Criteria for Causality: Bradford Hill Criteria - I

Sir Austin Bradford Hill suggested nine criteria for causality, out of which strength, consistency, specificity, and temporality are explained here.

The strength or effect size criterion implies that the stronger the association, the more likely it is to imply causality.

For example, the association between smoking and lung cancer is robust, with smokers having a significantly higher risk of lung cancer compared to non-smokers.

The consistency criterion suggests that consistent observation of the association by various investigators in different settings and under other circumstances increases the likelihood of causation.

One instance of this criterion is the link between smoking and lung cancer, observed in numerous studies across various populations and periods.

The specificity criterion is about a cause leading to a specific effect. This criterion is fulfilled when a particular causative agent is associated with a specific disease, such as the Bacillus anthracis bacterium causing anthrax.

The temporality criterion suggests that the cause must precede the effect.

For instance, asbestos exposure must occur before the development of mesothelioma, a type of cancer affecting the lungs.