Question
Classify commonly abused drugs based on their effect on the body. What is the mechanism of drug addiction, and what are the effects of alcohol abuse on the body?
(NEET + CBSE Class 12)
Solution — Step by Step
| Category | Effect on body | Examples |
|---|---|---|
| Opioids (narcotics) | Pain relief, sedation, euphoria | Morphine, heroin, codeine |
| Stimulants | Increase alertness, energy | Cocaine, amphetamines, caffeine |
| Depressants | Slow brain activity, relaxation | Alcohol, barbiturates, benzodiazepines |
| Hallucinogens | Alter perception, hallucinations | LSD, cannabis (at high doses) |
| Cannabinoids | Altered mood, relaxation | Marijuana (from Cannabis sativa) |
Most abused drugs affect the brain’s reward pathway (mesolimbic dopamine system):
- Drug intake causes a surge of dopamine in the brain
- This creates intense pleasure (the “high”)
- With repeated use, the brain reduces its own dopamine production (tolerance)
- More drug is needed for the same effect
- Without the drug, dopamine levels crash — causing withdrawal symptoms (anxiety, tremors, nausea)
- This cycle of tolerance and withdrawal drives dependence (addiction)
Opioids bind to specific receptors in the brain (opioid receptors) that normally respond to endorphins — the body’s natural painkillers.
| System | Effect |
|---|---|
| Liver | Fatty liver to cirrhosis (irreversible scarring) |
| Nervous system | Impaired coordination, memory loss, neuropathy |
| Stomach | Gastritis, ulcers |
| Heart | Cardiomyopathy, high blood pressure |
| Social | Family disruption, accidents, violence |
| Immune | Weakened immunity, more susceptible to infections |
Drug Classification Tree by Action
flowchart TD
A["Commonly Abused Drugs"] --> B["Opioids — pain suppression"]
A --> C["Stimulants — increase activity"]
A --> D["Depressants — decrease activity"]
A --> E["Hallucinogens — alter perception"]
A --> F["Cannabinoids — mood alteration"]
B --> B1["Morphine, Heroin"]
B --> B2["Bind opioid receptors"]
C --> C1["Cocaine, Amphetamines"]
C --> C2["Increase dopamine release"]
D --> D1["Alcohol, Barbiturates"]
D --> D2["Enhance GABA activity"]
E --> E1["LSD"]
F --> F1["Marijuana — Cannabis sativa"]Why This Works
Drug classification by effect makes clinical and exam sense. Each category affects the nervous system differently — opioids suppress pain signals, stimulants enhance alertness, depressants slow neural activity. Understanding the mechanism (dopamine pathway) explains why all these different drugs can cause addiction through the same reward circuit.
Common Mistake
Students confuse dependence with tolerance. Tolerance means the body needs increasing doses for the same effect (the receptors become less sensitive). Dependence means the body cannot function normally without the drug (withdrawal symptoms appear). A person develops tolerance first, then dependence. NEET specifically tests this distinction.