Which of the following is considered a Hill criterion for causality in cohort studies?

• A. Randomization
• B. Blinding
• C. Temporality
• D. Placebo control

Answer: (C)

Temporality is the essential idea here: for something to cause an outcome, the exposure must occur before the outcome. In a cohort study you start with people based on whether they were exposed and then follow them over time to see who develops the outcome. That clear time sequence lets you test whether the exposure precedes the disease, which is a prerequisite for establishing causation.

In Hill’s considerations for causality, temporality is necessary—without it you cannot argue that the exposure caused the outcome. The other options describe study design features typical of randomized trials (randomization, blinding, placebo control). While these design elements help reduce bias in experimental settings, they are not Hill criteria for causality in observational cohort studies.