Premed · Premed · Introductory Psychology
Lecture 8: States of Consciousness: Drugs and Altered States
Introductory Psychology
Learning Objectives
By the end of this lecture, students will be able to:
- Define psychoactive drugs and explain the concepts of tolerance, dependence, and withdrawal
- Classify the major categories of psychoactive drugs and describe their effects
- Explain how drugs affect neurotransmitter systems at the synapse
- Discuss hypnosis and its psychological explanations
- Describe the effects of meditation on consciousness and well-being
Lecture Content
I. Psychoactive Drugs: Basic Concepts
A psychoactive drug is any chemical substance that alters perception, mood, cognition, or behavior by acting on the nervous system. Understanding how these drugs work requires familiarity with several pharmacological concepts. An agonist is a drug that mimics or enhances a neurotransmitter's effect, while an antagonist blocks or reduces it. A reuptake inhibitor prevents a neurotransmitter from being reabsorbed by the presynaptic neuron, thereby increasing its availability in the synapse.
With repeated use of a psychoactive drug, tolerance develops: the brain makes compensatory adjustments (neuroadaptation) so that larger doses are needed to achieve the same effect. Physical dependence occurs when the body has adapted to a drug to such a degree that withdrawal symptoms appear when use is discontinued. These withdrawal symptoms are typically opposite to the drug's effects. Psychological dependence involves craving and compulsive drug-seeking behavior. Addiction, now formally termed substance use disorder in the DSM-5, is characterized by compulsive drug use despite negative consequences and is assessed through criteria including impaired control, social impairment, risky use, and pharmacological indicators.
II. Depressants
Depressants are drugs that slow neural activity and reduce bodily functions. Alcohol (ethanol) is the most widely used depressant. It enhances GABA (inhibitory) activity while inhibiting glutamate (excitatory) activity. At low doses, alcohol reduces inhibition and produces relaxation along with impaired judgment. At high doses, it causes slurred speech, motor impairment, memory blackouts, and respiratory depression. Chronic use leads to liver disease, brain damage, and Korsakoff's syndrome, a condition caused by thiamine deficiency that produces severe memory loss. The concept of alcohol myopia explains how intoxication narrows attention to the most salient cues in the environment. Prenatal alcohol exposure can cause fetal alcohol spectrum disorders (FASD), characterized by intellectual disability and distinctive facial abnormalities.
Barbiturates such as phenobarbital and secobarbital enhance GABA activity and were historically used as sedatives and anti-anxiety medications. They are highly addictive and dangerous in overdose due to respiratory depression, and have been largely replaced by benzodiazepines. Benzodiazepines — including diazepam (Valium), alprazolam (Xanax), and lorazepam (Ativan) — also enhance GABA activity but at a different receptor site, making them somewhat safer. They are used for anxiety, insomnia, and seizures, though they still carry a risk of dependence.
Opioids, including morphine, heroin, oxycodone, and fentanyl, bind to endorphin receptors (specifically mu-opioid receptors), producing euphoria, pain relief, and sedation. They are highly addictive and carry a significant risk of fatal respiratory depression in overdose. Naloxone (Narcan), an opioid antagonist, can reverse overdose. The widespread misuse of opioids has created a major public health crisis.
<image>A diagram showing how different depressant drugs act at the synapse. Panel A: Normal synaptic transmission with GABA released from the presynaptic neuron binding to GABA-A receptors on the postsynaptic neuron. Panel B: Alcohol and benzodiazepines binding to different sites on the GABA-A receptor complex, each enhancing the inhibitory effect of GABA (chloride channel opens wider). Panel C: Opioids binding to mu-opioid receptors on the postsynaptic neuron, mimicking endorphins. Panel D: A dose-response curve showing escalating effects of alcohol from disinhibition at low doses to unconsciousness and death at high doses.</image>
III. Stimulants
Stimulants speed up neural activity and increase arousal. Caffeine, the world's most widely consumed psychoactive substance, works by blocking adenosine receptors; since adenosine normally promotes drowsiness, blocking it increases alertness and reduces fatigue. Mild physical dependence is possible, with headaches being the most common withdrawal symptom. Nicotine activates acetylcholine (nicotinic) receptors and triggers dopamine release in the brain's reward pathways. It is highly addictive and tolerance develops rapidly. Paradoxically, nicotine can be both stimulating and relaxing depending on the context and dose.
Cocaine blocks the reuptake of dopamine, serotonin, and norepinephrine, producing an intense but short-lived euphoria followed by a crash characterized by dysphoria and fatigue. It is highly addictive and carries risks of cardiac arrest, stroke, and psychosis. Amphetamines and methamphetamine increase the release and block the reuptake of dopamine and norepinephrine, boosting energy, alertness, and confidence while suppressing appetite. Chronic use can produce neurotoxicity, paranoia, psychosis, and dental damage known colloquially as "meth mouth."
MDMA (ecstasy or molly) increases the release of serotonin, dopamine, and norepinephrine, producing feelings of euphoria, emotional warmth, and empathy. Risks include hyperthermia, dehydration, serotonin syndrome, and potential neurotoxicity. MDMA-assisted psychotherapy is currently being investigated as a treatment for PTSD.
IV. Hallucinogens
Hallucinogens distort perceptions, thoughts, and emotions. LSD (lysergic acid diethylamide) acts primarily on serotonin receptors, particularly 5-HT2A receptors, producing vivid hallucinations, synesthesia, altered sense of time, and mystical experiences. It is not physically addictive and no lethal overdose has been reported, though "bad trips" involving intense anxiety or paranoia can occur, and rare cases of persistent perceptual changes (HPPD) have been documented. Psilocybin, the active compound in magic mushrooms, acts on the same serotonin receptors and produces similar but shorter-lasting effects. Research suggests it may have therapeutic benefits for depression, end-of-life anxiety, and addiction. Mescaline, derived from the peyote cactus, is another serotonergic hallucinogen with deep cultural and spiritual significance.
Cannabis (marijuana) occupies an unusual position in drug classification, sometimes categorized as a mild hallucinogen, sometimes as a depressant, and sometimes placed in its own category. Its primary active ingredient, THC (delta-9-tetrahydrocannabinol), acts on the endocannabinoid system through CB1 and CB2 receptors, producing relaxation, euphoria, altered time perception, and increased appetite, with mild hallucinations possible at high doses. Risks include impaired memory and learning (especially in adolescents), a possible link to psychosis in vulnerable individuals, and debated effects on motivation. Medical applications include treatment of pain, nausea, epilepsy, and appetite loss.
Dissociative drugs such as ketamine and PCP block NMDA glutamate receptors, producing feelings of detachment from the body and environment. Ketamine is currently being investigated as a rapid-acting antidepressant.
<image>A chart categorizing psychoactive drugs by their effects on the central nervous system. Three columns labeled "Depressants," "Stimulants," and "Hallucinogens." Each column lists the drugs in that category, their primary neurotransmitter mechanisms (with small synapse diagrams), typical psychological effects, and risk profiles. Arrows at the bottom show a spectrum from CNS depression on the left to CNS excitation in the middle to perceptual distortion on the right. Cannabis is placed between categories with dotted lines indicating its mixed classification.</image>
V. Hypnosis
Hypnosis is a social interaction in which a hypnotist suggests that a subject will experience changes in sensations, perceptions, thoughts, or behavior. Hypnotic induction typically involves focused attention, relaxation, and openness to suggestion. Research supports the effectiveness of hypnosis for reducing pain (hypnotic analgesia) and for altering perceptions and behaviors in suggestible individuals. It can also assist in some therapeutic contexts, including habit change and anxiety reduction. However, hypnosis cannot reliably force people to act against their will, produce superhuman abilities, or enhance memory — indeed, hypnotically "recovered" memories are often false.
Two major theories attempt to explain hypnosis. Hilgard's dissociation theory proposes that hypnosis splits consciousness into two simultaneous streams: one that follows the hypnotic suggestions and a "hidden observer" that remains aware of what is happening. The social-cognitive theory, advanced by Barber and Spanos, argues that hypnotic effects result from the subject's expectations, motivation, and role-playing rather than from a genuinely altered state of consciousness. The modern view is that hypnosis likely involves both genuine changes in brain processing and social-cognitive factors. Hypnotic susceptibility varies widely among individuals, with about 15-20% of people being highly hypnotizable.
VI. Meditation
Meditation encompasses a set of practices that train attention and awareness to achieve mental clarity, calmness, and emotional balance. Focused attention (concentrative) meditation involves sustaining attention on a single object, breath, or mantra. Open monitoring (mindfulness) meditation cultivates non-reactive awareness of present-moment thoughts, sensations, and feelings. Loving-kindness (metta) meditation is directed toward cultivating feelings of compassion and goodwill.
Physiologically, meditation is associated with decreased heart rate, blood pressure, and cortisol levels, along with increased alpha and theta brain wave activity. Long-term practitioners show structural brain changes including increased cortical thickness in the prefrontal cortex and insula and increased gray matter in the hippocampus. Psychologically, research supports benefits including reduced stress, anxiety, and depression symptoms, improved attention and emotional regulation, enhanced well-being, and stronger immune function. That said, effect sizes vary, some studies have methodological limitations, and meditation should not be regarded as a cure-all.
