How to Prove x caused y, or Causation

Hill's Criteria for Causation

Nine criteria must be met to establish a cause-and-effect relationship. This is commonly known as Hill's Criteria for Causation.

  1. Strength of association - relationship is clear and risk estimate is high *
  2. Consistency - observation of association must be repeatable in different populations at different times *
  3. Specificity - a single cause produces a specific effect
  4. Alternative explanations - consideration of multiople hypotheses before making conclusions about whether an association is causal or not
  5. Temporality - cause / exposure must precede effect / outcome *
  6. Dose/response (biologic gradient) - increasing risk is associated with increasing exposure *
  7. Biological plausibility - the association agrees with currently accepted understanding of biological and pathological processes; the biological explanation makes sense; *
  8. Experimental evidence - the condition can be altered, either prevented or accelerated, by an appropriate experimental process
  9. Coherence - the association should be compatible with existing theory and knowledge, including knowledge of past cases and epidemiological studies; 1-1 relationship - exposure is always associated with outcome / outcome is always caused by a specific exposure *

* These items are identified as criteria to draw conclusions <Why are some excluded?>

Additional information:

History of Hill's Development of these criteria