Healthy Lifestyle - THEORIES OF DISEASE CAUSATION

Germ theory of disease (monocausal)

Work of Koch and Pasteur revealed that the prevailing health problems of the time were the products of living organisms. Isolation of bacillus causing tuberculosis and identification of the organism responsible for 22 infectious diseases between 1880 to 1900, gave rise to the idea that each disease had a single and a specific cause. A set of rules was formulated by Koch (Koch postulates) for establishing causal

relationship between a microorganism and a disease states. In brief, it was essential that to be ascribed a causal role, the agent must always be found with the disease in question and not with any other disease.

Epidemiological triad

The germ theory could not explain

why not all those exposed to pathogen become ill: an

organism or other noxious agent is a necessary, but not a

sufficient cause of disease. The epidemiological triangle

approach sees disease as the product of an interaction

between an agent, a host, and the environment. The epidemiological triangle is useful in understanding infectious

disorders, but is less useful with respect to chronic and

degenerative disorders such as stroke arthritis and heart disease

Web of causation

The web of causation considers all the predisposing factors of any type and their complex interrelationship with each other. This model is ideally suited for study of chronic diseases, where the disease agent is often not known. The disease is the outcome of the interaction of the multiple factors. It does not mean that to control a disease all or most of the factors need to be removed or controlled. The removal or elimination of even one factor may sometime be sufficient to control a disease provided that factor is sufficiently important.

The theory of general susceptibility

This theory has emerged over the past 25 years and is different in important ways from monocausal and multicausal cause of disease. It is not concerned with identifying single or multiple risk factors associated with specific disorders. It seeks to understand why some social groups are more susceptible to disease and death in general.

The socio-environmental approach

During the 1980s, the theory of general susceptibility became more explicitly formulated as the socio-environmental approach. This approach seeks to identify the factors which make and keep people healthy and is not much concerned with the cause of the disease. It focuses on the population rather than the individuals. It forms the basis for the health promotion strategies