AP Syllabus focus:
‘Stimulants, depressants, hallucinogens, and opioids have different effects, and repeated use can lead to tolerance, addiction, and withdrawal.’
Psychoactive drugs are commonly grouped by their overall effects on the central nervous system.
This diagram groups psychoactive drugs into major effect-based categories (stimulants, depressants, and hallucinogens) and visually shows where certain substances overlap across categories. It reinforces the AP Psych idea that drug “categories” summarize dominant effects, but real drugs can have mixed profiles depending on mechanisms and dose. Source
In AP Psychology, you should compare major categories and explain how repeated use can produce tolerance, addiction, and withdrawal.
Major drug categories (core effects)
Stimulants
Stimulants increase central nervous system activity, typically raising alertness and energy while reducing fatigue.
Common effects: increased heart rate, heightened arousal, talkativeness, decreased appetite
Risks with high dose or chronic use: anxiety, insomnia, cardiovascular strain, crash (fatigue/irritability)
Examples students often encounter: caffeine, nicotine, cocaine, amphetamines
Depressants
Depressants reduce central nervous system activity, often producing relaxation and lowered inhibitions.
Common effects: slowed reaction time, impaired judgement/coordination, drowsiness
Higher doses can suppress breathing and other vital functions (especially dangerous when combined with other depressants)
Examples: alcohol, barbiturates, benzodiazepines
Hallucinogens
Hallucinogens produce perceptual distortions and altered consciousness; experiences vary widely depending on dose, setting, and expectations.
Common effects: changes in sensory experience, time perception, mood, and thought patterns
Potential risks: panic reactions (“bad trips”), impaired judgement, accidents; some users experience lingering perceptual effects
Examples: LSD; many courses also discuss cannabis-related perceptual and cognitive changes in this broad context
Opioids
Opioids (narcotics) primarily reduce pain and can produce intense pleasure/euphoria.
Common effects: analgesia, relaxation, slowed breathing, sedation
High addiction potential; overdose risk is strongly linked to respiratory depression
This diagram summarizes multiple ways opioids impair breathing, including slowed and irregular respiration and reduced responsiveness to rising CO and falling O. It helps connect the clinical concept of opioid overdose to a concrete physiological mechanism: depressed brainstem-driven ventilation. Source
Examples: morphine, heroin, oxycodone, fentanyl
Tolerance, withdrawal, and addiction
Tolerance (why the same dose stops “working”)
Repeated drug use can produce tolerance, meaning more of the substance is needed to achieve the same effect.
This figure illustrates graded dose–response curves, which plot drug dose (x-axis) against magnitude of effect (y-axis). In the context of tolerance, students often conceptualize decreased sensitivity as needing a higher dose to reach the same effect level (a rightward shift of the curve), matching the definition that “more is needed” after repeated use. Source
Tolerance: Reduced responsiveness to a drug after repeated use, leading to the need for larger doses to achieve the same effect.
Tolerance can develop through learned (behavioral) factors and through physiological adaptation. Tolerance is drug- and context-specific; a person may show strong tolerance in familiar settings but less in unfamiliar ones, increasing overdose risk.
Withdrawal (what happens when use stops)
When a tolerated drug is reduced or stopped, the body may show withdrawal, often involving effects opposite to intoxication (e.g., agitation after depressants).
Withdrawal: Physical and psychological symptoms that occur when a person reduces or stops using a drug after developing tolerance or dependence.
Withdrawal severity depends on the drug category, dose, duration of use, and individual vulnerability. Depressants and opioids are especially associated with clinically significant withdrawal patterns.
Addiction (compulsion despite harm)
Addiction is marked by compulsive drug seeking and use even when it causes significant problems.
Key features emphasised in AP Psych: craving, loss of control, continued use despite negative consequences, and relapse risk
Addiction is supported by learning processes (reinforcement), cues and triggers, and neuroadaptation that makes non-drug rewards less motivating over time
Dependence and patterns of harm
Physical dependence refers to bodily adaptation (tolerance and withdrawal are central signs).
Psychological dependence refers to perceived need for the drug to cope, feel normal, or function.
Drugs differ in typical risk profiles:
Opioids: high overdose and addiction risk
Depressants: dangerous impairment and potentially severe withdrawal; mixing substances increases risk sharply
Stimulants: strong reinforcement and binge-crash cycles; health and mood disruption
Hallucinogens: less typical physical dependence but can create dangerous impairment and acute anxiety/panic reactions
FAQ
Tolerance may develop unevenly across effects.
A person might tolerate euphoric effects more than respiratory depression.
Tolerance can be context-dependent; using in a new environment can reduce tolerance and make a typical dose dangerous.
Cross-tolerance occurs when tolerance to one drug reduces sensitivity to another with similar effects.
This matters because alcohol and some sedatives can share depressant effects, leading people to take more than intended and dangerously compound impairment.
Withdrawal reflects the body “rebounding” after adaptation.
If a drug repeatedly pushed the nervous system in one direction, the body may compensate in the other direction; removing the drug reveals that compensatory state.
Opioids can slow breathing directly, and high doses can cause respiratory arrest.
Potency differences and contamination (e.g., fentanyl) also make dose estimation difficult, raising accidental overdose risk.
Ending withdrawal does not erase learned associations.
Conditioned cues (people, places, stress) can trigger craving and habitual seeking, and long-term changes in motivation can make relapse more likely without ongoing support.
Practice Questions
Describe two differences between stimulants and depressants. (3 marks)
1 mark: stimulant increases CNS activity/arousal (e.g., alertness, heart rate).
1 mark: depressant decreases CNS activity (e.g., slowed reactions, sedation).
1 mark: accurate comparative consequence (e.g., stimulants can cause insomnia/anxiety; depressants impair coordination/judgement or suppress breathing at high dose).
Explain how repeated use of an opioid can lead to tolerance, withdrawal, and addiction. (6 marks)
1 mark: tolerance defined/applied (needs more for same analgesia/euphoria).
1 mark: neuroadaptation/body adjusts with repeated use (general explanation).
1 mark: withdrawal described when stopping/reducing (e.g., distressing symptoms).
1 mark: link between tolerance/withdrawal and continued use (negative reinforcement).
1 mark: addiction described as compulsive use despite harm.
1 mark: relapse/craving or cue-triggered use included as maintaining factor.
