Concept of Health and Disease
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Direct answer
Health, per the WHO Constitution of 1948, is "a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity" — a definition criticised as utopian because it ignores degrees of wellness and the reality of living well with disability, yet it remains the anchor of every PSM viva. Disease is a physiological or psychological dysfunction, while illness is what the patient feels and sickness is the social role society assigns. Between health and disease lie recognised intermediate states — subhealth or predisease — which is why community medicine studies populations on a spectrum rather than as a healthy/diseased binary.
What you must remember
- WHO definition (1948): complete physical, mental and social wellbeing, not merely absence of disease or infirmity; the 1986 Ottawa Charter adds "resource for everyday life", a social dimension.
- Dimensions of health: physical, mental, social, spiritual and emotional — the four/five-dimension model; spiritual health includes integrity, service and a sense of purpose.
- Changing concepts: biomedical (absence of disease) → ecological (balance of agent, host and environment) → psychosocial (add behaviour and psychology) → holistic (all dimensions plus harmonious functioning).
- Disease terminology: disease = objective pathological process; illness = subjective patient experience; sickness = societal role; sickness could be feigned or socially imposed.
- Epidemiological triad: agent, host and environment interact in prepathogenesis; removing any arm breaks the causal chain — the logic behind chlorination, immunisation and quarantine.
- Multifactorial causation: the web of causation (MacMahon and Pugh) replaced single-cause germ theory; coronary heart disease needs dozens of contributing causes, none alone sufficient.
- Concept of wellbeing: objective component (standard of living — income, housing, nutrition) and subjective component (quality of life, life satisfaction, happiness), assessed by tools such as the WHO-5 and health-adjusted life expectancy.
- Health as a right: the Indian Constitution does not list health as a fundamental right but folds it into Article 47 (Directive Principle — raising of the level of nutrition and standard of living), a favourite one-liner in university theory papers.
How concepts evolved into practice
Trace one disease through these ideas and the whole chapter snaps into focus. Cholera in nineteenth-century London looked like a single-cause problem — Vibrio cholerae, a classic agent — yet John Snow controlled it by removing an environmental arm (the Broad Street pump handle) decades before the organism was identified. That is the ecological concept in action: agent, host and environment in dynamic balance, with intervention possible at any arm. Modern noncommunicable disease epidemiology pushes the same logic further through the web of causation: a myocardial infarction in a 50-year-old Indian truck driver is woven from tobacco, salt, sedentary work, abdominal obesity, diabetes and stress, and the web implies there is no single thread to cut — hence multiple simultaneous interventions such as tobacco taxation, screening camps at the workplace and lipid-lowering drugs.
The health-illness continuum completes the picture. A newly diagnosed hypertensive executive is neither fully healthy nor classically diseased; he sits on a spectrum that community medicine tries to shift leftward through primordial prevention. This continuum is exactly what screening programmes operationalise, picking people out of the "healthy" pool before symptoms declare themselves.
How the exam frames it
University papers love two essay hooks here: "Define health and discuss its dimensions" and "Describe the changing concepts of health and disease." The trap is writing the WHO definition and stopping — examiners want the criticism (complete wellbeing is unattainable and unmeasurable) and the evolution of concepts in sequence. In vivas, the trio of disease, illness and sickness gets asked as a rapid-fire: expect "A diabetic who feels perfectly well has disease but no illness," and "A malingerer claims sickness without disease." Another favourite contrast: standard of living (material, income-based, objective) versus quality of life (perceived, subjective, WHOQOL-measured) — candidates who reverse these two lose easy marks.
Frequently asked questions
What is the WHO definition of health and when was it framed?
Health is a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity, framed in the WHO Constitution of 1948.
How does disease differ from illness and sickness?
Disease is the objective, measurable pathological dysfunction; illness is the individual's subjective experience of feeling unwell; sickness is the socially recognised role assigned to the sick person.
What are the four changing concepts of health?
Biomedical, ecological, psychosocial and holistic — each adds a layer of determinants beyond the laboratory, culminating in whole-person and whole-population thinking.
What is the web of causation?
Proposed for chronic multifactorial diseases, it depicts disease as arising from a tangled web of interacting agent, host and environmental factors rather than one necessary and sufficient cause.
Where does health appear in the Indian Constitution?
Health is not a fundamental right; Article 47, a Directive Principle of State Policy, obliges the State to raise the level of nutrition and the standard of living and to improve public health.