Hills Criteria of Causality

strength

the larger an association between exposure and disease, the more likely it is to be causal.

consistency

Multiple epidemiologic studies using a variety of locations, populations, and methods show a consistent association

specificity

associations are more likely to be causal when they are specific, meaning the exposure causes only one disease

Temporality

exposure must precede the onset of disease.

Biological gradient

if a dose response is seen, it is more likely that the association is causal

plausibility

the relationship is consistent with the current body of knowledge regarding the etiology and mechanism of disease

coherence

the cause-and-effect story should make sense with all knowledge available to the researcher.

experiment

evidence drawn from experimental manipulation may lead to the strongest support for causal inference.

analogy

when one causal agent is known, the standards of evidence are lowered for a second causal agent that is similar in some way.