Substance use disorder (SUD) is a complex condition involving the uncontrolled use of a substance, despite harmful consequences. Learn more about substance use disorders including the symptoms, and how they can be managed and treated.

What is substance use disorder?

A substance use disorder (SUD) occurs when someone loses the ability to control their use of a substance such as drugs, medication, alcohol or tobacco, causing harm to themselves or others. These substances activate the brain’s reward system, producing pleasurable feelings, which can lead to intense cravings. A substance use disorder can result in a person being unable to function normally day-to-day.

What are the main types of substance use disorder?

Substance use disorders are diagnosed based on the primary substance being misused. There are two main types of substance use disorder:

  • Alcohol use disorder: Alcohol is one of the most commonly used intoxicating substances. When someone misuses alcohol (often referred to as alcoholism) they lose control over how much alcohol they consume. They may also experience withdrawal symptoms when they are not drinking. Alcoholism can cause serious health conditions and may result in damage to organs in the body including the liver, heart, or the brain. Alcohol use disorder can also lead to destructive behaviour and unintended consequences, including family disputes, violence, accidents and injuries, unsafe sex, loss of personal possessions (e.g. wallet, handbag, mobile phone, and money), drunk driving, and absences from work or education.
  • Drug use disorder: Often referred to as drug addiction, this is a chronic condition that is difficult to control. When someone is addicted to drugs, they cannot resist the urge to use them, no matter how much damage they may cause. Drug addiction may include illegal drugs, but it can also involve prescription medications or a combination of both. Drugs such as cocaine, heroin, methamphetamines, benzodiazepines, steroids, and inhalants are highly addictive. They can lead to a substance use disorder very quickly. Drug addiction leads to changes to the brain over time which can make it very difficult to resist the intense urges to take drugs. That is why people who are addicted to drugs may relapse when they have tried to stop. Drug use disorder can have a devastating effect on people’s lives, leading to relationship problems, poor work or academic performance, issues with personal hygiene, increased impulsivity and risk-taking, and loss of interest in hobbies and activities.

How many people have substance use disorders?

Alcohol consumption is responsible for three million deaths each year globally, according to the World Health Organization. Overall, alcohol use disorders are responsible for 5.1% of the global burden of disease. Alcohol is the main risk factor for premature mortality and disability among people aged 15-49, accounting for 10% of all deaths in this age group.

The World Health Organization reports that about 270 million people (or about 5.5% of the global population aged 15-64) used psychoactive drugs in the previous year and about 35 million people are estimated to have drug use disorders. It is estimated that about half a million deaths every year are due to drug use, equating to 350,000 male deaths and 150,000 female deaths.


The symptoms of substance use disorders vary from person to person and can also depend on the type of addiction.

What are the symptoms of substance use disorder?

There are several signs and symptoms of substance use disorder that are common to most types of addiction. These include:

Behavioural and social changes:

  • Secretive or dishonest behaviour 
  • Lack of motivation to do anything, apathy
  • Changes in eating habits or sleeping patterns
  • Losing interest in hobbies and activities
  • Withdrawing from friends and family
  • Poor performance or attendance at work
  • Misusing substances in potentially dangerous situations (e.g. driving or operating machinery)
  • Making excuses for substance misuse (e.g. celebrating or stress relief)
  • Neglecting responsibilities at home or work
  • Borrowing or stealing money
  • Erratic behaviours

Psychological changes:

  • Sudden mood swings 
  • Personality changes such as irritability or angry outbursts
  • Feelings of hyperactivity or agitation 
  • Appearing anxious, afraid or paranoid for no specific reason 
  • Issues with concentration 
  • Defensiveness
  • Poor judgement 
  • Low self-esteem
  • Feelings of hopelessness 
  • Worsening of existing mental health conditions such as anxiety or depression

Physical changes:

  • Sudden weight loss or weight gain 
  • Bloodshot eyes 
  • Dilation of the pupils (mydriasis)
  • ‘Puffiness’ of the face 
  • Unusual skin colour 
  • Bad breath
  • Shakes or tremors 
  • General deterioration in physical appearance 
  • Injection marks (with drug misuse)

What are the stages of substance use disorder?

People who become addicted to substances such as alcohol or drugs typically go through four stages of abuse. An understanding of the stages of substance use disorder can help people recognise if they have a problem and need to get help before they become dependent on the substance. The four main stages are:
  1. Experimentation: Substance abuse starts with experimentation or voluntary use. In teenagers and younger adults, the substance is usually bought and tried with friends and is often in response to peer pressure. Older people may start to self-medicate in response to problems in their personal life, such as separation, divorce, bereavement or losing a job. At this stage, the use of drink or drugs is infrequent.
  2. Regular to risky use: This stage is characterised by use on a frequent basis. It may not necessarily occur every day, but the use of the substance may follow a predictable pattern (e.g. every weekend) or a predictable situation (e.g. when feeling bored, lonely, anxious or upset). The use starts to become risky when it leads to emotional, physical or social problems. It may result in problems at work, relationship issues, accidents and injuries, drink driving, and other serious unintended consequences.
  3. Dependence: At the dependence stage, the person will continue using the substance regularly despite the physical, social and emotional harm it is causing. Many people who are dependent on alcohol or drugs are still able to hold down jobs, maintain relationships with family and friends, and limit their consumption at certain times. However, they will find it difficult to recognise the effects of their substance use on everyone around them. Some of the main signs of dependence include:
    • Failing to fulfil responsibilities
    • Repeatedly drinking or using drugs in dangerous situations, such as driving or operating machinery
    • Developing a tolerance so that more alcohol or more drugs are required to have the same effect
    • Experiencing withdrawal symptoms
  4. Addiction: When someone is addicted, their use is out of control. The symptoms of addiction include uncontrollable cravings, constantly looking for ways to obtain alcohol or drugs, and use that persists even in the worst circumstances. Addiction is a progressive condition that worsens over time if it is left untreated.

What are the early signs of substance use disorders?

It is important to spot the early warning signs of a substance use disorder in order to get help as soon as possible.

Alcohol abuse early signs may include:

  • Blackouts during periods of drinking 
  • Repeated conflicts with family, friends and co-workers
  • Mood swings
  • Using alcohol to relax, deal with problems, get to sleep, or improve mood
  • Symptoms such as headaches, stomach problems, anxiety, and insomnia when not drinking
  • Trembling hands 
  • Reddened complexion or broken capillaries on the face 
  • Bloodshot eyes 
  • Sudden weight loss or weight gain 
  • Neglecting personal grooming habits
  • Slurred speech 

Drug abuse early signs may include:

  • Neglecting responsibilities in family life, work or education
  • Relationship issues 
  • Using drugs in potentially hazardous situations such as driving or operating machinery
  • Taking part in high-risk behaviours such as using dirty needles or having unprotected sex
  • Problems with the law (e.g. stealing to buy drugs or anti-social behaviour)
  • Dilated pupils 
  • Nosebleeds 
  • Sudden weight loss or weight gain 
  • Loss of personal hygiene 
  • Incoherent speech
  • Shaking or trembling

Causes, risk factors and life expectancy

Like many mental health conditions, there are several factors that may lead to substance use disorders. 

What causes substance use disorder?

The exact cause of substance use disorders is not known. Instead, there may be many factors involved, including:

  • Environment: A family situation, including their beliefs, values and attitudes, or socialising with a particular peer group can encourage substance use.
  • Mental health: Emotional distress, anxiety, depression, post-traumatic stress disorder, low self-esteem, or other psychological issues can all be a factor.
  • Genetics: Substance use disorders can sometimes run in families.

Is substance use disorder hereditary?

Substance use disorders are moderately to highly heritable. If someone has a blood relative, such as a parent or sibling, with an alcohol or drug addiction they have a greater risk of developing a substance use disorder. Genetic traits may speed up or delay the disorder’s progression.

Who gets substance use disorders?

People of any age, sex, background or economic status can become addicted to alcohol or drugs, although it is more common in people exposed to environmental, mental health or genetic risk factors.

How long can you live with a substance use disorder?

Although people can live with a substance use disorder, it is known to be a risk factor for premature death. These deaths can be caused by diseases and injury, including suicide, liver disease, hepatitis, cancer and HIV brought on as a result of excessive substance use. 

Globally, illicit drug use is responsible for over 585,000 premature indirect and direct deaths each year and 42% of all deaths are in people younger than 50 years. 

It is estimated that 2.84 million people die prematurely around the world every year as a result of alcohol consumption. Europe has the highest proportion in the world of total ill health and premature death due to alcohol and in Eastern Europe nearly one-third of deaths are attributed to alcohol consumption.4

Globally, almost three quarters of those dying from premature deaths due to alcohol are younger than 70 years and 28% are younger than 50 years.


Substance use disorders are usually diagnosed through a doctor’s evaluation, but some people will also self-report their problem if they are looking for help.

How is substance use disorder diagnosed?

Substance use disorder is diagnosed with a thorough evaluation, which usually includes an assessment by a mental health professional. Substance use can be checked using blood or urine testing, but the outcomes of these tests are not an indication of addiction.

Test to diagnose substance use disorder

There are a variety of questionnaires that mental health professionals can use to undertake their clinical evaluation to assess problematic alcohol and substance use.

These include the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) developed for the World Health Organization to assist with early identification of substance use disorders, the Alcohol Use Disorders Identification Test (AUDIT) to identify the early signs of harmful drinking and mild dependence, the Drug Use Disorders Identification Test for self-administered screening for drug-related problems, and the CRAFFT Screening Test designed to assess substance-related risks in adolescents.

Treatment and medication

Treatment and medication for substance use disorders can be used to help people withdraw from the substance they are addicted to and help to prevent relapse.

How is substance use disorder treated?

Treatment for substance use disorder depends on personal circumstances and what substances someone is addicted to. A treatment plan may include a number of different treatments and strategies.


The field of addiction medicine in Europe continues to progress, particularly in the development of new treatment interventions, which help to provide a wide range of options for people with substance use disorder.

Medication can be used to help re-establish normal brain function and decrease cravings. It is available for treating addiction to opioids (including heroin and prescription pain relievers), nicotine and alcohol.

There are no specific approved medications to treat stimulant addiction (cocaine, methamphetamine, and cannabis dependence), but advances are being made in the development of medication to treat these disorders.

If people use more than one drug, they will need treatment for each substance they use.

Medication used to treat substance use disorders includes:

  • Opioids:Some opioids are used to treat opioid addiction by acting on the same parts of the brain as heroin and morphine, helping to suppress withdrawal symptoms and reduce cravings. Others can be used to block the effects of opioids at their receptor sites in the brain involved with rewarding effects of drug use and cravings. These can be used for people with opioid or alcohol addiction.
  • Alcohol antagonists:Used to discourage drinking, alcohol antagonists cause unpleasant effects in a person who drinks even a small amount of alcohol, including headaches, vomiting, chest pain, blurred vision, breathing difficulties and anxiety.
  • Sulfonic acids:Certain sulfonic acid medicines are used to treat alcoholism in people who have stopped drinking by restoring the natural balance of chemicals in the brain. This helps to improve adherence to not drinking and overall abstinence from alcohol.
  • Smoking cessation aids:Medicine used for smoking cessation works by blocking the enjoyable effects of nicotine on the brain, preventing people feeling pleasure when smoking.


Many behavioural or talking therapies can be used to help patients with substance use disorder alongside other interventions. These help people to modify their attitudes and behaviours to drug use, increase healthy life skills and continue with other additional treatment. These therapies include:

  • Cognitive behavioural therapy (CBT):CBT is a talking therapy to help people manage their problems by changing the way they think and behave. It can help people to recognise, avoid or cope with situations where they might usually use drugs.
  • Motivational interviewing or incentives: This involves a therapist using positive reinforcement to support behaviour change by guiding people to become aware of their own aspirations for change and inspiring them to be self-motivated and make their own positive decisions.
  • Counselling: Counselling can be provided in a group or individual setting. It focuses on looking at new ways of coping with drug cravings and addressing any underlying causes for drug use.
  • Multi-dimensional family therapy: This type of therapy is designed for adolescents with drug problems and their families. It can look at the influences on a young person’s substance use patterns and help improve family life.
Residential treatment is also available for people with substance use disorders. This can include short-term stays focussing on detoxification in a community-based setting, longer-term therapeutic communities where people work with others to look at their understanding, attitudes and behaviour, or recovery housing to help people make the transition from residential treatment to independent life.

Substance users can also join support groups such as Alcoholics Anonymous or Narcotics Anonymous, where like-minded people support each other with recovery and continued abstinence from drugs or alcohol.


People with substance use disorder typically suffer from nutrient deficiencies because they tend to eat less nutrient-rich food and their body has a lower capacity to absorb nutrients because of the effects of drugs or alcohol.

Substance users in recovery should increase their intake of nutrients to help their body build and maintain healthy organs and fight off infection. They are advised to maintain regular mealtimes, eat foods low in fat, and eat more protein, complex carbohydrates and fibre, as well as reducing caffeine intake and stopping smoking if possible. In addition, dehydration is common during recovery from substance use so it is important to drink plenty of fluids during and in between meals.

Improving and maintaining good eating habits is also important because people in recovery may not recognise the difference between hunger and substance craving, which can lead to a high chance of relapse.


People with substance use disorders can find that exercise is helpful as a distraction from cravings. Taking part in physical exercise can also help people affected by substance use to develop a healthier lifestyle, which has been shown to improve their mental and physical health.

Moderate and high-intensity aerobic exercise such as brisk walking, playing tennis, running or skipping and mind-body exercise like yoga can be an effective part of a combined treatment plan for people with substance use disorders.

In addition, exercise regimes can add structure to a day and help people form positive social connections that can improve their recovery and overall wellbeing.


For substance use disorders, the main goal of prevention is to delay the first use of drugs or alcohol during adolescence.

It is important to address multiple risk factors which can be common in many areas of adolescent life, such as peer pressure, as well as focus on increasing protective factors, such as school support, to help young people resist the temptation to try drugs or alcohol.

Prevention interventions are also necessary to prevent people who already use some drugs from moving onto other drugs, and to prevent people who use drugs on an occasional basis from using them excessively.

The international classification of prevention interventions used in the United Nations Office on Drugs and Crime standards includes the following prevention strategies:

  • Universal: Universal prevention strategies are delivered to large groups or an entire population (e.g. by TV advertising or at school) to prevent or delay the start of substance use.
  • Selective: Selective prevention serves specific sub-populations whose risk of substance misuse is known to be higher than average, particularly among young people.
  • Indicated: Indicated prevention is aimed at people who are already using substances and may be showing signs of future problematic use.

Targeting each population group with relevant resources and messages can help prevent substance use and associated problems from starting or escalating.

Scientific studies

Research into substance use continues to progress in a number of key areas including evidence-based treatment practices, addiction treatment outcomes, addiction, psychiatry and the brain, addictive substances such as prescription opioids and heroin, and substance abuse in adolescents and other groups, as well as recovery management looking at how earlier detection and re-intervention can improve long-term outcomes.

Researchers are also looking at personalising treatment of substance use disorders, while noting that for meaningful recovery to occur, a substance user will need to integrate into a socially meaningful environment. With the understanding that addiction is influenced by genes, development, and social factors, treatment could in the future be personalised to accommodate each individual’s situation.

Referenced sources

  1.  World Health Organization. Alcohol fact sheet. Accessed March 2021.
  2.  Bevilacqua L, Goldman D. Genes and addictions. Clin Pharmacol Ther. 2009;85(4):359-361. doi:10.1038/clpt.2009.6
  3.  Ritchie H, Roser M. Opioids, cocaine, cannabis and illicit drugs. Our World in Data. Published April 2018. Accessed March 2021.
  4. Ritchie H, Roser M. Alcohol Consumption. Our World in Data. Published April 2018. Accessed March 2021.
  5.  Metz VE, Brandt L, Unger A, Fischer G. Substance abuse/dependence treatment: a European perspective. Subst Abus. 2014;35(3):309-320. doi:10.1080/08897077.2014.909377
  6.  Douaihy AB, Kelly TM, Sullivan C. Medications for substance use disorders. Soc Work Public Health. 2013;28(3-4):264-278. doi:10.1080/19371918.2013.759031
  7. Jeynes KD, Gibson EL. The importance of nutrition in aiding recovery from substance use disorders: A review. Drug Alcohol Depend. 2017;179:229-239. doi:10.1016/j.drugalcdep.2017.07.00
  8. Mahboub N, Rizk R, Karavetian M, de Vries N. Nutritional status and eating habits of people who use drugs and/or are undergoing treatment for recovery: a narrative review. Nutrition Reviews. 2020;nuaa095. doi:10.1093/nutrit/nuaa095
  9.  Cabrera I. Role of exercise in managing substance use disorders. Prescriber. 2020;31:15-19. doi:10.1002/psb.1841
  10. Wang D, Wang Y, Wang Y, Li R, Zhou C. Impact of physical exercise on substance use disorders: a meta-analysis. PLoS One. 2014;9(10):e110728. doi:10.1371/journal.pone.0110728
  11. Hazelden Betty Ford Foundation. Addiction Research. Accessed March 2021.
  12.  Dennis ML, Scott CK, Laudet A. Beyond bricks and mortar: recent research on substance use disorder recovery management. Curr Psychiatry Rep. 2014;16(4):442. doi:10.1007/s11920-014-0442-3
  13.  Nora D, Volkow MD. Personalizing the treatment of substance use disorders. American Journal of Psychiatry. 2020;177(2):113-116. doi:10.1176/appi.ajp.2019.19121284
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