed goals."

Regarding drug supply, the evidence backs a number of conclusions, firstly that if law enforcement can keep prices high, drug initiation and use will be reduced. The very illegality of drugs makes them far more expensive than if they were legal, taxed, products. But keeping prices high can be hard, with one study in America showing that a 4.6 times increase in prisoners detained on drug-related offences only saw a 5% to 15% increase in the price of cocaine. There is no evidence that alternative development programmes (e.g. subsidies to grow different crops) in source countries have reduced drug use in final market countries at the other end of the drug distribution chain. But supply shocks can sometimes affect the drugs market and reduce use, purity, and harms related to drugs, as the examples of the Taliban opium ban, and 1989-90 war on Columbian Drug Traffickers, the restrictions on crystal meth precursors in the USA, and the Australian heroin shortage suggest. The authors add that wide-scale arrests and imprisonments have limited effectiveness, whereas drug testing of individuals under criminal justice supervision, accompanied by specific, immediate, and brief sentences (eg, overnight), have produced substantial reductions in drug use and offending.

Controlling prescription drugs is a different problem, and abuses are common and increasing, for example the steady rise in misuse of sustained-release opioid painkillers in the USA and Canada. Sourcing of prescription drugs occurs through different forms of diversion--eg, double doctoring (having two family doctors), prescription drug fraud, and thefts and robberies. Family and friends are also a primary source for individuals who use pharmaceuticals non-medically. Such sourcing patterns make the reduction of supply through traditional law enforcement difficult. The authors say: "Prescription monitoring systems can reduce irregular prescribing practices, but a balance is needed between the need for access to drugs for legitimate pain relief and the need to restrict access to deter inappropriate non-medicinal use."

Screening and brief intervention programmes have, on average, only small effects, but can be widely applied and are probably cost-effective. School, family, and community prevention programmes often have little impact, although even modest impact may be appraised differently by different stakeholders. The authors say: "Ideally, preventive interventions should stop young people from starting drug use, but they can also valuably delay initiation of drug use and prevent young people from becoming regular and dependent drug users."

"Treatment works" is an often-quoted mantra intended to alert health professionals and the public to the various benefits of addiction treatment. But this is not true of all types of treatment given to problem drug users. The treatment with the strongest research evidence of effectiveness is substitution treatment for addiction to heroin and other opioids. Evidence is much weaker for treatment of problem use of other drugs such as cocaine, crack cocaine, and methamphetamine (crystal meth). Oral opiate antagonists (naltrexone) are pharmacologically highly effective (and work with alcohol also) but benefit is marred by extremely poor adherence. Extremely long-acting implant or depot versions of several of these medications have been developed and are being trialled, as are novel vaccines against specific drugs; however, the future impact of these innovations is unclear.

Behavioural and psychosocial interventions, including residential rehabilitation, also have evidence supporting their effect. The effect size from contingency management (eg, voucher reinforcement of positive behaviours) is particularly notable. Opportunistic brief interventions for drug users with very low or no contact with treatment can increase help-seeking behaviour and stimulate change in behaviour.

The authors conclude: "Drug policy has the potential to contribute more to the public good by focusing on interventions with the largest potential population effect, the strongest evidence of effectiveness and cost-effectiveness, and the closest link between the outcomes of the policy and society's idea of the public good. Funders and researchers should pay greater attention to more policy-relevant areas in addiction research if society's ability to adopt a more evidence based approach to drug policy is to be improved."

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For Professor John Strang, National Addiction Centre, London, and King's College London, UK, please contact Russell Guthrie on 44-20-3228-2621 or 44-7930-943973 E) Russell.Guthrie@slam.nhs.uk / john.strang@kcl.ac.uk

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