NIDA for Teens: The Science Behind Drug Abuse
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  • The NIDA Blog Team

    Q: What do cocaine and bacteria have in common?

    A: They both contaminate our cash.

    While most of the dollar bills you come into contact with would test positive for cocaine, that doesn’t mean that they were used to snort cocaine. In fact, less than 1 percent of people age 12 or older even use the drug.  

    It happens because cocaine is a very fine powder that easily transfers from bill to bill. One bill with cocaine on it can contaminate an entire cash drawer or ATM. It’s a little like someone with a cold—if he or she sneezes on you, the chances are good that you’ll catch what the individual has.

    Graphic of text saying, "Q: What do cocaine and bacteria have in common? A: They both contaminate our cash.”  Below that, text says, “Nearly 9 out of 10 dollar bills in the United States test positive for cocaine residue. The amount of cocaine found on money is usually minuscule—a nanogram to a milligram.” Beside the text is a graphic of 10, one-dollar bills with 9 of them containing red marks. Below that, text says, “Yet, less than 1% of people age 12 and older are using cocaine.” Beside the text is a graphic of 100 people and only 1 is colored red. Below that is a graphic of a person at an ATM with text beside it that says, “Cocaine is a very fine powder that easily transfers from one bill to another. It only takes one dollar that has any trace of cocaine to contaminate an entire ATM.” Below that, text says, “Researchers have identified more than 3,000 different types of bacteria on dollar bills.” Beside the text is a graphic of a one-dollar bill with a close-up of bacteria. Below that, text says, “Just another good reason to wash your hands!” Beside the text is a graphic of hands washing and a red check-mark.

    But don’t worry. Your stash of cash has only a tiny amount of cocaine on it—not enough to get you high or cause you to fail a drug test.

    And What About Bacteria?

    Well, germaphobes beware—researchers from New York University found hundreds of different bacteria on dollar bills. In all, they identified over 3,000 different types of bacteria that caused pneumonia, food poisoning, and staph infections. 

    Want To Know What’s in Your Pocket?

    Where’s George? allows users to enter and track dollar bills. It shows how far money can travel while it is in circulation. 

    So, the bottom line here is that money is dirty. And while cocaine is not likely to get on your skin from handling money, germs will. So, we suggest washing your hands frequently.







    Sources for Infographic:

    Biello, D. (2009 Aug 16). Cocaine contaminates majority of U.S. currency. Scientific American. Retrieved November 3, 2014, from

    Carlton, J. (2014).  The Dirty Money Project.  Mapping NYC’s MetaGenome: A Research Project at New York University.

    Oyler, J., Darwin, W.D., & Cone, E.J. (1996 Jul/Aug). Cocaine contamination of United States paper currency. Journal of Analytical Toxicology, 20(4):213–216. Retrieved November 3, 2014, from

    Substance Abuse and Mental Health Services Administration. (2014 Sept). Results From the 2013 National Survey on Drug Use and Health: Summary of National Findings, NSDUH Series H-48, HHS Publication No. (SMA) 14-4863: Rockville, MD: SAMHSA. Retrieved November 3, 2014, from

  • What Is Cocaine?

    lines of cocaine

    Also known as: “coke,” “Coca,” “C,” “snow,” “flake,” “blow,” “bump,” “candy,” “Charlie,” “rock,” and “toot”

    Cocaine is a powerfully addictive stimulant drug made from the leaves of the coca plant native to South America. Cocaine comes in two forms:

    • Powder cocaine is a white powder (which scientists call a hydrochloride salt). Street dealers often mix cocaine with other substances like cornstarch, talcum powder, or sugar. They also mix cocaine with active drugs like procaine, a chemical that produces local anesthesia (a local anesthetic that causes you not to feel pain in a specific area of the body) and with other stimulants like amphetamines.
    • Crack is a form of cocaine that has been processed to make a rock crystal that people smoke. The term “crack” refers to the cracking sound the rocks make when they are heated. To make crack, the powder cocaine is mixed with ammonia or baking soda and water and then heated to produce the crystal.
  • How Is Cocaine Used?

    Powder cocaine can be snorted up the nose or mixed with water and injected with a needle. Sometimes, powder cocaine is rubbed onto gums or other tissues in the body. Crack is smoked in a small glass pipe. The crystal is heated to produce vapors that are absorbed into the blood through the lungs.

    In order to keep the “high” going, people may take the drug repeatedly within a short period of time, at increasingly higher doses.

  • How Does Cocaine Affect the Brain?

    Stimulants like cocaine change the way the brain works by changing the way nerve cells communicate. Nerve cells, called neurons, send messages to each other by releasing chemicals called neurotransmitters. These neurotransmitters attach to molecules on neurons called receptors. (Learn more about how neurotransmitters work.)

    There are many neurotransmitters, but dopamine is the main one that makes people feel good when they do something they enjoy, like eating a piece of chocolate cake or playing a video game. It is then recycled back into the cell that released it, thus shutting off the signal. Cocaine prevents the dopamine from being recycled, causing a buildup of the neurotransmitter in the brain. It is this flood of dopamine that causes cocaine’s high. The drug can cause a feeling of intense pleasure and increased energy.

    With repeated use, stimulants can disrupt how the brain’s dopamine system works, reducing a person’s ability to feel any pleasure at all. People may try to make up for it by taking more and more of the drug to feel the same pleasure.

    After the "high" of the cocaine wears off, many people experience a "crash" and feel tired or sad for days. They also experience a strong craving to take cocaine again to try to feel better.

    Learn more about  how the brain works and what happens when a person uses drugs.

  • What Are the Other Effects of Cocaine?

    The surge of dopamine in the brain affects the body in a variety of ways:

    • Constricted blood vessels and dilated pupils
    • Higher body temperature
    • Higher blood pressure and faster heartbeat
    • Feeling sick to the stomach
    • Restlessness
    • Decreased appetite and, over time, a loss of weight
    • Inability to sleep
    • Increased risk of heart attack or stroke due to high blood pressure
    • Increased risk of HIV because of impaired judgment leading to risky sexual behavior
    • Strange, unpredictable behavior, panic attacks, or paranoid psychosis (losing touch with reality)

    How cocaine is used leads to different physical problems. For example, regularly snorting cocaine can lead to a hoarse voice, loss of the sense of smell, nosebleeds, and a constant runny nose. Cocaine taken by mouth can reduce blood flow in your intestines, leading to bowel problems. Injecting cocaine can increase a person’s risk of getting HIV, hepatitis C (a liver disease), and other diseases transmitted by blood contact.

  • Can You Get Addicted to Cocaine?

    Yes, repeated use can lead to addiction, a devastating brain disease where people can’t stop using drugs even when they really want to and even after it causes terrible consequences to their health and other parts of their lives. Using cocaine over and over can cause tolerance to the drug. This means that it takes more of the drug for the user to get the same high felt when first using it.

    Because a cocaine high usually doesn't last very long, people take it again and again to try to keep feeling good. Once addicted, people who are trying to quit taking cocaine might:

    • Act nervous and restless
    • Feel very sad and tired
    • Have bad dreams
    • Not trust people and things around them
    • Feel a strong need to take cocaine

    The right treatment, however, can help an addicted person control their cravings and stop using cocaine.

  • Can You Die If You Use Cocaine?

    Yes. In 2011, more than 4,600 people died from a cocaine overdose. Males are nearly three times more likely to die from a cocaine overdose than females.1

    Cocaine can be deadly when taken in large doses or when mixed with other drugs or alcohol. Cocaine-related deaths are often a result of the heart stopping (cardiac arrest) followed by stopped breathing. Abusing cocaine with alcohol or other drugs increases these dangers, including the risk of overdose. For example, combining cocaine and heroin (known as a “speedball”) puts a person at higher risk of death from an overdose.

    In rare instances, sudden death can occur on the first use of cocaine or soon after.

    1Centers for Disease Control and Prevention, National Center for Health Statistics. Underlying Cause of Death 1999-2011 on CDC WONDER Online Database, released 2014. Available at

  • How Many Teens Use Cocaine?

    For the most recent statistics on cocaine use among teens, see the results below from NIDA’s Monitoring the Future study.

    Swipe left or right to scroll.

    Monitoring the Future Study: Trends in Prevalence of Various Drugs for 8th Graders, 10th Graders, and 12th Graders; 2014 (in percent)*
    Drug Time Period 8th Graders 10th Graders 12th Graders
    Cocaine Lifetime 1.80 2.60 4.60
    Past Year 1.00 1.50 2.60
    Past Month 0.50 0.60 1.00
    Crack Cocaine Lifetime 1.20 [1.00] 1.80
    Past Year 0.70 [0.50] 1.10
    Past Month 0.30 0.30 0.70

    * Data in brackets indicate statistically significant change from the previous year.

    Source: University of Michigan, Monitoring the Future Study

    For more statistics on teen drug use, see NIDA’s Monitoring the Future study.

  • What Should I Do If Someone I Know Needs Help?

    If you or a friend are in crisis and need to speak with someone now, please call:

    • National Suicide Prevention Lifeline at 1-800-273-TALK (they don't just talk about suicide—they cover a lot of issues and will help put you in touch with someone close by).

    If you need information on treatment and where you can find it, you can call:

    For more information on how to help a friend or loved one, visit our Have a Drug Problem, Need Help? page.