IB Psychology SLTopic 2 — Health ProblemsPaper 1 & 2Research methods~10 min read
How Common Is Smoking?
Smoking is easier to define than obesity — you either smoke or you do not. The hard part is when. Someone who quit last year, someone who smokes at parties, and someone on twenty a day are all different, and which of them gets counted depends entirely on the type of prevalence being used.
📚 What you need to know
Prevalence can be reported as a percentage or as cases per 10,000 or 100,000 people.
Point prevalence = the proportion smoking at one specific moment.
Period prevalence = the proportion smoking at any time in a set period, such as the past 12 months.
Lifetime prevalence = the proportion who have smoked at any point in their life.
WHO data: in 2022, 20.9% of the world’s population aged 15+ smoked cigarettes.
Around 80% of the world’s 1.25 billion tobacco users live in low- and middle-income countries.
Valente et al. (2005) is your study, and its finding about popularity is counter-intuitive.
Three ways to count the same people
This distinction is worth two minutes of your revision time and it earns marks whenever a question mentions prevalence.
🧩 Which figure would be biggest?
Lifetime prevalence is always the largest, because once you are in, you never leave the count.
Period prevalence sits in the middle — it catches occasional smokers and people who quit partway through the year.
Point prevalence is the smallest, because it only counts people smoking right now.
So a headline saying “smoking rates have halved” means very little until you know which of the three is being reported. Two countries can look completely different simply because they chose different definitions.
Global trends
Global prevalence of smoking is declining each year.
But some countries, including Egypt, Jordan and Indonesia, show rising rates among men.
In 2022, 34.4% of men and 7.4% of women used tobacco. In 2000, around 16.3% of women did.
Dashed sections are projections, not measurements. Treat them as an assumption about the future that could be wrong, and say so if you use them in an answer.
Why the ratio widens even though both fall
The male-to-female ratio has stretched steadily: men were about 3 times more likely to smoke in 2000, 4 times in 2022, and are projected to be 5 times more likely by 2030.
That happens because women started from a much lower base. Falling from 16.3% to 7.4% is a bigger relative drop than falling from 49% to 34%, even though the second one is a bigger drop in percentage points. Two true statements that sound contradictory — being able to explain both is exactly the kind of thing that separates a 6 from a 7.
Regional detail is worth learning because it stops your answer sounding generic. Female prevalence in South-East Asia was the world’s highest in 2000 at around 33%, and had fallen to about 10% by 2022. Europe now has the highest female prevalence at roughly 18%, and its decline is slower than Asia’s. So “women smoke less” hides a complete reversal in which region leads.
Age
15 to 23 years: approximately 13% use tobacco.
45 to 54 years: the highest prevalence overall, at 18 to 28%.
85+ years: approximately 13%.
After around 54, prevalence declines as smokers age — partly because people quit, and partly because of the health impacts and mortality among long-term users. That second reason is uncomfortable but it is a real part of the explanation, and a strong answer says it.
🔬 Valente et al. (2005)
Do popular students start smoking?
AIM
To investigate whether popular students are more likely to start smoking.
PARTICIPANTS
1,486 students aged 12 to 14 (grades 6 and 7) from 16 middle schools in southern California.
PROCEDURE
Three surveys were used: a baseline survey measuring gender, ethnicity, age, grades, susceptibility to smoking and smoking behaviour; a survey two months later measuring social networks; and a one-year follow-up. Susceptibility was measured as a refusal to commit to never smoking in future. Smoking was defined as having ever puffed or smoked a cigarette. Popularity was defined as the number of times a student was chosen as a friend by others.
RESULTS
Popular students were 5 times more likely to smoke than average students. Unpopular or isolated students were also more likely to be susceptible, or to have already started.
CONCLUSION
Popular students influence social norms: when they smoke, peers see it as acceptable or desirable. Because they are more socially connected, their influence spreads more widely.
Notice the shape of that result. Both the most popular and the most isolated students were at higher risk. That is a U-shaped pattern, not a straight line — and it means “peer pressure” is too simple an explanation. The popular students are setting the norm; the isolated ones may be reaching for something else entirely.
Evaluating smoking prevalence research
Strengths
Understanding prevalence is vital given the serious health risks of nicotine addiction.
Valente’s study highlights the importance of early intervention in adolescence.
A large sample across 16 schools improves generalisability within that population.
The one-year follow-up shows change over time rather than a snapshot.
Limitations
Knowing prevalence is not enough — governments still face real difficulty implementing effective interventions.
Prevalence data is descriptive, not explanatory: it does not reveal why people smoke.
Defining smoking as “ever puffed a cigarette” is very broad and may overstate the figures.
More qualitative research is needed to explore cultural, social and psychological causes.
Linking to the concepts
Change: smoking decreases with age, which may reflect health problems developing, such as breathing difficulties, lung and heart disease. Quitting may also follow starting a family and not wanting to expose children to smoke. Smoking bans and increased awareness have contributed to falling rates.
Causality: prevalence rates can only show what is happening, never why. Researchers can infer reasons behind a decline, but there is no real way to establish cause and effect between, say, a health campaign and people quitting. Only a relationship can be pointed to.
EXAM ANSWER
Explain prevalence rates of one health problem. [9 marks]
Define, and split it three ways
Prevalence is how common a behaviour is in a population over a period. It can be point, period or lifetime, and the type chosen changes the number.
Give the global picture
WHO: 20.9% of people aged 15+ smoked in 2022; around 80% of 1.25 billion users live in low- and middle-income countries.
Add a pattern, not just a number
Men 34.4% vs women 7.4%, with the ratio widening from 3:1 to a projected 5:1 by 2030.
One limitation
Prevalence is descriptive only, and definitions such as “ever puffed a cigarette” affect what gets counted.
Link: useful for targeting policy, useless for explaining behavioura definition point is worth as much as a statistic here
💡 Exam tips
Name all three types of prevalence and say which would be largest. Fast marks.
Pair a global figure with a regional one. It shows you understand variation, not just headlines.
Always flag projections as projections. Treating 2030 as a fact is a mistake examiners notice.
The U-shaped popularity finding is memorable and rare — use it.
The operational definition of “smoking” is a strong methodological criticism. Point it out.
Valente also works for social learning theory and for research methods on self-report surveys.
⚠ Common mix-ups
Saying smoking is rising globally. It is falling globally, but rising among men in some countries.
Reading “5 times more likely” as 5 times the total. It is 5 times the rate of average students.
Assuming a falling percentage means fewer smokers. Population growth means the absolute number can still rise.
Confusing period and lifetime prevalence. Lifetime never resets.
Only mentioning popular students. Isolated students were also at higher risk.
Treating the sample as global. Valente studied 12 to 14 year olds in southern California.
Up next: Why Obesity Rates Differ Between Cultures — we have counted. Now we start explaining, and Hofstede’s dimensions come back for a second job.
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