Skip Navigation

Drugs, Risks and the Nervous System

Drugs, Risks and the Nervous System

Adolescents take more risks when consequences are unknown.
© Sergey Mironov.

  • Grades:
  • Length: 60 Minutes


Students estimate the risks associated with different events and compare their estimates to the real probabilities.

This activity is from the Brain Chemistry Teacher's Guide. Lessons in the guide are designed for use with students in grades 6–8, but they also may be used with other grade levels as appropriate.

Teacher Background

People perceive risks differently, depending on the nature of the risk and their individual experiences. Risk perceptions are strongly influenced by issues of choice and control; risks often seem “riskier” to people if they have not voluntarily chosen to bear them. Conversely, people are more willing to accept or ignore risks that they choose voluntarily, especially if the immediate benefit seems to outweigh the potential for negative outcomes much later in time. In the case of chemical substances that affect the brain, the risks can be very high indeed.

It is important to note that most people begin to use brain-altering chemicals voluntarily. Over time, however, the brain and body may adapt to the effects of a chemical. This can create a new “normal” state, adjusted to the presence of the introduced substance. This adaptation may lead to a physical dependence on the substance, such that the individual requires the chemical to function normally.

For example, more than 80 percent of the current US population chooses to consume the stimulant caffeine in coffee and/or cola drinks because of its taste and/or perceived enhancement of mental and physical performance. Eventually, most caffeine consumers develop a dependence on its stimulating effects and experience mild withdrawal symptoms, such as sleepiness and headaches, when they do not have caffeine. Other chemicals have more dramatic effects on the brain and body, affecting the brain’s natural reward centers, which are responsible for generating feelings of pleasure or well-being. However, feelings of euphoria, comfort or pleasure often decrease or disappear after the first few uses of the substance.

Drugs that act on areas of the brain related to sensations of pleasure are sometimes used inappropriately by people. Unfortunately, continued drug use actually changes the way the brain works. In some cases, it can cause permanent changes in the structure and function of the brain. This is the biological basis of addiction.

Many mind-altering chemicals abused by children and adults in the US lead to permanent changes in the brain that lead to addiction, and also may cause damage to other parts of the body. Marijuana use can alter memory regions of the brain and affect coordination and the senses in the short term. Heroin changes the way nerve cells in the brain receive and process messages. Inhalants, which are taken up by fatty tissue in the body, damage or destroy the fat-containing myelin sheath on nerve cell axons and disrupt nervous system communications, sometimes permanently. LSD can contribute to the development of chronic mental disorders. Alcohol, which depresses physical and mental abilities, damages many tissues throughout the body, including the liver and the brain. Alcohol also is a major contributing factor to automobile accidents because it affects coordination and judgment. Nicotine, a stimulant in tobacco, is a very addictive substance that can damage the circulatory system. However, the greatest health risk from smoking comes from other compounds in cigarette and cigar smoke that are linked to development of lung and other cancers.

Objectives and Standards


  • Perception of risk is affected by issues of personal choice and control.

  • Many chemicals influence the function of the nervous system.

  • Health risks associated with tobacco, alcohol and other drugs of abuse often are underestimated.

Science, Health and Math Skills

  • Predicting

  • Sorting and classifying

  • Comparing

  • Sequencing

  • Inferring

  • Understanding probability

Materials and Setup

Materials per Group of Students

  • Roll of clear tape, 0.5 in.

Materials per Student

  • Pair of scissors

  • Sheet of paper, 8.5 in. x 11 in.

  • Copy of “What Are the Odds?” and “The Risks Are Real” student pages


  1. Make photocopies of the student pages (one set for each per student).

  2. Begin with a class discussion, followed by students working in groups of four to complete the activity.

Procedure and Extensions

  1. Begin with a class discussion of the previous activity in which students simulated the effects of chemicals on neuron signaling. Ask, What are examples of substances that change the way the brain works or how a person feels? Give students time to think of some of the most common examples, such as alcohol, coffee and soft drinks with caffeine, cigarettes (nicotine), marijuana, inhalants (“sniffing” glue, paint or aerosols), etc.

  2. Follow by asking, Do you think people evaluate possible health risks when they take a substance that affects the brain? Why or why not? Do you think they should? 

  3. Tell students that one way to quantify risk is to state it as a probability that something will occur. For example, when students rolled a die in the activity, "Neurotransmitters Contain Chemicals," they had a one in six chance of rolling a “two” on any given toss because the die has six sides. Explain that by studying how frequently events have happened in the past, scientists and statisticians have been able to calculate the risk of many different types of occurrences.

  4. Give each group of students a copy of the “What Are the Odds?” page and have them read all of the statements. Have students cut the statements into strips (so that they can be rearranged easily). Next, have students discuss within their groups how likely it is that each event will occur.

  5. Students should rank the events numerically, from most likely to occur to least likely. The number “1” should be given to the most likely event. Have students place the strips in order of likelihood from most risk (top) to least risk (bottom). You may want to provide tape and a separate sheet on which students can arrange and secure their strips.

    Note. Tell students that some items have the same odds.

  6. Discuss students’ predictions briefly by asking which events they placed at the tops and bottoms of their lists. Let each group share some of its predictions and the reasoning behind the choices. Allow student groups to rethink or revise their predictions based on the discussion.

  7. Distribute a copy of “The Risks Are Real” page to each group and ask students to compare their predictions to the actual risk calculations.

  8. Conclude by discussing the actual risks as compared to students’ predictions. Ask guiding questions such as, Which ranking surprised you the most? Which were you able to predict most accurately? Do you think you or any of your friends might be ignoring long-term risks because you are making choices based on short-term benefits?

Related Content

  • Brain Chemistry

    Brain Chemistry Teacher Guide

    Students learn about the brain, neurons, chemical communication in the body, and how our choices can affect brain function and performance. (9 activities)

  • Brain Chemistry Explorations

    Brain Chemistry Explorations Reading

    Extension activities designed for use in class (see "Sample Sequence" in the teacher's guide) or the magazine may be taken home to share with family and friends.

  • Legacy of Lost Canyon

    Legacy of Lost Canyon Reading

    Adolescent friends investigate ancient cave ruins, and learn how and why drugs were used to create cave art.


NIH Blueprint for Neuroscience Research Science Education Award, National Institute on Drug Abuse, and NIH Office of the Director

The Learning Brain: Interactive Inquiry for Teachers and Students
Grant Number: 5R25DA033006

Science Education Partnership Award, NIH

Filling the Gaps: K-6 Science/Health Education
Grant Number: 5R25RR013454