Drug Use

This article was first published in April 2018.

Substance use is broad in its definition, being inclusive of alcohol and other drugs. Whilst moderate consumption of some can be a cultural or social norm (alcohol, for example), 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 substance use (extending from moderate to excess consumption), substance use or dependency disorders, and some of their consequential impacts.

This overview focuses on illicit drug use disorders as classified by the Institute of Health Metrics and Evaluation (IHME) and World Health Organization (WHO).

Related entries:

  • Full data on Alcohol consumption and dependency can be found at our entry here;
  • Full data on Smoking can be found at our entry here;
  • Substance Use disorders are often classified within the same category as Mental Health disorders — data on mental health and neurodevelopmental disorders can be found at our entry here.

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.

Substance use disorders

Definition of substance use disorders

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). 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 – health burden as a result of tobacco smoking is treated separately.

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.

Prevalence of substance use disorders

The series of charts present IHME data on the prevalence and number of people with any substance use disorder; this is the sum of alcohol and other drug use disorders. More detailed focus on alcohol use disorders can found at our entry on Alcohol Consumption; more detailed focus on other drug disorders are covered later in this entry.

The prevalence of substance use disorders is highest across Eastern Europe and the United States, occurring in 5-6 percent of the population. This means around 1-in-20 suffers from substance dependency. Across Western and Central Europe, the Americas and Oceania, this prevalence typically ranges from 2-5 percent. Across Africa, the Middle East and Asia this prevalence is typically lower at 1-2 percent. When we look at gender differences in substance use disorders we see that in every country the prevalence is greater in men than women.

It’s estimated that globally, around 164 million people had an alcohol or drug use disorder in 2016. The number with a substance use disorder differentiated by gender can be found here; globally around 68 percent (111 million) of those with a substance use disorder were male.

Deaths from substance use

The chart provides an overview of the direct death rates reported to occur from substance use disorders. It has been strongly argued that such metrics significantly underestimate the true mortality impact of such disorders.1

These mortality metrics only account for direct deaths from alcohol and drug use. However, suicide deaths are also strongly linked — although not always attributed to — mental health and substance use disorders. 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 alcohol, opioid, or psychostimulant dependence has an increased risk of suicide of 10, 7 and 8, respectively relative to an individual without. It is recognised that a given share of suicide deaths are attributed to this group of disorders; including this proportion of suicides would significantly increase the total attributed number of deaths.

Globally its estimated that around 318,000 deaths in 2016 were the direct result of a substance use disorder. The breakdown of these deaths by alcohol versus other drugs by country can be found here.

Disease burden from substance use disorders

The metric of mortality fails to capture the true health and wellbeing costs of mental health disorders. In the charts we present data on the attributed ‘disease burden‘ (measured in Disability-Adjusted Life Years; DALYs). This metric considers not only death rates, but also years lived with disability or health burden. As a share of total disease burden, substance use disorders typically account for 1-5 percent, but reaches over 5 percent in the United States.

DALY rates by country and over time from substance use disorders can be found here.

Alcohol use vs. drug use disorders

Do countries with high rates of alcoholism also have high rates of other drug use disorders? Or does a high prevalence in one mean a low prevalence in the other?

In the chart we see the share of the population with alcohol dependency versus the share with a drug use disorder (not including alcohol or tobacco). As we see, there is no clear relationship between the two; whilst most countries have a higher prevalence of alcohol dependence relative to other drugs, this is not true for all countries. It is also the case that a given country having a high rate of alcoholism does not imply it also has high rates of other drug use disorders (or vice versa).

Overall we see two clear outliers: Russia has notably high rates of alcoholism, and the United States high prevalence of other drug addiction.

Alcohol use disorders

The prevalence of alcohol use disorders across the world is shown in the chart. It’s estimated that globally around 1.4 percent of the population have an alcohol use disorder. At the country level, as shown in the chart, this ranges from around 0.5 to 5 percent of the population. In Russia, for example, the prevalence is 4.6 percent meaning that almost 1-in-20 have an alcohol dependence at any given time.

The remainder of this entry focuses on other drug use disorders (excluding alcohol). Full data on alcohol use disorders can be found at our entry on Alcohol Consumption.

Drug use disorders

Definition of drug use disorder

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.

Prevalence of drug use disorders

It’s estimated that globally around 0.9 percent 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.

The highest share experience opioid addiction, accounting for around 55 percent globally; cannabis addiction accounts for approximately one-quarter.

In the chart we see the difference in the share of males versus the share of females with a drug use disorder. In every country we see that men are more likely to have a drug addiction than women.

Deaths from drug use disorders

As was covered for total substance use deaths, the statistics here cover only direct death rates reported to occur from drug use disorders. This underestimates the total mortality impact of drug addiction because it does not account for indirect (but sometimes connected) deaths from suicide.2

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.

Recent overdose rates in the United States

In recent years there has been a significant increase in overdose rates in the United States — particularly from the category of 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, these are not age-standardized (so do not assume a constant age structure over time).

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, overdose rates have more than tripled.

Disease burden from drug use disorders

Using the measure of deaths fails to capture the true health consequences of drug use disorders. In the charts we present data on the attributed ‘disease burden‘ (measured in Disability-Adjusted Life Years; DALYs). This metric considers not only death rates, but also years lived with disability or health burden.

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.

Risk factors for substance use disorders

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.3

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.4

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.5,6,7

The impulsivity trait of ADHD in particular is identified as an important vulnerability for later onset of substance use disorders.8

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).

Mental health disorders as a risk factor for substance dependency

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).9

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.10

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.

Are drug use disorders more common in young people?

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 several multiples 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 recurring 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.11,12

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.13,14

Such attributes, combined with social pressures can in many cases lead to more frequent substance use (and the potential for development into 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.15

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.

Data Quality, Definitions & Measurement

Data availability on substance use disorders

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.16

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.

Data Sources

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: 1990 – 2016
  • 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.

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/

Further Guidance and Support

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: 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