Chapter 8: Drugs & Addiction

Why is it important to understand how different drugs impact the body and mind?

What are the risks associated with using drugs?

What causes addiction?

Chapter 8 Learning Outcomes

By the end of this chapter you will be able to:

  • Explain what occurs in the body when someone has an addiction.
  • Recognize risk factors for addiction
  • Compare and contrast health effects of common illicit drugs
  • Describe impacts of drug use on the individual, family, and community.
  • Identify treatments for drug abuse.

This chapter focuses on drug use and addiction.  Often addiction is associated with the consumption of addictive drugs, however addiction is broader than just the consumption of addictive substances and also includes behavioral addictions, such as the addiction to gambling, pornography, internet use, and exercise.  There is debate whether behavioral addictions and substance addictions should be grouped together. This chapter will begin with a focus on substance addiction and will end with a focus on behavioral addictions.

Drug Use and Drug Addiction

Drug addiction is a complex illness, many people don’t understand why or how other people become addicted to drugs. They may mistakenly think that those who use drugs lack moral principles or the willpower to quit without recognizing that drugs change the brain in ways that make quitting hard, even for those who want to.  In reality, drug addiction is a complex disease, and quitting usually takes more than good intentions or a strong will.  A person may initially choose to take the drug, however over time they are incapable of choosing not to take the drug.

Fortunately, researchers know more than ever about how drugs affect the brain and have found treatments that can help people recover from drug addiction and lead productive lives.

Drug Use and Overdose

The National Survey on Drug Use and Health (NSDUH)[1] is published each year to share statistics on drug use in the U.S.  Key findings from the 2020 annual report show that drug use is fairly common.

Among people aged 12 or older in year 2020:

  • 58.7 percent (or 162.5 million people) used tobacco, alcohol, or an illicit drug in the past month (current user).
  • 21.4 percent (or 59.3 million people) used illicit drugs in the past year.
  • Marijuana was the most commonly used illicit drug, with 17.9 percent (or 49.6 million people) using it in the past year.
  • 3.7 percent (or 10.3 million people) misused central nervous system (CNS) stimulants in the past year.
  • 3.4 percent (or 9.5 million people) misused opioids (heroin or prescription pain relievers) in the past year.
  • 3.3 percent (or 9.3 million people) misused prescription pain relievers in the past year.
  • 2.6 percent  (or 7.1 million people) used hallucinogens in the past year.
  • 14.5 percent (or 40.3 million people) had a Substance Use Disorder in the past year

Unfortunately both first time users and those who have an addiction are both at risk of possible drug overdose. Between 1999-2000 more than 932,000 people have died from a drug overdose.  Most recently, the majority of overdoses are caused by synthetic opioids. For example in 2020, about 92,000 drug overdose deaths occurred in the United States and 75% of the overdoses involved opioid use.  Data from just 24 states from January–June 2019 showed that Illicitly manufactured fentanyl, heroin, cocaine, or methamphetamine (alone or in combination) were involved in nearly 85% of drug overdose deaths.

Drug Addiction

Addiction is a chronic disease characterized by drug seeking and use that is compulsive, or difficult to control, despite harmful consequences. The initial decision to take drugs is voluntary for most people, but repeated drug use can lead to brain changes that challenge an addicted person’s self-control and interfere with their ability to resist intense urges to take drugs. These brain changes can be persistent, which is why drug addiction is considered a “relapsing” disease—people in recovery from drug use disorders are at increased risk for returning to drug use even after years of not taking the drug.

It’s common for a person to relapse, but relapse doesn’t mean that treatment doesn’t work. As with other chronic health conditions, treatment should be ongoing and should be adjusted based on how the patient responds. Treatment plans need to be reviewed often and modified to fit the patient’s changing needs.

What happens to the brain when a person takes drugs?

Most drugs affect the brain’s “reward circuit” by flooding it with the chemical messenger dopamine. This reward system controls the body’s ability to feel pleasure and motivates a person to repeat behaviors needed to thrive, such as eating and spending time with loved ones. This overstimulation of the reward circuit causes the intensely pleasurable “high” that can lead people to take a drug again and again.

As a person continues to use drugs, the brain adjusts to the excess dopamine by making less of it and/or reducing the ability of cells in the reward circuit to respond to it. This reduces the high that the person feels compared to the high they felt when first taking the drug, an effect known as tolerance, which involves taking more of the drug to try to achieve the same dopamine high. It can also cause them to get less pleasure from other things they once enjoyed, like food or social activities.

Long-term use can cause changes in other brain chemical systems and circuits that can negatively impact a persons learning, judgment, decision-making, stress, memory, and behavior.  Long-term use can also lead to drug dependence, where your body is used to functioning with the drug in your system.  If you are dependent on a drug and the drug is removed, it can cause withdrawals symptoms.   Withdrawal symptoms vary depending on the type of drug dependence and may include tremors (shaking), cravings, agitation, nausea, sweating, or changes in mood.

Despite being aware of these harmful outcomes, many people who use drugs continue to take them, which is the nature of addiction.

Why do some people become addicted to drugs while others don’t?

No one factor can predict if a person will become addicted to drugs. A combination of factors influences risk for addiction. The more risk factors a person has, the greater the chance that taking drugs can lead to addiction. For example:

  • Biology
    • The genes that people are born with account for about half of a person’s risk for addiction. Gender, ethnicity, and the presence of other mental disorders may also influence risk for drug use and addiction.
  • Environment
    • A person’s environment includes many different influences, from family and friends to economic status and general quality of life. Factors such as peer pressure, physical and sexual abuse, early exposure to drugs, stress, and parental guidance can greatly affect a person’s likelihood of drug use and addiction.
  • Developmental stages
    • Genetic and environmental factors interact with critical developmental stages in a person’s life to affect addiction risk. Although taking drugs at any age can lead to addiction, the earlier that drug use begins, the more likely it will progress to addiction. This is particularly problematic for teens. Because areas in their brains that control decision-making, judgment, and self-control are still developing, teens may be especially prone to risky behaviors, including trying drugs.

What are some consequences of Drug Abuse?

Drug abuse is a serious public health problem that affects many communities and families in some way. Each year drug abuse causes millions of serious illnesses or injuries among Americans.  Drug abuse also plays a role in many major social problems, such as drugged driving, violence, stress, and child abuse.  Drug abuse can lead to homelessness, crime, and missed work or problems with keeping a job. It harms unborn babies and destroys families.

Some people who are addicted don’t believe that they are sick and out of control, so they don’t look for treatment. They don’t see the problems they are causing themselves and those around them. Other people who are addicted are aware of the problem, but may be so upset and confused that they do not know how to ask for or get help.

Drugs don’t just hurt the person taking them. Everyone connected to the person can get hurt.  When you or a loved one abuse drugs, everyday life can feel out of control.

Drug abuse affects the family in many ways, including:

  • When a person has a drug problem, they have a disease that can hurt the family.
  • Drug abuse puts a lot of stress on parents, brothers and sisters, children, grandparents—anyone who is part of the home.
  • Family members might fight a lot because of the problems the drug abuse is causing.
  • The drug user might do and say things that upset neighbors and friends, and make the family ashamed.

When family members take drugs, you may experience situations such as:

  • You generally can’t count on them to do what they say they will do.
  • They may forget or get distracted because their focus is on getting and taking drugs.
  • They might lie or steal money to buy drugs.
  • They might get fired from their jobs.
  • They might not come home at night.
  • They may do bad things they would never do if they weren’t abusing drugs.

Drug abuse can cause many problems including: Fighting and violence in and outside the home; money problems; trouble at school; trouble at work, losing a job; trouble in relationships; child abuse, neglect; driving accidents; and arrests and jail.

Drug Facts

The following information provides short-term and long-term effects of various drugs along with the health-related issues.  Additional drug facts can be reviewed at The National Institute of Drug Abuse- Drug Facts website.


Marijuana is made from the hemp plant, Cannabis sativa. The main psychoactive (mind-altering) chemical in marijuana is delta-9-tetrahydrocannabinol, or THC.

Table 8.1 : Possible Health Effects of Marijuana
Time Effects
Short-term Enhanced sensory perception and euphoria followed by drowsiness/relaxation; slowed reaction time; problems with balance and coordination; increased heart rate and appetite; problems with learning and memory; hallucinations; anxiety; panic attacks; psychosis.
Long-term Mental health problems, chronic cough, frequent respiratory infections.
Other Health-related Issues Youth: possible loss of IQ points when repeated use begins in adolescence. Pregnancy: babies born with problems involving attention, memory, and problem solving.

Synthetic cannabinoids

Synthetic cannabinoids are human-made mind-altering chemicals that are either sprayed on dried, shredded plant material so they can be smoked or sold as liquids to be vaporized and inhaled in e-cigarettes and other devices. These products are also known as herbal or liquid incense, or synthetic marijuana (or fake weed).

Table 8.2: Possible Health Effects of Synthetic cannabinoids
Time Effects
Short-term Rapid heart rate, vomiting, violent behavior, suicidal thoughts, altered perception, symptoms of psychosis
Long-term Withdrawal symptoms: headaches, anxiety, depression, irritability
Other Health-related Issues Overdose may cause: toxic reactions, elevated blood pressure, reduced blood supply to the heart, kidney damage, and seizures Death may occur if mixed with synthetic opioids such as Fentanyl.


Cocaine is a powerfully addictive stimulant drug made from the leaves of the coca plant native to South America.

Table 8.3: Possible Health Effects of Cocaine
Time Effects
Short-term Narrowed blood vessels; enlarged pupils; increased body temperature, heart rate, and blood pressure; headache; abdominal pain and nausea; euphoria; increased energy, alertness; insomnia, restlessness; anxiety; erratic and violent behavior, panic attacks, paranoia, psychosis; heart rhythm problems, heart attack; stroke, seizure, coma.
Long-term Loss of sense of smell, nosebleeds, nasal damage and trouble swallowing from snorting; infection and death of bowel tissue from decreased blood flow; poor nutrition and weight loss from decreased appetite.
Other Health-related Issues Pregnancy: premature delivery, low birth weight, smaller head circumference. Risk of HIV, hepatitis, and other infectious diseases from shared needles.


Methamphetamine is an extremely addictive stimulant amphetamine drug.

Table 8.4: Possible Health Effects of Methamphetamine
Time Effects
Short-term Increased wakefulness and physical activity; decreased appetite; increased breathing, heart rate, blood pressure, temperature; irregular heartbeat.
Long-term Anxiety, confusion, insomnia, mood problems, violent behavior, paranoia, hallucinations, delusions, weight loss, severe dental problems (“meth mouth”), intense itching leading to skin sores from scratching.
Other Health-related Issues Pregnancy: premature delivery; separation of the placenta from the uterus; low birth weight; lethargy; heart and brain problems. Risk of HIV, hepatitis, and other infectious diseases from shared needles.

Prescription CNS Depressants

Prescription CNS depressants are medicines that include sedatives, tranquilizers, and hypnotics that slow down brain activity and can cause sleepiness and loss of coordination. Continued use can lead to physical dependence and withdrawal symptoms if use is stopped.  These includes drugs classified as Benzodiazepines, Non-Benzodiazepine Sedative Hypnotics, and Barbiturates.

Table 8.5: Possible Health Effects of CNS Depressants
Time Effects
Short-term Drowsiness, slurred speech, poor concentration, confusion, dizziness, problems with movement and memory, lowered blood pressure, slowed breathing.
Long-term Physical dependence, withdrawal, possibility of seizures from rebound effect.
Other Health-related Issues Sleep medications are sometimes used as date rape drugs (e.g. Rohypnol). Risk of HIV, hepatitis, and other infectious diseases from shared needles.
In Combination with Alcohol Further slows heart rate and breathing, which can lead to death.

Prescription CNS Stimulants

Prescription stimulants are medicines generally used to treat attention-deficit hyperactivity disorder (ADHD) and narcolepsy—uncontrollable episodes of deep sleep. They increase alertness, attention, and energy.

Table 8.6: Possible Health Effects of CNS Stimulants
Time Effects
Short-term Increased blood pressure and heart rate, increased breathing, decreased blood flow, increased blood sugar, and opened-up breathing passages.
Long-term Repeated misuse of prescription stimulants, even within a short period, can cause psychosis, anger, or paranoia.
Other Health-related Issues At high doses, prescription stimulants can lead to a dangerously high body temperature, an irregular heartbeat, heart failure, and seizures.

Prescription Opioids

Opioids are a class of drugs naturally found in the opium poppy plant.  Opioids are often used as medicines because they contain chemicals that relax the body and can relieve pain.  Opioids can cause euphoria and are often used non-medically, leading to overdose deaths.  Heroin is one of the world’s most dangerous opioids, and is never used as a medicine in the United States.

Table 8.7: Possible Health Effects of Opioids
Time Effects
Short-term Pain relief, drowsiness, nausea, constipation, euphoria, confusion, slowed breathing, death.
Long-term Physical dependence, possible brain damage.
Other Health-related Issues Pregnancy: Miscarriage, low birth weight, neonatal abstinence syndrome. Older adults: higher risk of accidental misuse or abuse because many older adults have multiple prescriptions, increasing the risk of drug-drug interactions, and breakdown of drugs slows with age; also, many older adults are treated with prescription medications for pain. Risk of HIV, hepatitis, and other infectious diseases from shared needles.
In Combination with Alcohol Dangerous slowing of heart rate and breathing leading to coma or death.


Heroin is an opioid drug made from morphine.  Prescription opioid pain medicines such as OxyContin® and Vicodin® have effects similar to heroin. Research suggests that misuse of these drugs may open the door to heroin use.

Table 8.8: Possible Health Effects of Heroin
Time Effects
Short-term Euphoria; warm flushing of skin; dry mouth; heavy feeling in the hands and feet; clouded thinking; alternate wakeful and drowsy states; itching; nausea; vomiting; slowed breathing and heart rate.
Long-term Collapsed veins; abscesses (swollen tissue with pus); infection of the lining and valves in the heart; constipation and stomach cramps; liver or kidney disease; pneumonia.
Other Health-related Issues Pregnancy: miscarriage, low birth weight, neonatal abstinence syndrome. Risk of HIV, hepatitis, and other infectious diseases from shared needles.
In Combination with Alcohol Dangerous slowdown of heart rate and breathing, coma, death.


Fentanyl is a powerful synthetic opioid that is similar to morphine but is 50 to 100 times more potent.  Like morphine, it is a medicine that is typically used to treat patients with severe pain, especially after surgery.

Synthetic opioids, including fentanyl, are now the most common drugs involved in drug overdose deaths in the United States. In 2017, 59 percent of opioid-related deaths involved fentanyl compared to 14.3 percent in 2010.  Some drug dealers are mixing fentanyl with other drugs, such as heroin, cocaine, methamphetamine, and MDMA. This is because it takes very little to produce a high with fentanyl, making it a cheaper option.

Table 8.9: Possible Health Effects of Heroin
Time Effects
Short-term Extreme happiness, drowsiness, nausea, confusion, constipation, sedation, problems breathing, unconsciousness.
Long-term Physical dependence, possible brain damage, withdrawal symptoms including: muscle and bone pain, sleep problems, diarrhea and vomiting, cold flashes with goose bumps, uncontrollable leg movements, and severe cravings.
Other Health-related Issues Life-threatening symptoms of Fentanyl overdose include:  slow/stop breathing, hypoxia, coma, brain damage, death.


Hallucinogens are a diverse group of drugs that alter a person’s awareness of their surroundings as well as their own thoughts and feelings.  They are commonly split into two categories: classic hallucinogens (such as LSD) and dissociative drugs (such as PCP). Both types of hallucinogens can cause hallucinations, or sensations and images that seem real though they are not. Additionally, dissociative drugs can cause users to feel out of control or disconnected from their body and environment. Common classic hallucinogens include: LSD,Psilocybin, Peyote, DMT, and 251-NBOMe. Common Dissociative hallucinogens include:  PCP, ketamine, DXM, and Salvia.

Table 8.10: Possible Health Effects of Hallucinogens
Time Effects
Short-term Increased heart rate, nausea, intensified feelings and sensory experiences, changes in sense of time, increased blood pressure, breathing rate, or body temperature, loss of appetite, dry mouth, sleep problems, spiritual experiences, feelings of relaxation, uncoordinated movements, excessive sweating, panic, paranoia—extreme and unreasonable distrust of others, psychosis—disordered thinking detached from reality, and bizarre behaviors.
Long-term Persistent psychosis, Hallucinogen Persisting Perception Disorder (HPPD), speech problems, memory loss, depression/suicide.
Other Health-related Issues Disrupt communication between brain chemical systems throughout the brain and spinal cord.  Large or prolonged doses of dissociative drugs, like PCP, can cause seizures, coma, or death. Unintentional injuries could be caused by doing things they wouldn’t do in real life, like jumping out of a window.
Drug Abuse or Addiction Treatment

Addiction is treatable and can be successfully managed, but the best is to prevent drug abuse in the first place.

As with most other chronic diseases, such as diabetes, asthma, or heart disease, treatment for drug addiction generally isn’t a cure.  Because addiction is a chronic disease, people can’t simply stop using drugs for a few days and be cured. Most patients need long-term or repeated care to stop using completely and recover their lives.

People who are recovering from an addiction will be at risk for relapse for years and possibly for their whole lives. Research shows that combining addiction treatment medicines with behavioral therapy ensures the best chance of success for most patients. Treatment approaches tailored to each patient’s drug use patterns and any co-occurring medical, mental, and social problems can lead to continued recovery.

More good news is that drug use and addiction are preventable. Results from NIDA-funded research have shown that prevention programs involving families, schools, communities, and the media are effective for preventing or reducing drug use and addiction. Although personal events and cultural factors affect drug use trends, when young people view drug use as harmful, they tend to decrease their drug taking. Therefore, education and outreach are key in helping people understand the possible risks of drug use. Teachers, parents, and health care providers have crucial roles in educating young people and preventing drug use and addiction.

Addiction treatment must help the person do the following:

  • Stop using drugs
  • Stay drug-free
  • Be productive in the family, at work, and in society

Based on scientific research since the mid-1970s, the following key principles should form the basis of any effective treatment program:

  • Addiction is a complex but treatable disease that affects brain function and behavior.
  • No single treatment is right for everyone.
  • People need to have quick access to treatment.
  • Effective treatment addresses all of the patient’s needs, not just his or her drug use.
  • Staying in treatment long enough is critical.
  • Counseling and other behavioral therapies are the most commonly used forms of treatment.
  • Medications are often an important part of treatment, especially when combined with behavioral therapies.
  • Treatment plans must be reviewed often and modified to fit the patient’s changing needs.
  • Treatment should address other possible mental disorders.
  • Medically assisted detoxification is only the first stage of treatment.
  • Treatment doesn’t need to be voluntary to be effective.
  • Drug use during treatment must be monitored continuously.
  • Treatment programs should test patients for HIV/AIDS, hepatitis B and C, tuberculosis, and other infectious diseases as well as teach them about steps they can take to reduce their risk of these illnesses.

Successful treatment has several steps:

  1. Detoxification (the process by which the body rids itself of a drug)
  2. Behavioral counseling
    • Behavioral therapies help patients modify their attitudes and behaviors related to drug use and increase healthy life skills. Patients can receive treatment in many different settings with various approaches.
    • Outpatient behavioral treatment includes a wide variety of programs for patients who visit a behavioral health counselor on a regular schedule. Most of the programs involve individual or group drug counseling, or both. These programs typically offer forms of behavioral therapy such as cognitive-behavioral therapy, multidimensional family therapy, and motivational incentives (contingency management). Treatment is sometimes intensive at first, where patients attend multiple outpatient sessions each week. After completing intensive treatment, patients transition to regular outpatient treatment, which meets less often and for fewer hours per week to help sustain their recovery.
    • Inpatient or residential treatment  can also be very effective, especially for those with more severe problems (including co-occurring disorders). Licensed residential treatment facilities offer 24-hour structured and intensive care, including safe housing and medical attention.
  3. Medication (for opioid, tobacco, or alcohol addiction)
    • Medications help suppress withdrawal symptoms during detoxification. Detoxification is not in itself “treatment,” but only the first step in the process. Patients who do not receive any further treatment after detoxification usually resume their drug use.
    • Patients can use medications to help re-establish normal brain function and decrease cravings to reduce the chances of a re-lapse. People who use more than one drug, which is very common, need treatment for all of the substances they use.
  4. Evaluation and treatment for co-occurring mental health issues such as depression and anxiety
  5. Long-term follow-up to prevent relapse

Behavioral Addiction

Substance and behavioral addictions are known as Addiction Disorders.  With substance addiction the person is physically addicted to a substance or drug, however with a behavioral addiction they are addicted to the positive physical and mental feelings associated with the behavior.  Both types of addiction impact a persons physical and mental health and both types of addiction have similar negative consequences.  Both addictions are characterized by a dependence on a substance or an activity[2].

Experts have identified six criteria to determine a behavioral addiction:

  1. Salience: Domination of a person’s life by the activity
  2. Euphoria: A ‘buzz’ or a ‘high’ is derived from the activity
  3. Tolerance: The activity has to be undertaken to a progressively greater extent to achieve the same ‘buzz’
  4. Withdrawal Symptoms: Cessation of the activity leads to the occurrence of unpleasant emotions or physical effects
  5. Conflict: The activity leads to conflict with others or self-conflict
  6. Relapse and Reinstatement: Resumption of the activity with the same vigor subsequent to attempts to abstain, negative life consequences, and negligence of job, educational or career opportunities.

Common Behavioral Addiction Disorders include gambling addiction, shopping addiction, and internet gaming addiction.

As with drug addiction, the best treatment for behavioral addiction is prevention.

Key Takeaways for Chapter 8

  • Drug addiction is a chronic disease characterized by compulsive, difficult to control drug seeking despite harmful consequences.
  • The  pleasurable “high” along with changes in the brain can lead to drug dependence and addiction.
  • Tolerance to a drug leads to increase use of the drug.
  • Withdrawal symptoms can be a sign of drug dependence.
  • No single factor can predict whether a person will become addicted to drugs.
  • Drug addiction is treatable and can be successfully managed.
  • Prevention is key.  Teachers, parents, and health care providers have crucial roles in educating young people and preventing drug use and addiction.

  1. Substance Abuse and Mental Health Services Administration. (2021). Key substance use and mental health indicators in the United States: Results from the 2020 National Survey on Drug Use and Health (HHS Publication No. PEP21-07-01-003, NSDUH Series H-56). Rockville, MD: Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration. Retrieved from
  2. Alavi, S. S., Ferdosi, M., Jannatifard, F., Eslami, M., Alaghemandan, H., & Setare, M. (2012). Behavioral Addiction versus Substance Addiction: Correspondence of Psychiatric and Psychological Views. International journal of preventive medicine, 3(4), 290–294.


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