Difficulty: Introductory | Prerequisites: Read the Consciousness and Sleep notes first. You will need the idea that consciousness exists on a continuum and can be altered by both internal and external factors.
This section picks up where the consciousness material leaves off. Where sleep is a naturally occurring altered state, psychoactive drugs, hypnosis, and meditation are ways consciousness gets shifted through external substances or deliberate practices. This matters because drug use, addiction, and altered states come up repeatedly in abnormal psychology, health psychology, and neuroscience topics later in the course. The material also has obvious real-world relevance: understanding tolerance, dependence, and the mechanisms behind different drug categories helps you make sense of public health issues and clinical treatment approaches.
Psychoactive drugs alter consciousness by acting on the nervous system, and they fall into three broad categories: depressants, stimulants, and hallucinogens. Repeated use can produce tolerance, physical dependence, and psychological dependence. Hypnosis and meditation are non-chemical routes to altered consciousness, and psychologists disagree about whether hypnosis is a genuinely distinct state or a form of social role-playing.
Psychoactive drugs
Drugs that act on the nervous system to alter consciousness, modify perception, and change mood. In simple terms, any substance that changes how you think, feel, or perceive the world.
Tolerance
The need to take increasing amounts of a drug to get the same effect. Think of it as the body adapting to the substance so that the original dose no longer does the job.
Physical dependence
The physiological need for a drug that causes unpleasant withdrawal symptoms, such as physical pain and craving, when the drug is discontinued. This is the body saying it cannot function normally without the substance.
Psychological dependence
The strong desire to repeat the use of a drug for emotional reasons, such as a feeling of well-being and reduction of stress. The body may not need the drug, but the person feels they do.
Addiction
Either a physical or a psychological dependence, or both, on a drug. In simple terms, it is the state where a person's drug use has become compulsive and difficult to stop.
Depressants
Psychoactive drugs that slow down mental and physical activity. Alcohol is the most widely used depressant.
Alcoholism
A disorder involving long-term, repeated, uncontrolled, compulsive, and excessive use of alcoholic beverages, associated with impairment of the drinker's health and social relationships. This is a clinical pattern, not simply drinking a lot.
Tranquilisers
Depressant drugs, such as Valium and Xanax, that reduce anxiety and induce relaxation. These are also called anxiolytics (anxiety-dissolving drugs) in clinical settings.
Barbiturates
Depressant drugs, such as Nembutal and Seconal, that decrease central nervous system activity. They were once widely prescribed for sleep and anxiety but carry a high risk of overdose.
Stimulants
Psychoactive drugs that increase the central nervous system's activity. This category includes caffeine, nicotine, amphetamines, and cocaine.
Hallucinogens
Psychoactive drugs that modify a person's perceptual experiences and produce visual images that are not real. LSD, psilocybin (magic mushrooms), and mescaline are common examples.
Hypnosis
An altered state of consciousness, or a psychological state of altered attention and expectation, in which the individual is unusually receptive to suggestions. Whether it is a "real" altered state is debated.
Divided consciousness view of hypnosis
Hilgard's view that hypnosis involves a splitting of consciousness into two separate components: one that follows the hypnotist's commands and another that acts as a "hidden observer." Think of it as two tracks of awareness running in parallel.
Social cognitive behaviour view of hypnosis
The perspective that hypnosis is a normal state in which the hypnotised person behaves the way they believe a hypnotised person should behave. In simple terms, hypnosis works through social expectation and role-playing rather than a special trance state.
Meditation
The attainment of a peaceful state of mind in which thoughts are not occupied by worry; the meditator is mindfully present to thoughts and feelings but is not consumed by them. Think of it as deliberate, practised mental stillness.
There are three main categories, organised by their primary effect on the central nervous system:
Depressants slow down CNS activity.
Alcohol is the most common. It impairs judgement, slows reaction time, and at high doses can suppress vital functions.
Tranquilisers (e.g. Valium, Xanax) reduce anxiety. They are prescribed clinically but carry dependence risk.
Barbiturates (e.g. Nembutal, Seconal) were once standard treatments for insomnia and anxiety. They have largely been replaced by safer alternatives because the margin between a therapeutic dose and a lethal dose is narrow.
Stimulants speed up CNS activity.
Caffeine and nicotine are the most widely used stimulants globally.
Amphetamines and cocaine produce intense but short-lived euphoria by increasing dopamine activity.
Stimulants can cause increased heart rate, elevated blood pressure, and, with chronic use, serious cardiovascular problems.
Hallucinogens distort perception and can produce sensory experiences without real external stimuli.
LSD, psilocybin, and mescaline are classic examples.
Effects are highly variable and influenced by the user's mindset and environment (sometimes called "set and setting").
Tolerance develops as the body adjusts to a substance. The same dose produces a weaker effect over time, prompting higher doses.
Physical dependence means the body has adapted to the drug's presence. Removal triggers withdrawal symptoms (pain, nausea, tremors, seizures, depending on the substance).
Psychological dependence centres on emotional need rather than physiological adaptation. A person may crave the drug to cope with stress or to recreate a feeling of well-being, even if withdrawal symptoms are mild or absent.
Addiction is the umbrella term covering either or both forms of dependence. It is characterised by compulsive use despite negative consequences.
Hypnosis involves an altered state of attention and heightened suggestibility.
Two competing views explain it:
Hilgard's divided consciousness view: Consciousness splits into two streams during hypnosis. One stream responds to the hypnotist's suggestions; the other, the "hidden observer," remains aware of what is happening. This view treats hypnosis as a genuinely distinct state of consciousness.
Social cognitive behaviour view: Hypnosis is not a special state at all. The person is simply enacting the role they believe a hypnotised person should play, influenced by social expectations and context. This view treats hypnosis as a product of normal social cognition.
In practice, hypnosis has been used for pain management, smoking cessation, and anxiety reduction. Its effectiveness varies significantly between individuals.
Meditation is a voluntary practice aimed at achieving a calm, focused state of awareness.
It does not eliminate thoughts; rather, it changes the practitioner's relationship to their thoughts, so they observe without being swept up.
Research links regular meditation to reduced stress, lower blood pressure, and improved attention. These effects connect to health psychology topics covered later in most introductory courses.
Understanding tolerance and dependence is central to clinical treatment of substance use disorders, including determining withdrawal protocols and relapse prevention strategies. The distinction between physical and psychological dependence also matters in debates about drug scheduling and public policy. Hypnosis has documented clinical utility for pain management in medical settings, and meditation-based interventions (such as mindfulness-based stress reduction) are now standard components of cognitive-behavioural therapy programmes.
Students often think tolerance and dependence are the same thing. Tolerance is about needing more of the drug for the same effect. Dependence is about what happens when you stop taking it.
Many students assume all addiction involves physical dependence. Psychological dependence alone can sustain addictive behaviour, even without withdrawal symptoms.
Hypnosis is frequently misunderstood as mind control. Neither major theory supports this. In the divided consciousness view, part of the mind remains aware; in the social cognitive view, the person is cooperating voluntarily.
Students sometimes treat "depressant" as meaning "causes depression." Depressants slow CNS activity, which is a pharmacological description, not a mood description (though prolonged alcohol abuse can contribute to depressive symptoms).
⚠️ Be able to classify specific drugs into the correct category (depressant, stimulant, hallucinogen) and give examples for each.
⚠️ Know the distinction between physical dependence and psychological dependence, and be ready to explain how each relates to addiction.
⚠️ Expect a comparison question on the two views of hypnosis (Hilgard's divided consciousness vs. social cognitive behaviour). Know the key claim and the main evidence for each.
⚠️ Tolerance is a frequent short-answer or multiple-choice target. Be clear on the definition: needing more of the drug for the same effect.
⚠️ Understand where meditation fits on the consciousness spectrum and what research says about its benefits.
True or False: Barbiturates are a type of stimulant. (False, they are depressants.)
__________ is the need to take increasing amounts of a drug to achieve the same effect. (Tolerance)
True or False: The social cognitive behaviour view of hypnosis holds that consciousness splits into two streams. (False, that is Hilgard's divided consciousness view.)
Psychological dependence is driven by __________ needs, while physical dependence is driven by __________ adaptation. (emotional; physiological)
True or False: Meditation aims to stop all thoughts entirely. (False, it changes one's relationship to thoughts rather than eliminating them.)
Q: What are the three main categories of psychoactive drugs, and how does each affect the central nervous system?
A: Depressants slow down CNS activity (e.g. alcohol, tranquilisers, barbiturates). Stimulants speed up CNS activity (e.g. caffeine, nicotine, amphetamines, cocaine). Hallucinogens distort perceptual experiences and can produce sensory experiences without real external stimuli (e.g. LSD, psilocybin).
Q: Explain the difference between physical dependence and psychological dependence.
A: Physical dependence is the body's physiological adaptation to a drug, producing withdrawal symptoms (pain, nausea, tremors) when the drug is discontinued. Psychological dependence is the emotional desire to repeat drug use for feelings of well-being or stress reduction, without necessarily involving physiological withdrawal.
Q: Compare Hilgard's divided consciousness view and the social cognitive behaviour view of hypnosis.
A: Hilgard argued that hypnosis splits consciousness into two streams: one that responds to suggestions and a "hidden observer" that remains aware. This treats hypnosis as a genuine altered state. The social cognitive behaviour view holds that hypnosis is not a special state; instead, the person behaves as they believe a hypnotised person should, driven by social expectations and role-playing.
Q: What is tolerance, and how does it relate to the risk of overdose?
A: Tolerance is the body's adaptation to a drug such that increasing amounts are needed for the same effect. This raises overdose risk because the person escalates their dose to overcome tolerance, potentially reaching dangerous or lethal levels.
Q: How does meditation differ from other altered states of consciousness discussed in this chapter?
A: Meditation is a voluntary, practised state in which the person remains aware but relates to their thoughts without being consumed by them. Unlike sleep, it does not involve loss of consciousness. Unlike drug-induced states, it does not depend on external substances. Unlike hypnosis, it does not involve heightened suggestibility to another person's directions.
Drug tolerance and dependence connect directly to later material on substance use disorders in abnormal psychology, including clinical criteria for diagnosis. The neuroscience of how stimulants and depressants act on neurotransmitter systems (particularly dopamine and GABA) ties back to the biological psychology chapter. Meditation and hypnosis link forward to therapeutic techniques covered in the treatment chapter, especially mindfulness-based cognitive therapy and clinical hypnotherapy.
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