The Lancet Series on Drug Use

December 2019
The Lancet Series on Drug Use was recently published and launched at a special session at the Lisbon Addictions Conference 2019.

Led by NDARC authors, The Lancet Series on Drug Use focuses on opioids, cannabinoids, stimulants, and new psychoactive substances (NPS). We review the evidence on the epidemiology of drug use and related harms and interventions (treatment and policies) to address them. And we highlight issues that are likely to become increasingly important in the next decade.

Why we produced The Lancet Series on Drug Use

20th-century ways of thinking about and responding to drugs are no longer fit for purpose. The 2016 UN General Assembly Special Session on Drugs underlined the need for policies that respond to new challenges of drug use. The UN Sustainable Development Goals (SDGs) include scaling up effective drug treatment and prevention; the social equity SDGs will also be fundamental to prevention of drug-related harm.

All stakeholders must base policies and actions more on science and less on moral judgments to meet the growing challenges that drug use poses to future global health.

About the Drug Use Series

The Lancet Series on Drug Use reviewed evidence for interventions to address drug-related harms; some interventions are more effective than others in the magnitude and range of impacts.

Despite their superiority, these effective interventions go underfunded, whereas other ineffective interventions that are well intentioned or shaped by moral judgments about drug use are strongly supported.

Professional and public policy discourse needs to adapt to these new realities. The use of opioids, cannabinoids, stimulants, NPS, alcohol, and tobacco and the non-therapeutic use of medicines often overlap, but interventions typically focus on single drugs. Legal and illegal substance use, alongside economic austerity, contribute to causes of deaths and decline in life expectancy in several countries. Drug use policies need to address drug use more holistically, and recognise the contribution of economic distress and social factors to drug use and harms. Factors that influence patterns of drug use over an individual's life course are not fully understood, and more research is needed on how families, peers, and environment support recovery or minimise progression to harmful use and dependence.


Opioid dependence causes the greatest disease burden of all extramedical drug use.

The prescription of long-term opioid agonist treatment (OAT) is an essential component of an effective public health response to opioid dependence. These medicines have shown positive impacts across multiple health and social domains, including reduction of opioid use, overdose, and incidence of HIV and hepatitis C virus (HCV) infection.

The Series shows that access to and retention on OAT both in the community and in prisons substantially reduce opioid-related premature mortality. Other strategies, such as use of naloxone by families, peers, and first responders, underscore the importance of community responses in reducing opioid-related harms.


A stronger evidence base and greater policy support are needed to improve responses to the needs of people dependent on stimulants. Effective psychosocial interventions such as contingency management are not sufficiently available. Currently, there are no effective medicines for stimulant dependence, although there are effective approaches to reduce harms related to use of stimulants.

New Psychoactive Substances (NPS)

Hundreds of new psychoactive substances (NPS) have emerged in the past two decades, some of which have been placed under control by national and international laws.

Expressions of global concern about “drugs” elide important differences between them. NPS, for example, aggregates substances that share little beyond their newness. New compounds can produce outbreaks of fatal poisonings and disappear from the market before rigorous scientific assessment is possible.

Toxicology data and consumers' reports are needed to identify those NPS most associated with physical or mental health problems, to inform better intervention and risk communication.


The legalisation of commercial cannabis production for medicinal and recreational use in the Americas could transform global cannabis markets. Cannabis legislation is still at an early stage so there is considerable uncertainty regarding the extent to which cannabis use and harm might increase. It will depend, in part, on how the legal market is regulated and taxed. It will also crucially depend on whether a legal cannabis market is regulated in ways that increase or decrease harms caused by cannabis, alcohol, opioids, and other drugs. By the time we can confidently answer these questions, legalisation might have made cannabis the fourth major legal recreational drug after caffeine, alcohol, and tobacco.

Criminal Justice System

The long-term detention of people who use drugs in compulsory drug detention centres has no short-term or long-term benefits, is cost-ineffective, and often involves unethical and inhumane practices such as forced labour, abuse, violence, and denial of medical treatment.

Punitive policy responses can amplify the health and social costs of drug use; evidence also suggests punishment is not necessarily an effective deterrent to offending.

UN agencies have invoked the principle of proportionality to call for reduction of prison sentences and overcrowding, and the decriminalisation of drug use and drug possession for personal use;

UN member states have similarly signed up to the Bangkok Rules and the Tokyo Rules, which state that prison should be considered a measure of last resort and must also focus on the needs of female prisoners. In some countries, courts provide pathways to treatment and rehabilitation as an alternative to incarceration.

Nonetheless, drug policy responses often include imprisonment to deter use, generating considerable economic costs, arguably to the detriment of funding effective treatment and harm reduction responses in the community.

There is a need for increased research and advocacy on the provision of health interventions to people in the criminal justice system. In many parts of the world, people detained for drug (or other) offences do not have access to HIV or HCV treatment, and have limited access to treatment for other drug-related health conditions. Provision of OAT in prisons would reduce interruptions in OAT receipt, could substantially reduce premature mortality, would improve multiple health outcomes during incarceration, and would enhance access to health services on release.

The development and application of long-acting buprenorphine could assist in the scale-up of treatment in prison.


Abstinence from drug use is not necessarily a precondition for public health benefit or positive change. For example, needle and syringe programmes that provide sterile injecting equipment for people who inject drugs reduce the risk of acquiring HIV and HCV.

HIV treatment in people who inject drugs reduces future HIV transmission; and HCV treatment in people who inject drugs both cures and averts further infections.

New interventions are being developed that offer promise. For example, biotechnological approaches to treatment include long-acting formulations of naltrexone and buprenorphine for opioid dependence and soon for antiretroviral treatments. These formulations reduce the need for daily clinic visits and supervised dosing, which many patients find impractical or undesirable. However, long-acting formulations have the potential for use under coercion and their introduction could be driven by the objective of preventing medication diversion rather than concerns over patient welfare and convenience. In introducing such approaches, health professionals and policy makers therefore need to listen to what people who use drugs say about what therapies are desirable and how best they can be delivered.

Meaningful community engagement and consultation is an essential element of effective prevention, treatment, and harm reduction. The voices and experiences of people who use drugs are crucial. Stigma and discrimination deter health-care access for those who use drugs and reduce treatment entry and retention.


The debate on drug policy typically focuses on legalisation and is too often polarised. Policy makers need to explore the continuum of policy options, including radical changes when the evidence indicates that these could produce substantial public health benefit. A genuine public health approach to drug use would focus less on the legal status of a particular drug and more on the harms and benefits of all psychoactive substance use, including tobacco, alcohol, and pharmaceutical drugs. Countries contemplating cannabis regulation should heed lessons from alcohol and tobacco policies to avoid a form of commercialisation that advances corporate interests over public health and promotes damaging patterns of cannabis use.

Demographic and social changes mean that the future health costs of drug use are increasingly likely to be borne by low-income and middle-income countries (LMICs). International and scientific dialogue can allow countries to benefit from evidence on effectiveness and avoid policy mistakes made by high-income countries, while recognising that responses effective in one cultural context may need cultural adaption in another. More data are needed from LMICs and on the interplay between drug use and economic and sociopolitical factors to better inform policy.

Finally, a stronger policy case needs to be made for investment in effective prevention and treatment initiatives. Credible estimates of the budgetary and public health impacts of different approaches are needed, including those which are ineffective. We need to ascertain the cost-effectiveness of different interventions and intervention combinations for the optimum allocation of scarce resources and health equality.

Read more:

The Lancet Series on Drug Use is available on The Lancet website.