Editing Epidemiology (section)

=== Bradford Hill criteria ===
{{Main|Bradford Hill criteria}}
In 1965, [[Austin Bradford Hill]] proposed a series of considerations to help assess evidence of causation,<ref name="bh65">{{cite journal |last=Hill |first=Austin Bradford |year=1965 |title=The Environment and Disease: Association or Causation? |journal=[[Proceedings of the Royal Society of Medicine]] |volume=58 |pages=295–300 |url=http://www.edwardtufte.com/tufte/hill |pmid=14283879 |pmc=1898525 |issue=5 |doi=10.1177/003591576505800503}}</ref> which have come to be commonly known as the "[[Bradford Hill criteria]]". In contrast to the explicit intentions of their author, Hill's considerations are now sometimes taught as a checklist to be implemented for assessing causality.<ref>{{cite journal |last1=Phillips |first1=Carl V. |author2=Karen J. Goodman |title=The missed lessons of Sir Austin Bradford Hill |journal=Epidemiologic Perspectives & Innovations |volume=1 |issue=3 |date=October 2004 |pmid=15507128 |pmc=524370 |doi=10.1186/1742-5573-1-3 |pages=3 |doi-access=free }}</ref> Hill himself said "None of my nine viewpoints can bring indisputable evidence for or against the cause-and-effect hypothesis and none can be required ''sine qua non''."<ref name="bh65" />

# '''Strength of Association''': A small association does not mean that there is not a causal effect, though the larger the association, the more likely that it is causal.<ref name="bh65" />
# '''Consistency of Data''': Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect.<ref name="bh65" />
# '''Specificity''': Causation is likely if a very specific population at a specific site and disease with no other likely explanation. The more specific an association between a factor and an effect is, the bigger the probability of a causal relationship.<ref name="bh65" />
# '''Temporality''': The effect has to occur after the cause (and if there is an expected delay between the cause and expected effect, then the effect must occur after that delay).<ref name="bh65" />
# '''Biological gradient''': Greater exposure should generally lead to greater incidence of the effect. However, in some cases, the mere presence of the factor can trigger the effect. In other cases, an inverse proportion is observed: greater exposure leads to lower incidence.<ref name="bh65" />
# '''Plausibility''': A plausible mechanism between cause and effect is helpful (but Hill noted that knowledge of the mechanism is limited by current knowledge).<ref name="bh65" />
# '''Coherence''': Coherence between epidemiological and laboratory findings increases the likelihood of an effect. However, Hill noted that "... lack of such [laboratory] evidence cannot nullify the epidemiological effect on associations".<ref name="bh65" />
# '''Experiment''': "Occasionally it is possible to appeal to experimental evidence".<ref name="bh65" />
# '''Analogy''': The effect of similar factors may be considered.<ref name="bh65" />