BiologyCBSE Class 12 · Human Health and Disease

Drugs and Alcohol Abuse

Updated 15 October 2026 · Fact-checked

Commonly abused drugs are opioids (heroin from the poppy), cannabinoids (marijuana, hashish, charas, ganja from Cannabis) and coca alkaloids (cocaine from Erythroxylum coca). Tobacco's nicotine raises blood pressure and heart rate. Repeated use raises tolerance, leading to addiction and dependence with withdrawal symptoms. Education, counselling, family support and professional help prevent and control abuse.

Follow each row from plant to drug to effect: heroin depresses, cocaine stimulates, and repeated use builds tolerance and addiction.

Illustration drawn for QuestionBuddy.

Understand Drugs and Alcohol Abuse

Commonly abused drugs. Most come from flowering plants, some from fungi.

Group	Source	Example	How taken	Action
Opioids	latex of poppy, Papaver somniferum	heroin ('smack', diacetylmorphine), made by acetylation of morphine	snorting, injection	bind opioid receptors in the CNS and gut; heroin is a depressant that slows body functions
Cannabinoids	inflorescences, leaves, resin of Cannabis sativa	marijuana, hashish, charas, ganja	inhalation, oral	act on cannabinoid receptors mainly in the brain; affect the cardiovascular system
Coca alkaloids	coca plant, Erythroxylum coca (South America)	cocaine ('coke', 'crack')	usually snorted	interferes with transport of dopamine; strong CNS stimulant: euphoria, more energy; excess causes hallucinations

Other plants with hallucinogenic properties: *Atropa belladonna* and *Datura*. Medicines such as barbiturates, amphetamines and benzodiazepines, normally used to help patients cope with mental illnesses like depression and insomnia, are also abused. Morphine is a very effective sedative and painkiller, useful after surgery, but is abused too.

Tobacco. Used for over 400 years: smoked, chewed or as snuff. It contains the alkaloid nicotine, which stimulates the adrenal gland to release adrenaline and nor-adrenaline, raising blood pressure and heart rate. Smoking is linked to cancers of the lung, urinary bladder and throat, bronchitis, emphysema, coronary heart disease and gastric ulcer; chewing tobacco raises the risk of oral cancer. Smoking raises carbon monoxide in blood and lowers haem-bound oxygen, causing oxygen deficiency. Cigarette packets carry a statutory warning.

Why adolescents start. Adolescence (roughly 12-18 years) is both a period and a process of becoming mature. Common reasons:

curiosity, need for adventure and excitement, experimentation;
using drugs to escape problems; stress to excel in studies and examinations;
the perception that smoking, drugs or alcohol are 'cool' or progressive, promoted by TV, movies, newspapers and the internet;
unstable or unsupportive families and peer pressure.

Addiction and dependence.

Addiction: a psychological attachment to effects such as euphoria and a temporary feeling of well-being, which drives a person to take drugs even when not needed or when use becomes self-destructive.
Tolerance: with repeated use, the tolerance level of receptors increases, so receptors respond only to higher doses, leading to greater intake and addiction.
Dependence: the body shows an unpleasant withdrawal syndrome if the regular dose is stopped abruptly: anxiety, shakiness, nausea and sweating, relieved when use resumes. Withdrawal can be severe, even life-threatening, needing medical supervision. Dependence can make a person ignore social norms to get money for drugs.

Flow chart: curiosity / peer pressure / stress → first use → pleasant effect → repeated use → receptor tolerance → higher doses → addiction (psychological) → dependence (withdrawal on stopping) → health, social and financial damage.

Effects of abuse.

Immediate: reckless behaviour, vandalism, violence; excessive doses can cause coma and death from respiratory failure, heart failure or cerebral haemorrhage; mixing drugs or drugs with alcohol often causes overdose.
Warning signs: drop in academic performance, unexplained absence from school, poor personal hygiene, withdrawal and isolation, depression, fatigue, aggressive and rebellious behaviour, worsening relationships, loss of interest in hobbies, changes in sleeping and eating habits, weight and appetite fluctuations.
Wider effects: stealing for money; intravenous drug users risk AIDS and hepatitis B (shared needles); chronic alcohol use damages the nervous system and liver (cirrhosis); drugs and alcohol in pregnancy harm the fetus.
Misuse in sport: narcotic analgesics, anabolic steroids, diuretics and certain hormones are misused to increase muscle strength and bulk and aggressiveness. Anabolic steroids in females: masculinisation, increased aggressiveness, mood swings, depression, abnormal menstrual cycles, excess facial and body hair, enlargement of the clitoris, deepening of voice. In males: acne, aggressiveness, mood swings, depression, smaller testicles, decreased sperm production, kidney and liver dysfunction, breast enlargement, premature baldness, enlargement of the prostate. In adolescents: severe acne and premature closure of growth centres of long bones (stunted growth).

Prevention and control ('prevention is better than cure'):
1. Avoid undue peer pressure: do not push a child to perform beyond their limits.
2. Education and counselling: teach facing problems and stress, accepting disappointments; channel energy into sports, reading, music, yoga.
3. Seek help from parents and peers, so feelings of anxiety and guilt can be shared.
4. Look for danger signs and take appropriate steps.
5. Seek professional and medical help: psychologists, psychiatrists, and de-addiction and rehabilitation programmes.

Draw and label (diagram asked in some papers): skeletal structure of cannabinoid molecule. Only recognition is needed: a ring structure with a long side chain; label 'cannabinoid molecule'. In written answers, name the source plant and receptor instead of drawing.

Drugs and Alcohol Abuse: key facts

Drug-source pairs: $heroin \leftarrow P a p a v er so mni f er u m; ganja, charas \leftarrow C annabi s s a t i v a; cocaine \leftarrow E r y t h r o x y l u m coc a$; Hallucinogenic plants: Atropa belladonna, Datura.
Mode of action: $opioids: opioid receptors (depressant); cocaine: dopamine transport (stimulant)$; Cannabinoids act on cannabinoid receptors and affect the cardiovascular system.
Nicotine effect: $nicotine \to adrenal medulla \to adrenaline, nor-adrenaline \to B P ↑, heart rate ↑$; Smoking also raises blood CO, lowering haem-bound oxygen.
Addiction cycle: $repeated use \to receptor tolerance ↑\to higher dose \to addiction, dependence$; Withdrawal: anxiety, shakiness, nausea, sweating.
Five preventive measures: $peer pressure ∣ counselling ∣ parents and peers ∣ danger signs ∣ professional help$; De-addiction and rehabilitation programmes.

How to answer Drugs and Alcohol Abuse questions

Most questions name a drug or describe a person's behaviour. Classify, explain the mechanism, then suggest action.

1Identify the drug group and its source plant (opioid-poppy, cannabinoid-Cannabis, coca alkaloid-Erythroxylum).
2State where it acts (opioid receptors, cannabinoid receptors, dopamine transport) and whether it is a depressant or stimulant.
3For a behaviour case, list the warning signs shown, then the likely cause (peer pressure, stress, curiosity).
4For addiction vs dependence, define both and link them through tolerance.
5For sports cases, list effects of anabolic steroids separately for males and females.
6End with specific preventive or corrective measures from the five listed.

Drugs and Alcohol Abuse in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Warning signs and the path to dependence

Suppose a class teacher notices that a usually bright 16-year-old student has started missing classes, scores have dropped sharply, he looks tired, has lost interest in football, and has become irritable with friends. His parents say he now needs money often and sleeps at odd hours.

What might these signs indicate, how could the problem progress if ignored, and what steps should the school and family take?

Try it first, then show the solutionSolution

Drop in academic performance, unexplained absence, fatigue, loss of interest in hobbies, aggressive behaviour, changes in sleep and need for money are warning signs of drug or alcohol abuse.
If ignored: repeated use raises receptor tolerance, so he needs higher doses (addiction); stopping would then cause withdrawal symptoms such as anxiety, shakiness, nausea and sweating (dependence); he could turn to stealing, and injecting drugs could expose him to AIDS and hepatitis B.
Steps: talk with him without blame; avoid undue pressure about marks; counselling on handling stress; involve trusted peers; seek a psychologist or psychiatrist and, if needed, a de-addiction and rehabilitation programme.

Answer: Likely drug or alcohol abuse; it can progress through tolerance to addiction and dependence; respond with support, counselling, reduced pressure and professional help.

Memory hook: Spot the signs early; support beats punishment.

Tricks to remember Drugs and Alcohol Abuse

Short memory aids. Say each one aloud once, then use it on a question the same day.

P-C-E for the three plants
Poppy (opioids), Cannabis (cannabinoids), Erythroxylum (cocaine).
Use it when: Matching drugs to sources.
Heroin hushes, cocaine kicks
Heroin is a depressant (slows the body); cocaine is a stimulant (euphoria, energy).
Use it when: Contrasting effects.
Addiction is in the mind, dependence in the body
Addiction = psychological craving; dependence = physical withdrawal.
Use it when: Defining the two terms.

Drugs and Alcohol Abuse: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Heroin · 2 marks · Very short answerBoard level

Give the chemical name of heroin, its source and its effect on the body.

Try it first, then show the solutionSolution

Diacetylmorphine, obtained by acetylation of morphine extracted from the latex of the poppy, Papaver somniferum (1 mark).
It binds opioid receptors in the CNS and gut; it is a depressant that slows down body functions (1 mark).

Answer: Diacetylmorphine from poppy latex (via morphine); a depressant acting on opioid receptors.

Example 2: Addiction and dependence · 3 marks · Short answerBoard level

Differentiate between addiction and dependence. How does tolerance link the two?

Try it first, then show the solutionSolution

Addiction: psychological attachment to effects such as euphoria and a temporary feeling of well-being, driving use even when self-destructive (1 mark).
Dependence: the body shows withdrawal symptoms (anxiety, shakiness, nausea, sweating) when the regular dose is stopped abruptly (1 mark).
Repeated use raises the tolerance of receptors, so only higher doses work; higher intake deepens addiction and makes the body dependent (1 mark).

Answer: Addiction = psychological craving; dependence = withdrawal on stopping; rising tolerance drives both.

Example 3: Nicotine and smoking · 3 marks · Short answerHarder board level

Explain how smoking raises blood pressure and causes oxygen deficiency in the body. Name two diseases associated with smoking.

Try it first, then show the solutionSolution

Nicotine stimulates the adrenal gland to release adrenaline and nor-adrenaline, which raise blood pressure and heart rate (1 mark).
Smoking increases carbon monoxide in the blood and reduces haem-bound oxygen, causing oxygen deficiency (1 mark).
Diseases: lung, throat or bladder cancer, bronchitis, emphysema, coronary heart disease, gastric ulcer (any two) (1 mark).

Answer: Nicotine → adrenaline/nor-adrenaline → higher BP; CO lowers oxygen carriage; e.g. lung cancer, emphysema.

Example 4: Cocaine · 2 marks · Very short answerHarder board level

Name the source of cocaine and explain how it affects the nervous system. What happens with excessive doses?

Try it first, then show the solutionSolution

Cocaine is a coca alkaloid from Erythroxylum coca, native to South America; it interferes with the transport of the neurotransmitter dopamine (1 mark).
It strongly stimulates the CNS, giving euphoria and increased energy; excessive doses cause hallucinations (1 mark).

Answer: From Erythroxylum coca; blocks dopamine transport; stimulant; hallucinations at high doses.

Example 5: Steroids in sport · 5 marks · Long answerHOTS / competency

Suppose a national-level female athlete and a male athlete both take anabolic steroids for a season. List three effects expected in each and explain why sports bodies ban these substances.

Try it first, then show the solutionSolution

Steroids are misused to increase muscle strength and bulk and aggressiveness (1 mark).
Female: masculinisation, abnormal menstrual cycles, excess facial and body hair, deepening of voice, enlargement of the clitoris, mood swings, depression (any three) (1½ marks).
Male: reduced size of testicles, decreased sperm production, breast enlargement, premature baldness, enlarged prostate, acne, kidney and liver dysfunction (any three) (1½ marks).
They are banned because they give an unfair advantage and cause serious, sometimes permanent, harm to health (1 mark).

Answer: Female: masculinisation, menstrual disturbance, deep voice; male: small testes, low sperm count, breast enlargement; banned for unfairness and health damage.

Example 6: Why adolescents are vulnerable · 3 marks · Short answerHarder board level

Explain any three reasons why adolescents start using drugs or alcohol, and match each with a preventive measure.

Try it first, then show the solutionSolution

Curiosity and experimentation → education and counselling about effects and about handling stress (1 mark).
Peer pressure and the image that drugs are 'cool' (from media) → avoid undue peer pressure; seek help from parents and peers (1 mark).
Stress to excel in studies or escape from problems; unsupportive families → parents should not push beyond limits; professional help from psychologists if needed (1 mark).

Answer: Curiosity, peer pressure, stress/unsupportive family; counselling, family and peer support, reduced pressure, professional help.

Where students lose marks in Drugs and Alcohol Abuse

The slips examiners see most often, and what to write instead.

Mistake: Calling heroin a stimulant
All drugs are thought to 'excite'.
Wrong working
Heroin is a stimulant that increases energy.
Right working
Heroin is a depressant; cocaine is a stimulant.
Do this: Heroin hushes, cocaine kicks.
Usually costs: 1 mark.
Mistake: Wrong source plant
Botanical names are confused.
Wrong working
Cocaine is obtained from Cannabis sativa.
Right working
Cocaine: Erythroxylum coca; cannabinoids: Cannabis sativa.
Do this: Learn the three as a table.
Usually costs: 1 mark.
Mistake: Using addiction and dependence as synonyms
Both mean 'cannot stop' in daily speech.
Wrong working
Dependence is the craving for euphoria.
Right working
Addiction = psychological attachment; dependence = withdrawal symptoms on stopping.
Do this: Mind vs body.
Usually costs: 1 mark.
Mistake: Generic prevention answers
Students write 'say no to drugs'.
Wrong working
Drugs should be avoided.
Right working
Avoid undue peer pressure; education and counselling; help from parents and peers; look for danger signs; professional help and de-addiction programmes.
Do this: Quote the five NCERT measures.
Usually costs: 1-2 marks.

Exam tips

Learn the drug table (group, source, example, route, action); it answers most 2-3 mark questions.
For nicotine, write the full chain: adrenal gland → adrenaline and nor-adrenaline → higher BP and heart rate.
Separate effects of steroids in males and females clearly.
Use the word 'tolerance' when explaining increasing doses.
Keep answers factual and non-judgemental; the paper rewards mechanisms and measures.

Practice questions on Drugs and Alcohol Abuse

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
Which drug is obtained from the latex of Papaver somniferum after chemical modification?
(a) Cocaine (b) Heroin (c) Charas (d) LSD
Hint
Acetylation of morphine.
Answer
(b) Heroin.
Q2 · 1 mark · Assertion-reasonBoard level
Assertion (A): Smokers suffer from oxygen deficiency.
Reason (R): Smoking increases the carbon monoxide content of blood and reduces haem-bound oxygen.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Hint
CO and haemoglobin.
Answer
(a).
Q3 · 2 marks · Very short answerHarder board level
Why are people who inject drugs at higher risk of AIDS and hepatitis B?
Hint
Sharing needles.
Answer
Drug users often share needles and syringes; HIV and hepatitis B virus present in the blood of one user pass directly into the blood of another through the shared needle.
Q4 · 3 marks · Short answerHOTS / competency
Suppose a person who has used alcohol heavily for years decides to stop suddenly and within a day develops anxiety, shaking hands, nausea and sweating. (a) What is this condition called? (b) Why does it happen? (c) What should be done?
Hint
Dependence.
Answer
(a) Withdrawal syndrome, a sign of dependence. (b) With long use, the body and its receptors have adapted to regular doses; abrupt stopping produces characteristic unpleasant withdrawal symptoms. (c) Withdrawal can be severe or even life-threatening, so it should be done under medical supervision, with counselling and a de-addiction and rehabilitation programme.
Q5 · 4 marks · Case-basedHarder board level
Read and answer.
Suppose a student project compares three plant-derived substances: X is taken by snorting and makes the user euphoric and energetic; Y is smoked as ganja and affects the heart and circulation; Z is made from a milky latex and slows body functions.
(a) Identify X, Y and Z. (1)
(b) Name the receptors or transmitter each acts on. (1)
(c) Name the source plants and one other hallucinogenic plant. (2)
Hint
Stimulant, cannabinoid, opioid.
Answer
(a) X = cocaine, Y = a cannabinoid (ganja), Z = an opioid (heroin/morphine). (b) X interferes with dopamine transport; Y acts on cannabinoid receptors in the brain; Z binds opioid receptors in the CNS and gut. (c) X: Erythroxylum coca; Y: Cannabis sativa; Z: Papaver somniferum; other hallucinogenic plants: Atropa belladonna or Datura.
Q6 · 2 marks · Very short answerHarder board level
List five warning signs of drug or alcohol abuse in a teenager.
Hint
School, behaviour, habits.
Answer
Any five: drop in academic performance; unexplained absence from school; lack of interest in personal hygiene; withdrawal and isolation; depression and fatigue; aggressive, rebellious behaviour; strained relations with family and friends; hobbies dropped; altered sleep and eating patterns; fluctuating weight and appetite.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Chemical name of heroin?Show answer
Diacetylmorphine.
2.Which neurotransmitter's transport does cocaine affect?Show answer
Dopamine.
3.Name the alkaloid in tobacco.Show answer
Nicotine.
4.Name two hallucinogenic plants.Show answer
Atropa belladonna and Datura.
5.What is the age range of adolescence?Show answer
About 12-18 years.
6.Name two withdrawal symptoms.Show answer
Anxiety, shakiness, nausea, sweating (any two).

Drugs and Alcohol Abuse: frequently asked questions

What are opioids?

Drugs such as heroin and morphine that bind to opioid receptors in the central nervous system and gut; heroin is a depressant obtained by acetylating morphine from poppy latex.

What are cannabinoids?

Chemicals that act on cannabinoid receptors mainly in the brain; natural ones come from Cannabis sativa and are used as marijuana, hashish, charas and ganja.

What is the difference between addiction and dependence?

Addiction is a psychological attachment to a drug's effects; dependence is the body's withdrawal syndrome when regular use stops.

How does smoking affect health?

Nicotine raises blood pressure and heart rate; smoking increases carbon monoxide in blood and is linked to lung, throat and bladder cancer, bronchitis, emphysema and heart disease.

How can drug abuse be prevented?

By avoiding undue peer pressure, education and counselling, help from parents and peers, watching for danger signs, and professional help through de-addiction and rehabilitation programmes.