Basic criteria to establish causality
The basic criteria to establish causality are commonly known as the Bradford Hill criteria. These criteria were proposed by Sir Austin Bradford Hill in 1965 to help establish a causal relationship between a particular exposure and a disease or outcome.
Temporality: The cause must come before the effect in time, meaning the exposure must occur before the outcome.
Strength of association: There should be a strong association between the exposure and the outcome. The larger the effect size, the more likely it is that the association is causal.
Biological gradient: There should be a dose-response relationship between the exposure and the outcome. In other words, the greater the exposure, the greater the effect.
Consistency: The association should be consistent across different populations, settings, and study designs.
Specificity: The exposure should be specific to the outcome. In other words, the exposure should only be associated with one outcome, and vice versa.
Coherence: The association should be coherent with known biological mechanisms and knowledge.
Biological plausibility: The association should be biologically plausible and supported by current scientific knowledge.
Analogy: The association should be similar to other known associations between exposures and outcomes.
Experimental evidence: Evidence from experimental designs, such as randomized controlled trials, can help support the causal relationship between exposure and outcome.
It's important to note that not all criteria need to be met for a causal relationship to be established, and the strength of the evidence needed to establish causality can vary depending on the research question and context. However, these criteria serve as a useful framework for evaluating the strength of evidence supporting a causal relationship.
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