# Concept of Health and Disease > Concept of health and disease for MBBS Community Medicine: WHO definition, dimensions, changing concepts and the epidemiological triad explained. - Canonical URL: https://prepelephant.com/topics/mbbs/community-medicine/concept-of-health-and-disease - Exam / course: MBBS · Subject: Community Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Concept of Health and Disease", PrepElephant, https://prepelephant.com/topics/mbbs/community-medicine/concept-of-health-and-disease ## 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.