Health Topic

Drug Use and Addiction

Drugs include prescription and over-the-counter medicines, alcohol, tobacco, and illegal substances. Repeated drug use can change the brain and lead to addiction.

Reviewed Reviewed by a registered pharmacistGeneral information

Also called: Drug abuse · Substance Use

Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.

About Drug Use and Addiction

Drugs are chemical substances that can change how your body and mind work. They include prescription medicines, over-the-counter medicines, alcohol, tobacco, and illegal drugs.

Drug use, or misuse, includes:

  • Using illegal substances, such as: Anabolic steroids
  • Club drugs
  • Cocaine
  • Heroin
  • Inhalants
  • Marijuana
  • Methamphetamines
  • Taking a medicine that was prescribed for someone else.
  • Taking a larger dose than you are supposed to.
  • Using the medicine in a different way than you are supposed to. For example, instead of swallowing your tablets, you might crush and then snort or inject them.
  • Using the medicine for another purpose, such as getting high.

Drug use is dangerous. It can harm your brain and body, sometimes permanently. It can hurt the people around you, including friends, families, and kids. If you are pregnant, it can harm your fetus. Drug use can also lead to mild, moderate, or severe substance use disorders. Substance use disorders are sometimes called addiction.

Drug addiction is a chronic brain disease. It causes a person to take drugs repeatedly, despite the harm they cause. Repeated drug use can change the brain and lead to addiction.

The brain changes from addiction can be lasting, so drug addiction is considered a "relapsing" disease. This means that people in recovery are at risk for taking drugs again, even after years of not taking them.

Not everyone who uses drugs becomes addicted. Everyone's bodies and brains are different, so their reactions to drugs can also be different. Some people may become addicted quickly, or it may happen over time. Other people never become addicted. Whether or not someone becomes addicted depends on many factors. They include genetic, environmental, and developmental factors.

Various risk factors can make you more likely to become addicted to drugs, including:

  • Your biology. People can react to drugs differently. Some people like the feeling the first time they try a drug and want more. Others hate how it feels and never try it again.
  • Mental health problems. People who have untreated mental health problems, such as depression, anxiety, or attention deficit/hyperactivity disorder (ADHD) are more likely to become addicted. This can happen because drug use and mental health problems affect the same parts of the brain. Also, people with these problems may use drugs to try to feel better.
  • Trouble at home. If your home is an unhappy place or was when you were growing up, you might be more likely to have a drug problem.
  • Trouble in school, at work, or with making friends. You might use drugs to get your mind off these problems.
  • Hanging around other people who use drugs. They might encourage you to try drugs.
  • Starting drug use when you're young. When kids use drugs, it affects how their bodies and brains finish growing. This increases your chances of becoming addicted when you're an adult.

Signs that someone has a drug problem include:

  • Changing friends a lot
  • Spending a lot of time alone
  • Losing interest in favorite things
  • Not taking care of themselves - for example, not taking showers, changing clothes, or brushing their teeth
  • Being very energetic, talking fast, or saying things that don't make sense
  • Quickly changing between feeling bad and feeling good
  • Having different eating or sleeping habits
  • Missing important appointments
  • Having problems at work or at school
  • Having problems in personal or family relationships

Treatments for drug addiction include counseling, medicines, or both. Research shows that combining medicines with counseling gives most people the best chance of success.

The counseling may be individual, family, and/or group therapy. It can help you:

  • Understand why the drug addiction began
  • See how drugs changed your behavior
  • Learn how to manage personal problems
  • Learn to avoid places, people, and situations where drugs are accessible

If you stop or cut back on drugs you've used for a while, you may display different symptoms for different drugs. This is called withdrawal. Medicines can help with the symptoms of withdrawal. For addiction to certain drugs, there are also medicines that can help you re-establish normal brain function and decrease your cravings.

If you have a mental disorder along with an addiction, it is known as a dual diagnosis. It is important to treat both problems. This will increase your chance of success.

If you have a severe addiction, you may need hospital-based or residential treatment. Residential treatment programs combine housing and treatment services.

Drug use and addiction are preventable. Prevention programs involving families, schools, communities, and the media may prevent or reduce drug use and addiction. These programs include education and outreach to help people understand the risks of drug use.

It sits within Substance Use and Disorders.

The lead U.S. institute for this subject is the National Institute on Drug Abuse.

When to speak to someone. Reading about a topic cannot tell you whether it applies to you. Speak to a doctor or pharmacist if symptoms are severe, sudden, getting worse, or simply not going away — and seek emergency care immediately for chest pain, breathing difficulty, sudden weakness or confusion, or a serious allergic reaction.

Research on Drug Use and Addiction

107 studies areregistered for this condition on ClinicalTrials.gov, the U.S. National Library of Medicine's public registry. A selection is below — the links go straight to the registry entry, not to a summary of ours.

What a registered study does and does not mean. Registration means a study exists and has been declared publicly. It says nothing about whether the treatment being tested works, is safe, or is available to you. Many studies find no benefit — that is what research is for. Never seek out an experimental treatment on the strength of a registry entry alone.

Research currently under way

Research already completed

Study data from ClinicalTrials.gov, a service of the U.S. National Library of Medicine. Retrieved 2026-07-30. Registry entries are supplied by study sponsors and investigators; ClinicalTrials.gov does not verify their scientific validity. PocketsInfo is not affiliated with, and not endorsed by, the NLM or the NIH.

Where to read more

Rather than paraphrase, we point you to the primary sources. Every link below is to a government health agency, a national institute or a recognised medical body — grouped by what you are trying to find out.

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Diagnosis and Tests

Treatments and Therapies

Prevention and Risk Factors

Living With

Related Issues

Statistics and Research

Clinical Trials

Medical subject headings

Clinicians and researchers index this subject under Drug Misuse, Substance-Related Disorders. These are the terms to use when searching medical literature.

This page is built from the MedlinePlus health topic record for Drug Use and Addiction, a service of the U.S. National Library of Medicine (NLM), National Institutes of Health. Information is from MedlinePlus.gov. PocketsInfo is not affiliated with, and is not endorsed by, the NLM or the NIH. Retrieved 30 July 2026.