Difficulty: Introductory | Prerequisites: Basic understanding of the nervous system
This topic covers why people use psychoactive substances, how addiction develops as a chronic condition, and what treatment looks like. It connects to the broader course themes of how biological processes and learning shape behaviour. If you have not reviewed the basics of how neurotransmitters work, do that first.
People use drugs for a range of reasons: stress relief, peer pressure, genetic vulnerability, and the way substances interact with the nervous system. Addiction is classified as a chronic disease, not a moral failing, which means it requires sustained treatment rather than a short detox. Psychologists play a central role in treatment through psychotherapy, motivation building, and relapse prevention.
Physiological drug dependence
A state in which the body has become so accustomed to functioning with a drug present that it cannot operate normally without it. In simple terms, the body has adapted to the drug and now needs it just to feel "normal."
Addiction
A chronic, relapsing condition characterised by compulsive drug seeking and use despite harmful consequences. Think of it as the point where use has shifted from a choice to a compulsion driven by changes in brain chemistry.
Tolerance
The need for increasingly larger doses of a substance to achieve the same effect. In simple terms, the body gets used to the drug, so the original dose stops working as well.
Withdrawal
The set of physical and psychological symptoms that occur when a person stops taking a substance they are dependent on. These can range from mild discomfort to life-threatening reactions, depending on the substance.
Psychoactive substance
Any chemical that alters brain function, resulting in changes to perception, mood, consciousness, or behaviour. This includes illegal drugs, alcohol, caffeine, and nicotine.
Psychotherapy (in addiction treatment)
Talk-based therapy used to strengthen a patient's motivation, improve coping and problem-solving skills, and address the psychological dimensions of addiction. Think of it as the part of treatment that works on the mind, alongside any medical intervention that works on the body.
Drug use peaks in the late teens and 20s. According to the National Institute on Drug Abuse, more than a fifth of 18- to 25-year-olds have used an illegal substance in the past month.
Peer relationships are a major factor, particularly for teenagers, who are more vulnerable to social pressure and less equipped to assess long-term risk.
Genetic predisposition plays a role. Hundreds of genes in a person's DNA may amplify the risk of developing an alcohol or substance use disorder.
Stress relief is a common motivator. Alcohol and other substances can temporarily reduce stress and redirect attention, but the underlying problems remain once the effects wear off.
Drugs affect the nervous system in different ways, which is why effects vary widely between substances and between individuals.
Addiction begins with voluntary use but progresses as the substance changes brain chemistry.
Physiological dependence develops when the body adapts to the drug's presence and cannot function normally without it. The person feels they need the substance to cope with daily life.
Tolerance builds over time: the same dose produces a diminishing effect, driving the person to increase their intake.
Everyday substances count. Caffeine (in coffee) and nicotine (in cigarettes) have addictive properties, even though people do not typically classify them alongside heroin or alcohol (Li, Volkow, and Baler, 2007).
Addiction is a chronic disease. Patients cannot simply stop for a few days and be cured. Most require long-term or repeated care.
Research shows that about one-third of people treated for alcohol problems have no further symptoms one year later. Many others substantially reduce their drinking and report fewer related problems.
Psychotherapy helps by strengthening motivation, building problem-solving and coping skills, and setting achievable short-term goals.
Therapists specialising in addiction recovery help patients work through the psychological dimensions of dependence, including stress management and relapse prevention.
Treatment effectiveness depends partly on the individual's willingness to engage and on whether they continue using during treatment.
The concept of physiological dependence applies to substances most people use daily without thinking of them as drugs. A person who drinks coffee every morning and gets headaches when they skip it is experiencing mild withdrawal from caffeine. Understanding this helps normalise the concept of dependence and removes the stigma that addiction only happens to "other people."
In clinical practice, psychologists working in addiction recovery use techniques like cognitive-behavioural therapy and motivational interviewing to help patients build the skills they need to manage cravings, handle stress, and avoid relapse.
Students often think addiction is a choice or a sign of weak willpower. It is classified as a chronic disease involving changes to brain chemistry. Willpower alone is not sufficient to overcome it.
A common error is assuming treatment means a short detox period. Addiction typically requires long-term or repeated care, much like managing diabetes or hypertension.
Students sometimes believe that "everyday" substances like caffeine and nicotine are not really addictive. They are. They produce tolerance, dependence, and withdrawal, just at a lower intensity than substances like heroin.
Another misconception is that treatment either works completely or fails completely. In practice, many patients substantially reduce their use and experience fewer related problems, even if they do not achieve total abstinence immediately.
Know the definition of physiological dependence and be able to distinguish it from psychological dependence. Exam questions often present a scenario and ask you to identify which type is at play.
Be able to explain why addiction is classified as a chronic disease, not a behavioural choice.
Understand the risk factors for substance use: peer pressure, genetics, stress, and age of first use.
Know that caffeine and nicotine are addictive substances (Li, Volkow, and Baler, 2007). This is a commonly tested point because students underestimate everyday drugs.
Be prepared to describe the psychologist's role in addiction treatment: psychotherapy, motivation strengthening, coping skills, and relapse prevention.
True or false: Addiction is best understood as a moral failing rather than a chronic disease. (False. It is classified as a chronic disease involving changes in brain chemistry.)
Fill in the blank: The body's need for increasingly larger doses to achieve the same effect is called ______. (Tolerance.)
True or false: Caffeine and nicotine are not considered addictive substances. (False. Both produce tolerance, dependence, and withdrawal.)
Fill in the blank: In ______ drug dependence, the body cannot function normally without the substance. (Physiological.)
True or false: About one-third of people treated for alcohol problems show no further symptoms one year later. (True.)
Q: Why do people use drugs, and what factors increase the risk of addiction?
A: People use drugs for stress relief, social pressure, curiosity, and because substances interact with the nervous system to produce pleasurable or numbing effects. Risk factors include peer relationships (especially in teenagers), genetic predisposition (hundreds of genes can amplify vulnerability), age of first use (peaks in late teens and 20s), and environmental stressors.
Q: Why is it difficult to treat drug abuse?
A: Addiction is a chronic disease that changes brain chemistry. Patients cannot simply stop for a few days and recover. Most require long-term or repeated care. Relapse is common and is considered part of the disease process, not a sign of treatment failure.
Q: What role might a psychologist take in a drug treatment programme?
A: Psychologists use psychotherapy to strengthen patients' motivation, improve problem-solving and stress reduction skills, set achievable short-term goals, and develop coping strategies. They address the psychological dimensions of dependence alongside any medical treatment for the physical dimensions.
Q: How does the example of caffeine dependence illustrate physiological drug dependence?
A: A person who drinks coffee every morning develops tolerance (needing more coffee for the same effect) and dependence (the body expects the caffeine). If they skip their coffee, they may experience withdrawal symptoms such as headaches and fatigue. This shows that physiological dependence is not limited to illegal substances.
This material connects directly to classical conditioning (covered in the next set of notes). Lauren's coffee dependence is both a physiological dependence example and a classical conditioning example, where the doorbell becomes a conditioned stimulus. It also connects to perception: substances alter how the nervous system processes sensory information, which links back to the earlier material on how perception is constructed rather than passively received. In the broader field, addiction research sits at the intersection of neuroscience, clinical psychology, and public health.
Drug use, addiction, substance use disorder, physiological dependence, psychological dependence, tolerance, withdrawal, psychoactive substances, caffeine addiction, nicotine addiction, alcohol use disorder, psychotherapy, addiction treatment, relapse prevention, chronic disease model of addiction, peer pressure, genetic risk factors, National Institute on Drug Abuse, Li Volkow Baler 2007, PSY II, Psychology II, FIU