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Bradford Hill criteria

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[A. B. Hill (1897–1991), British medical statistician] A set of nine criteria used to determine the strength of an association between a disease and its supposed causative agent. They form the basis of modern medical and dental epidemiological research.

The nine Bradford Hill criteria



Strength of association

The stronger the association, the more likely it is that the relation is causal.

Temporal relationship

Exposure always precedes the outcome.


The association is consistent when results are replicated with different people under different circumstances and with different measurement instruments.

Theoretical plausibility

It is easier to accept an association as causal when there is a rational and theoretical basis for such a conclusion.


The association should be compatible with existing theory, hypotheses, and knowledge.


In the ideal situation, the effect has only one cause.

Dose response relationship

An increasing amount of exposure increases the risk.

Experimental evidence

Any related research that is based on experiments will make a causal inference more plausible.


Sometimes a commonly accepted phenomenon in one area can be applied to another area.

Reference entries