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IB DP Psychology — Health and Well-Being (Contexts) | SL & HL | Paper 2
🎯 Learning Intentions By the end of this note, you will be able to:
- Define prevalence, incidence, and health problem using IB-aligned terminology.
- Explain how biological, cognitive, and sociocultural factors contribute to the prevalence of health problems.
- Describe the role of socioeconomic status, culture, and lifestyle in shaping patterns of health and illness.
- Evaluate research evidence on the prevalence of health problems using supporting and opposing studies in ACAS format.
- Apply concepts of health prevalence to a real-world case study from multiple psychological perspectives.
- Discuss the extent to which social determinants of health explain differential rates of illness across populations.
- Analyse research on health prevalence using relevant concept areas: Bias, Causality, Perspective, and Responsibility.
Introduction & Context
Consider two people living in the same city. One grows up in a well-resourced neighbourhood, attends good schools, eats nutritious food, and has access to healthcare whenever needed. The other grows up in poverty, experiences chronic stress, lives in a polluted environment, and rarely sees a doctor. By middle age, their health trajectories look dramatically different — one is thriving, the other is managing multiple chronic conditions. What explains this gap? Is it simply bad luck, or are there systematic forces at work?
This is the central question behind the study of health prevalence in psychology. Rather than asking "what causes a specific disease?", psychologists ask "why do certain health problems appear more frequently in some groups, communities, or societies than others?" The answer, as decades of research demonstrate, is rarely simple. Biological vulnerabilities interact with psychological states and social conditions to produce patterns of illness that are anything but random. Understanding these patterns — who gets sick, how often, and why — is the foundation of health psychology.
🔍 Analogy — The Leaking Roof Imagine a building where some rooms always seem to get wet when it rains, while others stay dry. You could spend all your time mopping up the water in the wet rooms (treating illness), or you could climb up and find out why certain parts of the roof are structurally weaker (addressing the conditions that make some people more vulnerable to health problems). Studying prevalence is like examining the roof — it tells us where the vulnerabilities are and why they exist, so we can address causes rather than just symptoms.
Core Concepts
Before we can analyse why health problems are distributed unevenly across populations, we need precise language to describe what we are measuring. When researchers talk about how common a health problem is, they are drawing on two related but distinct concepts that are easy to confuse but carry very different meanings for public health and psychology.
📖 Key Definition — Prevalence Prevalence refers to the total proportion of individuals in a defined population who have a particular health condition at a specific point in time (point prevalence) or over a defined period (period prevalence). It is typically expressed as a percentage or as cases per 1,000 or 100,000 people.
Prevalence is essentially a snapshot — it tells us how widespread a condition is right now, or across a given window of time. For example, the World Health Organization estimates that approximately 5% of adults globally live with depression at any given time. This