1. Bradford Hill’s Criteria for Inferring Causality
Alex Ashley for Peer Support

3. Why? Lots of easy marks for not much revision It’s easy to mark
Make or break that question
It’s easy to mark
Don’t have to be a medic to mark it
It’s easy to discriminate between the good students and the poor ones
You know it or you don’t
Spot when they’re asking for it (and when they’re not)
Get the words right

4. Three Groups of Criteria
Association Features
Other Evidence
Exposure / Outcome

5. 9 Criteria Association Features Other Evidence Exposure / Outcome
Strength of Association
Specificity of Association
Consistency of Association
Other Evidence
Coherence of Theory
Biological Plausibility
Analogy
Exposure / Outcome
Temporal Sequence
Dose Response
Reversibility (Experiment)

6. S C B A T D R Mnemonic Association Features Other Evidence
Exposure / Outcome T D R

7. Mnemonic Some Stupid Children Can’t Be Arsed To Do Revision
Association Features
Some
Stupid
Children
Other Evidence
Can’t Be
Arsed
Exposure / Outcome To Do
Revision

8. Haribo + Diabetes in Peer Support Students

9. Association Features Strength of Association
Specificity of Association
Consistency of Association
A causal link is more likely with strong associations (RR or OR)
Peer support students who eat Haribo are twice as likely to get diabetes
A causal link is more likely when a disease is associated with one specific factor and vice versa
The only way to get diabetes is to eat Haribo
A causal link is more likely if the association is observed in different studies and different sub-groups
Female peer support students who eat Haribo get diabetes too

10. Biological Plausibility
Other Evidence
Coherence of Theory
Biological Plausibility
Analogy
A causal link is more likely if the observed association conforms with current knowledge
We know high sugar diets can lead to insulin insensitivity
A causal link is more likely if a biologically plausible mechanism is likely or demonstrated
Cells fail to respond adequately to normal levels of insulin
A causal link is more likely if an analogy exists with other diseases, species or settings
Psychology students who eat Haribo have more cavities

11. Exposure / Outcome Temporal Sequence Dose Response Reversibility
(Experiment)
A causal link is more likely if exposure to the putative cause has been shown to precede the outcome (RCTs, cohort)
Students didn’t have diabetes before they came to Peer Support
A causal link is more likely if different levels of exposure to the putative factor lead to different risk of acquiring the outcome
Students who eat the whole bag of Haribo get diabetes more often than those who pick out one or two
A causal link is very likely if removal or prevention of the putative factor leads to a reduced or non-existent risk of acquiring the outcome
Students sitting at the tables with fruit instead of Haribo don’t get diabetes