Hill described criteria for determining if an exposure was causal for an outcome. These criteria work fine for many toxic, traumatic and infectious disorders, but they may be elusive for weaker exposures that may take years to result in an outcome.



(1) temporal sequence

(2) strength of association

(3) consistency of the association

(4) specificity of the association

(5) dose response relation (biological gradient)

(6) biological plausability

(7) coherence with existing knowledge

(8) analogy

(9) experimental evidence


These criteria differ in their relative strength:

(1) strong evidence: experimental evidence; temporal sequence

(2) intermediate: dose-response gradient (for dose-dependent effect); strength of association; consistency of the association

(3) relatively weak: specificity of the association; biological plausability; coherent with existing knowledge; analogy


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