The 'Bradford Hill criteria' are used to establish causal inference in observational epidemiology. Which criterion states that the exposure must precede the disease outcome?
- A Consistency
- B Plausibility
- C Temporality ✓
- D Coherence
Correct answer: C. Temporality
Explanation
Temporality — the exposure must precede the outcome — is the only criterion considered absolutely necessary for causality among Bradford Hill's nine criteria (1965). The others (strength, consistency, specificity, dose-response/biological gradient, plausibility, coherence, experiment, analogy) support but do not alone establish causation. Cross-sectional studies cannot easily establish temporality, which is a key methodological limitation for causal inference.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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