Prevalence of health problems
IB Psychology· Health and well-being· 14 min read
1. Core concept
Prevalence is how common a health problem is in a population. It changes over time and differs between populations — obesity, for example, has risen steeply in many countries over recent decades, while estimates of newer problems like 'social media addiction' vary enormously. Two kinds of factor drive the numbers: real changes (environment, diet, technology, age structure) and measurement changes (what criteria and questionnaires define a 'case', and how the sample was drawn). A rising or differing prevalence figure therefore has to be read carefully — part real trend, part artefact of definition.
2. Key studies
IB Psychology answers must be supported by named studies. Learn these to cite as evidence:
Schramm et al. (2023)
Obesity prevalence in Denmark rose from 6.1% to 18.4% between 1987 and 2021, with strong period effects (rising across all age groups) but no cohort effects. — Anchors a real change in a health problem's prevalence over time and distinguishes period from cohort explanations.
Cheng et al. (2021)
A meta-analysis estimated social-media-addiction prevalence at ~25%, but with wide variation driven by diagnostic criteria, questionnaire quality, culture and sampling. — Anchors a second health problem and shows how much a prevalence figure depends on measurement, not just reality.
3. Evaluation (AO3)
Strength — reveals genuine trends — Population data over time (Schramm) and pooled across studies (Cheng) can expose real trends in a health problem and the factors behind them.
Limitation — only as good as the case definition — Differing criteria, self-report questionnaires and sampling make figures hard to compare, so apparent differences or increases can be measurement artefacts.
4. Scope
5. Common Pitfalls
Wrong move:
Reading a rising or higher prevalence figure as purely a real increase in the problem.
Why:
A frequently penalised misconception in IB Psychology exams.
Correct move:
Prevalence depends on how a 'case' is defined and measured — changed criteria, greater awareness, and different questionnaires or samples can inflate or deflate the number independent of any real change.
Going deeper
- Culture and prevalence of disorderscultural/population differences in DISORDER prevalence are the parallel card (HWB_3).
- Prevention/treatment of a health problemprevention strategies respond to prevalence (HWB_9).
- Social learning and healthsocial learning is one factor behind a changing prevalence (HWB_6).