Illicit drugs are drugs that have been prohibited under international drug control treaties.1 The main groups of illicit drugs used in international statistics are opioids, cocaine, amphetamines and cannabis. However, there is a range of other illicit drugs included in international drug control treaties, such as plant-based and synthetic hallucinogens. A full list of illicit drugs and classification can be found in the UNODC’s publication Terminology and Information on Drugs.2
Excess consumption or dependency can have a severe and detrimental impact on overall health, mental wellbeing and in many cases, the wellbeing of others. This entry provides a global overview of illicit drug use (extending from moderate to excess consumption), dependency disorders, and some of their consequential impacts.
Not all illicit drugs have similar impacts on health and wellbeing. The impact of some of them is very much lower than the harm caused by other illicit drugs.
- Illicit drug use is – directly and indirectly – responsible for over 750,000 deaths per year.
- Illicit drug use is responsible for 585,000 premature deaths by increasing the risk of particular disease and injury.
- Over 166,000 die from drug overdoses each year.
- More than half of those who die from drug overdoses are younger than 50 years old.
- Opioids are responsible for the largest number of overdoses from illicit drugs.
- It is estimated that around 1% of the world has a drug use disorder.
- The US had the highest overdose rates from all three leading illicit drugs: opioids, amphetamine and cocaine.
To understand the impact of illicit drugs on health and mortality it is important to understand the epidemiological terminology:
The Global Burden of Disease study identifies and provides estimates for drug use deaths through two pathways. The first is a direct death from a ‘drug use disorder’. A drug use disorder is characterized by meeting the criteria for dependence as defined by the World Health Organization’s International Classification of Diseases (ICD-10).3 Deaths from drug use disorders can be considered drug overdoses, with the terms being used interchangeably in the study literature.4
The second pathway is indirect: drug use can increase the risk of premature from a range of causes.5 These deaths are those premature deaths that occur because the use of illicit drugs increased the risk of diseases and injury, including suicide, liver disease, hepatitis, cancer and HIV.6
Related research entries
Substance use – Illicit drugs alongside alcohol and smoking are drugs with significant health impacts. In our meta-entry on substance use we look at the aggregate impacts of these drugs.
Alcohol consumption – Alcohol is a drug which has a big global health impact. How has alcohol consumption changed over time? How common is alcoholism, and what are the impacts?
Smoking – Tobacco use is not considered to be a substance use disorder – unlike illicit drugs and alcohol – but smoking does have a very large death toll in terms of indirect deaths from other diseases. How much do people smoke across the world? What are the health implications?
Support for substance use disorders
At the end of this entry you will find additional resources and guidance if you, or someone you know needs support in dealing with a substance use disorder.
Deaths from illicit drug use can be differentiated in two ways: as an indirect risk factor for premature death from disease or injury; and as a direct death from drug dependency and overdoses.
In the visualization we summarize the results of the Global Burden of Disease study on the number of deaths attributed to drug use: this is differentiated between indirect deaths as a risk factor (shown in blue) and direct deaths from drug overdoses (in red).
Globally, illicit drug use was responsible for just over 750,000 deaths in 2017. This is nearly double the number of deaths from homicide – 400,000.
This visualization shows the number of premature deaths from drug use.
This is an estimation of the number of people who died early because of the use of illicit drugs during their life. This is different from the estimates below which focus on the number of deaths directly caused by illicit drug use.
The premature deaths from illicit drug use as a risk factor encompass a wide range of causes of death for which the use of illicit drugs is a risk factor. These deaths are those premature deaths that occur because the use of illicit drugs increased the risk of diseases and injury, including suicide, liver disease, hepatitis, cancer and HIV.7
It is broken down by age – this is most clearly visible in the relative view. In 2017 42% of all who died were younger than 50 years.
This chart shows the number of direct deaths – those from drug use disorders – by age.
Overdoses of illicit drugs caused an estimated 167,000 deaths in 2017; 59% were younger than 50 years old.
The visualization shows the number of deaths from overdoses by specific drugs.
Here we see that opioids were responsible for the largest number of overdoses – 110,000 in 2017. The number of opioid deaths has been rising steeply over the past few years.
Using the “change country” toggle on the interactive chart you can explore this data by country and region. We see that the US in particular has seen a very steep rise in overdose deaths in recent years. In 2017, drug overdoses were the leading cause of death in adults under 50 years old in the US.
Drug use disorder, also known as drug dependence, is defined by the IHME based on the definition within the WHO’s International Classification of Diseases (ICD-10). It encapsulates the same dependency criteria and diagnosis as that of substance use disorders (described here), but is distinguished by the fact that it does not include alcohol use disorders. This means it is inclusive of all illicit drugs (whether prescribed or otherwise) including opioids, cocaine, amphetamine and cannabis. This classification does not include tobacco.
It’s estimated that globally around 0.9% of the population had a drug use (excluding alcohol) disorder in 2017. The trends in prevalence across the world are shown in the chart. At the country-level, this prevalence ranged from 0.4 to 3.5 percent. The highest prevalence was in the United States where around 1-in-30 had a drug use addiction in 2017.
When these trends are broken down by age, we see that globally, adults in their twenties are most likely to have a drug use disorder; more than 2 percent (1-in-50) people aged 20-29 do. In the United States, 8-9 percent of adults in their early twenties had a drug use disorder in 2017; this is around 1-in-11 or 1-in-12.
It’s estimated that globally around 71 million people had a drug use disorder in 2017.
Most of these have an addiction to opioids, it accounts for around 55 percent of drug use disorders globally. Cannabis addiction accounts for approximately one-quarter.
In the chart we see the difference in the share of men versus the share of women with a drug use disorder. In every country we see that men are more likely to have a drug addiction than women.
As was covered for total substance use deaths, the statistics here cover only direct death rates reported to occur from drug use disorders. It does not account for indirect (but sometimes connected) deaths from suicide.8
We discuss the evidence of this link between mental health, substance use and suicide in our entry on Mental Health. It’s estimated that an individual with opioid, or psychostimulant dependence has an increased risk of suicide of 7 and 8, respectively, relative to an individual without.
Globally it’s estimated that there were around 166,000 direct deaths from drug use disorders in 2017. The chart shows death rates across the world, measured as the number of direct deaths per 100,000 individuals in a given population. The United States had the highest death rate at almost 20 deaths per 100,000.
In recent years there has been a significant increase in overdose rates in the United States — particularly from opioids. In 2017, the US Department of Health and Human Services declared the opioid crisis a public emergency.
Overdose rates from various substances in the United States since the late 1990s are shown in the chart; these figures are based on official statistics from the US Centre for Disease Control and Prevention (CDC). Note that these figures — unlike IHME data used elsewhere in this entry – are not age-standardized.
Here we see that overdose rates from non-opiates (cocaine) have remained relatively constant over this period. Opioids – which include heroin, in addition to subscribed opioid pain relievers – show a steep rise; since the late 1990s, the rate of overdose has more than tripled.
Using the measure of deaths fails to capture the full extent of health consequences of drug use disorders. This is because drugs do not only cause deaths but can also lead to diseases and disabilities. In this charts we present data on the attributed ‘disease burden‘ of drug use disorders. The disease burden is measured in Disability-Adjusted Life Years (DALYs). This metric considers not only death rates, but also years lived with disease and disability.
As shown in the chart, the United States has the highest rate of disease burden (as measured by DALYs per 100,000 individuals). Disease burden trends differentiated by age can be found here.
The map here shows the death rate from opioid overdoses across the world.
Opioid overdoses were by far the most common in the United States, at 13.3 deaths per 100,000. This was twice as high as the second country – Libya – at 7 deaths per 100,000. And the US rate is up to 40-times higher than in some countries in Europe (like Italy, Poland or Hungary).
By clicking on a given country you can see how opioid overdose rates have changed over time. For the US in particular we see a rapid rise; over the past decade rates have more than tripled.
In this map we see the death rate from amphetamine overdoses across the world.
Just as with opioids, the US has the highest rates of amphetamine overdoses. In 2017, its rates were double that of the next highest countries – Sweden and Finland.
This map shows death rate from cocaine overdoses across the world.
Consistent with other drug overdoses, the US had the highest overdose rates from cocaine.
As we discuss in our entry on Mental Health, the risk factors and contributors to the onset and persistent of Mental and Substance Use disorders are often complex with interplay between genetic, personality trait, environmental conditions and life events. Although they should in many cases be treated differently, the range of risk factors – from preconception through to old age – described in our Mental Health entry are likely to also apply in cases of Substance Use disorder.
It is important to acknowledge that the risk factors uptake and addiction to a particular substance can vary across the stages of this process. In Kreek et al. (2005) the authors propose the relative contribution of different factors to drug initiation, regular use and addiction or relapse, in Nature Neuroscience.9
The authors suggest that the initiation of drug use is often most closely associated with impulsivity and risk-taking tendencies (which typically have a genetic component), in addition to particular environment factors. The transition from initiation to intermittent or regular use is based on the interplay of many factors including impulsivity, risk-taking tendencies, stress response and comorbidity in addition to environmental factors. Finally the transition from intermittent or regular use towards addiction and relapse are most strongly influenced by a mixture of stress response, environmental factors, genetic predisposition to addiction and importantly the drug-induced effects which often create a cycle of addiction and relapse.
A number of studies have found impulsivity and risk-taking traits to be a leading vulnerability factor in the development of a substance use disorder.10
Such characteristics are also often seen in individuals with Attention Deficit Hyperactivity Disorder (ADHD). A number of studies have found a strong link between individuals with ADHD and increased risk of the onset of a substance use disorder.11,12,13
The impulsivity trait of ADHD in particular is identified as an important vulnerability for later onset of substance use disorders.14
This does not infer that all individuals with ADHD will later develop a substance use disorder; however, studies suggest that there is an increased likelihood in individuals with ADHD relative to those without (as discussed below).
It is known that mental health and substance disorders can be closely related: the IHME often group these disorders together in a collective category when discussing related statistics. However, there is also significant evidence that individual mental health disorders, although to varying degrees, can increase the likelihood of an individual developing a substance use disorder relative to those without.
In the chart we show results from a study conducted published by Swendsen et al. (2010).15
In this study the authors followed a cohort of more than 5000 individuals, with and without a mental health disorder (but without a substance use disorder) over a 10-year period. Following the 10 year period they re-assessed such individuals for whether they had either a nicotine, alcohol or illicit drug dependency.16
The results in the chart show the increased risk of developing an illicit drug use disorder (alcohol dependency results are shown in our entry on Alcohol Consumption) for someone with a given mental health disorder (relative to those without). For example, a value of 5.2 for attention deficit hyperactivity disorder (ADHD) indicates an individual with ADHD would be more than 5 times as likely to develop an illicit drug dependency relative to someone without. The risk of a substance use disorder is highest in individuals with Intermittent explosive disorder, ADHD, and bipolar disorder.
There is often the perception that substance use is more common in young people. But does the data support this assumption?
In the chart we see the prevalence of drug use disorders differentiated by age group, given as the percentage of people within that age bracket with a drug use dependency.
Here the USA is shown, but this data can be found for any country using the “change country” button on the chart.
Overall, we tend to find that the prevalence of drug use disorders is highest in people in their twenties. For example, in the USA, 9 percent of those aged 20-24 years old had a drug use disorder in 2017; this is three-times higher than the total population average of 3 percent. The higher prevalence of substance use disorders in people in their twenties (or sometimes in their late teens) is consistent across most countries.
Is this finding a reflection of today’s young generation, or has this been a historically consistent trend with age? In other words: is the prevalence in today’s young cohort uncharacteristically high, or is it a persistent pattern that drug use increases through peoples’ late teens and early twenties before declining thereafter? It appears to be the latter. The finding that drug use disorders tend to be most common in people in their early twenties has been consistently reported for decades: studies dating back to the 1980s and 1990s attempt to explain why substance use tends to peak during this period.17,18
There are a number of related behavioural and social factors which may partly explain why this peaks in the early twenties. Initiation of alcohol or drug use tends to begin in the late teenage years, after which the following years represent a key period of self-identity, exploration and higher affinity for risk-taking.19,20
Such attributes, combined with social pressures and the aspiration to fit in with peers can lead to more frequent substance use and the potential to develop a drug dependency.
Beyond the early twenties, the prevalence can often decline through means of selection and self-correction. A longitudinal study of young adults in the 1990s found that the impact of common aspirations such as marriage, parenthood and steady employment tend to result in a decline in substance use.21
The study suggests that by ages 28-31, individuals who were married and/or had children had much lower use of alcohol, cigarettes and illicit drugs (and lower perception of substance use in friends) than those without.
Substance use disorder, also known as substance dependence, is defined by the IHME based on the definition within the WHO’s International Classification of Diseases (ICD-10).22 Substance use disorders include alcohol and all illicit drugs (whether prescribed or otherwise) including opioids, cocaine, amphetamine and cannabis.
The IHME classification does not include tobacco – the health burden as a result of tobacco smoking is discussed in our entry on smoking.
A definite diagnosis of dependence should usually be made only if three or more of the following have been present together at some time during the previous year:
- (a) a strong desire or sense of compulsion to take the substance;
- (b) difficulties in controlling substance-taking behaviour in terms of its onset, termination, or levels of use;
- (c) a physiological withdrawal state when substance use has ceased or been reduced, as evidenced by: the characteristic withdrawal syndrome for the substance; or use of the same (or a closely related) substance with the intention of relieving or avoiding withdrawal symptoms;
- (d) evidence of tolerance, such that increased doses of the psychoactive substance are required in order to achieve effects originally produced by lower doses (clear examples of this are found in alcohol- and opiate-dependent individuals who may take daily doses sufficient to incapacitate or kill nontolerant users);
- (e) progressive neglect of alternative pleasures or interests because of psychoactive substance use, increased amount of time necessary to obtain or take the substance or to recover from its effects;
- (f) persisting with substance use despite clear evidence of overtly harmful consequences, such as harm to the liver through excessive drinking, depressive mood states consequent to periods of heavy substance use, or drug-related impairment of cognitive functioning; efforts should be made to determine that the user was actually, or could be expected to be, aware of the nature and extent of the harm.
Illicit drugs include plant-based drugs – such as cocaine and cannabis; synthetic drugs – such as amphetamines; and pharmaceutical drugs – such as heroin and other opioids and benzodiazepines.
The majority of data presented in this entry is based on estimates from the IHME’s Global Burden of Disease (GBD). This is currently one of the only sources which produces global level estimates across most countries on the prevalence and disease burden of mental health and substance use disorders.
Nonetheless, the GBD acknowledges the clear data gaps which exist on mental health prevalence across the world. Despite being the 5th largest disease burden at a global level (and with within the top three across many countries), detailed data is often lacking. This is particularly true of lower-income countries. The Global Burden of Disease note that the range of epidemiological studies they draw upon for global and national estimates are unequally distributed across disorders, age groups, countries and epidemiological parameters.23
Utilising these studies to provide full coverage of these disorders is challenging.
To overcome these methodological challenges the authors note:
To deal with this issue and be able to include data derived using various study methodologies and designs, GBD 2013 makes use of DisMod-MR, version 2.0, a Bayesian meta-regression tool. The software makes it possible to pool all of the epidemiological data available for a given disorder into a weighted average, while simultaneously adjusting for known sources of variability in estimates reported across studies. If raw data are not available for a given country, the software produces an imputed estimate for each epidemiological parameter based on data available from surrounding countries. This allowed GBD to include estimates for 188 countries.
Institute of Health Metrics and Evaluation (IHME), Global Burden of Disease (GBD)
- Data: Deaths, DALYs and prevalence of mental health and substance use disorders, by age and sex
- Geographical coverage: Global by country and region
- Time span: from 1990 onwards
- Available at: http://ghdx.healthdata.org/gbd-results-tool
World Health Organization (WHO) International Classification of Diseases (ICD)
World Health Organization. (1992). The ICD-10 classification of mental and behavioural disorders: clinical descriptions and diagnostic guidelines (Vol. 1). World Health Organization.
- Data: Definitions and classifications of mental and substance use disorders
- Available at: ICD-10 Classification of Mental and Behavioural Disorders
World Health Organization (WHO) Global Health Observatory (GHO)
- Data: Prevalence of substance use disorders, trends in alcohol consumption
- Geographical coverage: Global by country
- Time span: Variable depending on datasets. Most inconsistent years post-2000
- Available at: http://www.who.int/gho/en/
National Institute on Drug Abuse (NIDA)
- Information: Guidance and support on treatment. Specific guides for teens, young adults and adults, as well as those trying to support someone with a drug use disorder.
- Geographical coverage: Universal guidance; US-based treatment
- Available at: https://www.drugabuse.gov/related-topics/treatment
UK National Health Service (NHS) Guidance
- Information: Guidance and support on where to get help with a drug use disorder
- Geographical coverage: UK only
- Available at: https://www.nhs.uk/livewell/drugs/pages/drugtreatment.aspx
- Information: Free, confidential support services online, and by phone. General information ranging from drug effects to support for a drug dependency.
- Geographical coverage: Global
- Available at: http://www.talktofrank.com/
WHO Guidelines for the identification and management of substance use and substance use disorders in pregnancy
- Information: Guidance from the World Health Organization (WHO) for healthcare providers managing women from conception to birth and the postnatal period, and their infants.
- Geographical coverage: Global
- Available at: WHO Guidance