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Around 200 million people using illicit drugs worldwide each year, with use highest in high-income countries

Drug-related burden of disease appears similar to that caused by alcohol in these developed countries


The first paper in the Lancet Series on Addiction addresses the global burden of disease due to illicit drug use, and reports estimates that some 200 million people (range 149-271 million) worldwide use illicit drugs each year. This figure represents 1 in 20 people aged 15-64 years, and use is highest in developed countries. Furthermore, the burden of disease due to drug use in high-income countries such as Australia is a sizeable proportion of that caused by alcohol consumption, but much less than that caused by tobacco. The paper is by Professor Louisa Degenhardt, National Drug and Alcohol Research Centre, University of New South Wales, Sydney, and the Burnet Institute, Melbourne, Australia; and Professor Wayne Hall, University of Queensland Centre for Clinical Research, Brisbane, Australia.

The illegality of opioids, amphetamines, cocaine, and cannabis precludes the accurate estimation of how many people use these drugs, how many people are problem users (including people who are dependent), and what harms their use causes. The authors note that this is a major unintended consequence of the prohibition of such drug use. They also note that due to limitations in the data on extent of use, and the nature of related harms, the burden attributable to MDMA (ecstasy), hallucinogenic drugs, inhalants, or non-medical use of benzodiazepines (such as valium) or anabolic steroids has never been estimated. Available data suggest that, in the total illicit drug users mentioned above there are 125-203 million cannabis users, 14-56 million amphetamine users, 14-21 million cocaine users and 12-21 million opioid users. There are an estimated 15-39 million problematic users of opioids, amphetamines, or cocaine, and 11-21 million people who inject drugs.

According to estimates made by the UN Office on Drugs and Crime, cannabis use appears to be highest in Oceania (Australia/New Zealand) with up to 15% of 15-64 year olds using the drug, while opioid use including heroin was highest in the Near and Middle East (up to 1.4%). For amphetamines, again Oceania came out highest with up to 2.8% of this age group using drugs such as speed and crystal meth (but not including ecstasy), and cocaine use was highest in North America (1.9%).

The authors highlight that no gold-standard method exists for the estimation of the true size of the population of illicit drug users, and that no one method is ideal for all drugs or all countries.

Four broad types of adverse health effects of illicit drug use exist: the acute toxic effects, including overdose; the acute effects of intoxication, such as accidental injury and violence; development of dependence; and adverse health effects of sustained chronic, regular use, such as physical diseases. The authors highlight that cannabis causes very few deaths (no overdoses or blood-borne virus infections) though it may cause some accidental deaths. However it clearly causes many users to become dependent and probably contributes to mental disorders. Opioids have been shown to have all four types of health effects: they have the highest risks of dependence affecting perhaps 1 in 4 of lifetime users, and are major contributors to premature death due to overdoses, often in combination with other drugs, as well as accidents, suicides and violence, HIV/AIDS and hepatitis. They are also major contributors to disability, through dependence, chronic infections, and liver disease.

The most recent data reported by the World Health Organization (2004) suggest that 250,000 deaths worldwide were due to illicit drug use, compared with 2.25 million due to alcohol and 5.1 million due to tobacco. Years of life lost due to drug use (2.1 million) were more than those recorded for alcohol (1.5 million), because drug deaths generally affect younger people, while alcohol deaths (and tobacco deaths) tend to affect middle-aged and elderly people. Furthermore, alcohol can have a protective effect when used in moderation in middle age. However, when years lost due to disability (DALYS) are considered, illicit drugs cause 13 million DALYS (0.9 of global DALYS), some 20% of those caused by alcohol (69 million/4.5% of global DALYS ) and 23% of those caused by tobacco (57 million/3.7% of global DALYS). The burden due to drugs does not, however, include adverse social effects on drug users, such as stigma and discrimination, or the adverse effects that drug-related behaviour has on communities, such as drug dealing, discarded injection equipment, endangerment of public safety, violence between drug dealers, and property crime. The authors add that on the basis of available evidence, most of the disease burden attributable to illicit drugs is concentrated in problem or dependent drug users, especially people who inject drugs.

However, the above figures are the overall global picture. In a high-income country such as Australia, illicit drugs are responsible for 2.0% of DALYS, compared with 2.3% for alcohol and 7.8% for tobacco. Opioids cause 80% of the drug DALY burden in Australia. Illicit drugs caused 1.3% of all deaths in Australia, compared to 0.8% for alcohol and 11.7% for tobacco. This was based on the assumption that moderate alcohol use reduced cardiovascular heart disease mortality in middle-aged adults. Patterns of drug-related DALYS distribution are likely to be similar in the USA and UK*. In terms of trends of drug use in Australia, cannabis is the most widely used drug although recreational use of this drug appears to be declining (with less marked changes in problematic cannabis use). Amphetamine use is more common than cocaine use, but cocaine, although comparatively very expensive in Australia, is rising in popularity. Use of opioids is much less common than it was in the late 1990s.

The authors conclude: "Intelligent policy responses to drug problems need better data for the prevalence of different types of illicit drug use and the harms that their use causes globally. This need is especially urgent in high-income countries with substantial rates of illicit drug use and in low-income and middle-income countries close to illicit drug production areas."


Professor Louisa Degenhardt, National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia. T) 61-403-373-878 / 61-459-835-192 E)

Marion Downey, Communications and Media Manager, National Drug and Alcohol Research Centre. T) 61-2-9385-0180 E)

Professor Wayne Hall, University of Queensland Centre for Clinical Research, Brisbane, Queensland, Australia. E)

Note to editors: *based on the World Mental Health Survey results that the picture is likely to be similar in the UK and USA and other high-income countries

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