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Symptoms and Signs of Drug Abuse

  1. Table of ContentsPrint
  2. Recognizing the Signs of Substance Abuse
  3. Illicit Drugs
  4. Prescription Drugs

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Recognizing the Signs of Substance Abuse

Drug abuse affects people from all walks of life and all socioeconomic statuses. Whatever the reason a person starts taking drugs, whether recreationally or as prescribed, tolerance and dependence may develop for some people—sometimes before the user even realizes it.1

When a full-blown substance-use disorder (SUD) develops, it can be extremely difficult to stop using drugs without effective professional treatment.2 Drug use can wreak havoc on the body and mind and may eventually become deadly. When you realize that you or someone you love has a problem, it's essential to get help right away. There is no shame in admitting that you need treatment for drug use; doing so can be life-saving.

Use of most substances will produce noticeable signs and symptoms. These may include physical or behavioral symptoms—most likely both.

Physical and behavioral symptoms of drug abuse.

Physical Symptoms

Some of the most noticeable symptoms of drug use are those that affect the body’s inner workings. For example, your body’s tolerance to a drug occurs when a drug is used long or often enough that increased quantities or strengths are required to achieve the previous effects.1

Individuals using a drug for a high may come to take such high doses to overcome a tolerance that they subject themselves to potentially fatal overdose.3“checking
Changes in appearance can be additional clues to possible drug use and may include:4

  • Bloodshot or glazed eyes.
  • Dilated or constricted pupils.
  • Abrupt weight changes.
  • Problems sleeping or sleeping too much.

Signs will vary based on the substance.

Behavioral Symptoms

Drug use tends to significantly alter a person's behavior and habits. Some drugs can impair the brain's ability to focus and think clearly.5

Changes in behavior, such as the following, can indicate a problem with drug abuse:4,6“depressed

  • Increased aggression or irritability.
  • Changes in attitude/personality.
  • Lethargy.
  • Depression.
  • Sudden changes in a social network.
  • Dramatic changes in habits and/or priorities.
  • Involvement in criminal activity.

Learning to recognize the physical or behavioral signs of drug use can help prevent the problem from progressing further.

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Illicit Drugs

Click on any substance below to find out the typical signs and symptoms of abuse and addiction for that substance and how to find help.

How much do you know about some of the most commonly abused drugs? Learn the signs and symptoms now.

Prescription Drugs


    1. National Institute on Drug Abuse. (2018). Is there a difference between physical dependence and addiction? 
    2. National Institute on Drug Abuse. (2018). Principles of Effective Treatment. 
    3. Pennsylvania Department of Drug and Alcohol Programs. (n.d.). Overdose Overview.
    4. New York State Department of Health and the Office of Alcoholism and Substance Abuse Service. (n.d.). How do I Know? I think My Child is Using Alcohol and/or Drugs. 
    5. National Institute on Drug Abuse. (2018). Drugs and the brain
    6. National Institute on Drug Abuse. (2007, January). Bringing the Power of Science to Bear on Drug Abuse and Addiction: Drugs Have Long-term Consequences. 
    Last updated on April 26, 2019
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