Table 4
The strength of the associationThe greater the magnitude of the association the greater the likelihood that it is causal
ConsistencyIf the association is observed at different times, places and by different researchers it is more credible
SpecificityThe more specific the disease and the groups of people affected the greater the likelihood of causality
Temporal relationDoes the suspected cause precede the disease
Biological gradientIs there a doseā€“response type relation
Biological plausibilityDo the findings fit with plausible biological and disease mechanisms
Coherence of the evidenceThe cause and effect interpretation should fit with other known facts regarding the natural history and biology of the disease
PreventionDoes avoidance or removal of the cause decrease the incidence of the disease
Reasoning by analogyDoes the evidence mirror or match another cause and effect relation