Bradford Hill’s Criteria for Inferring Causality

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

3. Why? • Lots of easy marks for not much revision • 3, 4, 6 marks? • 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

5. 9 Criteria

6. Mnemonic

7. Mnemonic

8. Haribo + Diabetesin Peer Support Students

9. A causal link is more likely with strongassociations(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. 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. 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