Drug Use and Addiction

Source: MedlinePlus Health Topics, U.S. National Library of Medicine

Last synced 8/12/2026Status: primary verified

What are drugs? 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. What is drug use? Drug use, or misuse, includes: Using illegal substances, such as: Anabolic steroids Club drugs Cocaine Heroin Inhalants Marijuana Methamphetamines Misusing prescription medicines , including opioids . This means taking the medicines in a different way than your health care provider prescribed. This includes 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. Misusing over-the-counter medicines, including using them for another purpose or in a different way than you are supposed to. 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. What is drug 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. Does everyone who takes drugs become addicted? 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 beco

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This information is for general education and is not medical advice. Always talk to a licensed U.S. clinician about your situation, medications, or treatment decisions.