- Report authors warn that the effects of cannabis legalisation will probably not be seen for another decade, problems resulting from stimulants are growing globally, and current responses to emerging substances may no longer be fit for purpose with rapid changes in drug supply and demand.
- To meet the growing challenges that drug use poses to future global health, policies and actions must be based on science, and not on moral judgements.
- Authors call for increased research funding to improve treatments, and for global policymakers to implement only evidence-based policies and therapies - they estimate that increased provision of opioid agonist treatment could help avoid around 8-26% of opioid-related deaths, compared to no treatment.
A report from The Lancet calls for a new international approach to drug use - using evidence-based policies, which adapt faster, and respond more humanely and effectively to new drugs and their changing availability and patterns of use.
The five-paper Series publishes as the opioid crisis continues, cannabis legalisation expands, global stimulant problems grow, and the number of new psychoactive substances (NPS) identified continues to increase. It reviews the global evidence on these four drug types - analysing patterns of use, related harms, and interventions, and estimating the benefits of opioid agonist therapy and the growing health impact of stimulant use. The report will also be presented at the Lisbon Addictions meeting in Lisbon, Portugal on 24 October.
"Globalisation and developments in information technology have transformed drug availability and use, and professional and public policy discourse need to adapt to these new challenges," says one of the authors of the report, Professor Louisa Degenhardt, National Drug and Alcohol Research Centre, UNSW Sydney, Australia. "Meaningful engagement with people who use drugs is essential to effective prevention, treatment, and harm reduction. Underlying the negative attitudes faced by people who use drugs are moral judgments that people who use drugs are undeserving of humane treatment and that their human rights can be justifiably violated. Confronting these false claims is a social and moral imperative." 
In a linked Comment, The Lancet editors, Dr Pam Das, Senior Executive Editor, and Dr Richard Horton, Editor-in-Chief, say that the authors highlight issues that are likely to become increasingly important in the next decade. They note: "It is time to recognise the humanity of people who use drugs, and to offer them similar solidarity and protection from the worst excesses of populist politics. The medical community must stand up for the rights of people with drug use disorders to receive evidence-based care that respects their rights, minimises harm, and provides a stable, non-judgmental basis from which they can effect positive change in their lives."
Existing estimates have suggested that in 2017 about 271 million people aged 15-64 years (5.5% of the population) had used drugs in the previous year, and between 35-72 million people had drug use disorders globally.
Creating effective treatments for growing issues
The growing problems arising from cocaine and amphetamine use present major challenges to health and justice services in many parts of the world. The authors report that globally, around four in 1,000 people used cocaine and seven in 1,000 used amphetamines in 2018, with an estimated 16% and 11% of these people experiencing dependence, respectively.
People who use stimulants have a mortality rate six times higher than people who do not use stimulants, this being from elevated risk of suicide, injuries, cardiovascular disease, and homicide (equivalent to an estimated 178,000 and 326,000 deaths associated with cocaine and amphetamine dependence, respectively, in 2017) . The authors also link stimulant use to poor mental health, violence, injury, sexually transmitted infections and blood borne virus risk, and foetal harm. They estimate that, on average, every 10% increase in people injecting stimulants could account for an additional 5-10% of new HIV infections and 3-7% of new hepatitis C infections per year.
The authors call on funders to focus investments on this underserved area, noting that there are few effective treatments for stimulant dependence, except for contingency management. Report co-author Professor Michael Farrell, National Drug and Alcohol Research Centre, UNSW Sydney, Australia, says: "Insufficient long-term investment for research and application of evidence-based treatments for stimulant dependence has led governments to rely on law enforcement. Globally, and particularly in the Asia-Pacific region, policy has been dominated by incarceration, with an estimated 235,000 people detained in compulsory drug detention centres in which major infringements of human rights occur. Instead, problems with stimulants require sustained, comprehensive strategies to reduce long-term use and dependence, and substantial research investment is needed to develop these." 
Responding to emerging issues
Further research is also needed to address emerging drug trends, including the expansion of cannabis legalisation, and the rapid emergence of a range of new psychoactive substances (NPS - a broad group of psychoactive synthetic substances previously known as legal highs, including stimulants like mephedrone, synthetic cannabinoids like Spice, and synthetic opioids like carfentanil).
NPS challenge traditional approaches to drug monitoring, control and public health responses as they comprise a large variety of substances (each with different risk profiles and potencies), which quickly enter and exit the market, with frequent misinformation around their content. By the end of 2018, the United Nations Office on Drugs and Crime had received reports of 892 different NPS. While data from high-income countries suggest that NPS form a smaller proportion of the total drug market relative to more established illicit drugs, low- and middle-income countries often do not have the surveillance abilities to identify these drugs, meaning they may go unseen.
Report author Dr Amy Peacock, National Drug and Alcohol Research Centre, UNSW Sydney, Australia, says: "The current and future effects of NPS in low- and middle-income countries are less clear than in high-income countries, but, in many ways, more worrying. These substances could shape emerging drug markets in countries with large youth populations that are undergoing rapid social changes and experiencing problems with governance, poverty, and social marginalisation. In a world in which different substances can be rapidly introduced, and where people who use drugs change preferences depending on availability amongst other factors, the current means of responding to emerging substances might no longer be fit for purpose, and will need greater international collaboration to tackle. We must focus less on the legal status of new substances, and instead concentrate on improving prevention, treatment, and harm reduction." 
The authors outline research priorities for understanding the effects of cannabis legalisation (panel 2, paper 2), and note that it will take until the market matures - in at least a decade - to establish the full impact. They point out that measuring trends in use, associated harms, potency, and social norms around safe use will be crucial, as will improving treatment of cannabis dependence, and understanding how use of cannabis affects alcohol, tobacco, and opioid use.
Applying evidence-based policies and treatment
In the meantime, the authors say that cannabis legalisation in the USA, Canada, and Uruguay is likely to influence global policy in the long term - with Colombia, Luxembourg, Mexico, the Netherlands, New Zealand, and Switzerland considering legalisation currently. They stress that governments should adopt evidence-based policies to mitigate harm when legalising cannabis, such as those shown to mitigate alcohol- and tobacco-related harm (for example, using taxes to discourage heavy use, restricting advertising, limiting the number of outlets to buy cannabis, and treating dependence).
Effective interventions must also be applied to the opioid crisis, where treatment quality is insufficient despite the scale of the issue - only 86 of 179 countries with injecting drug use offer opioid agonist treatment (the most effective treatment for opioid dependence, which reduces harms across multiple health outcomes), and only 20 of those have sufficient access. They suggest that the US opioid crisis is based on two failures: one in early identification and control of over-prescription and mismarketing of medical opioids, and the other in later not providing enough evidence-based treatment and harm reduction measures in the community.
The authors estimate that expanding methadone or buprenorphine opioid agonist treatment in the community to 40% of people who are opioid dependent followed by improving prison access to OAT and improving the average duration of treatment to 2 years in Kentucky (USA), Kiev (Ukraine), and Tehran (Iran) could avert 8-26% of all opioid-related deaths, compared to no treatment between 2020-2040. This includes 34-57% fewer deaths from overdose and 25-56% fewer HIV deaths .
"Despite their superiority, these effective interventions go underfunded, while other ineffective interventions that are well intentioned or shaped by moral judgements are strongly supported. Opioid dependence is the third most important substance use disorder (after tobacco and alcohol) in terms of contribution to premature deaths and disease, yet the coverage of interventions to prevention of opioid-related harms to health is woefully inadequate in most countries. It is imperative that we expand opioid agonist treatment availability to improve the quality of treatment to people who are dependent on opioids worldwide," says Professor Degenhardt. 
She concludes: "In the face of growing and evolving drug challenges, we must turn our backs on old ways of thinking and encourage new humane approaches - championing this new approach to encourage change worldwide. We must invest funds to develop treatments for drug use as a chronic disease, apply the evidence-based policies and treatments we have available, and adopt approaches based on public health and human rights." 
NOTES TO EDITORS
This Series was funded by Australian National Health and Medical Research Council, Australian Government Department of Health, Australian National Drug and Alcohol Research Centre (NDARC), UNSW Sydney, and the European Monitoring Centre on Drugs and Drug Addiction.
 Quote direct from author and cannot be found in the text of the Article.
 In 2017, cocaine dependence was associated with an estimated 0.65% of suicide deaths, 0.24% of accidental injury deaths, 0.14% of cardiovascular deaths, and 0.47% of homicide deaths.
In 2017, amphetamine dependence was associated with an estimated 1.23% of suicide deaths, 0.59% of accidental injury deaths, 0.48% of cardiovascular deaths, and 1.23% of homicide deaths.
 Further findings from the modelling available in Figure 3 of paper 1. Key findings:
If opioid agonist treatment (OAT) coverage is scaled up to 40% in the community only, 2-13% of all deaths in people who inject drugs and people who previously injected drugs (including 18-44% of overdose deaths) could be avoided between 2020-2040.
These reductions are estimated to almost double if OAT treatment duration were also increased to two years (4-17% deaths avoided), and would triple if OAT was provided to people in prisons and on release from prison (8-26% deaths avoided).
Increasing OAT coverage, improving retention, and providing OAT in prisons could prevent 57% of all deaths caused by overdose among people who inject drugs in Kentucky, and 56% of HIV-related deaths among people who inject drugs and people who previously injected drugs in Tehran.
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