Table 1.

Bradford Hill criteria numerical designations and descriptions

BHC	BHC #	Description
Temporal relationship	1	Does the exposure precede the outcome?
Strength of relationship	2	Level of evidence, ROB, study quality
Dose-response relationship	3	U-shaped, inverse U-shaped, etc.
Replication of findings	4	Across studies, across research groups, etc.
Biological plausibility	5	Do the findings make biological sense?
Cessation of exposure	6	Do the effects change after discontinuation?
Specificity of association	7	Does the exposure lead to the outcome?
Coherence between multiple approaches	8	How well do different lines of experimentation or observation support one another?

BHC, Bradford Hill criteria; ROB, risk of bias.