Causation

Question 1

Who cares about causation? (5)

Answer 1

• Patients
• Carers and relatives
• Health professionals
• Researchers
• Readers of medical journals

Question 2

Why is cause important? (3)

Answer 2

• To know why things happen
• To prevent disease by removing the cause
• To improve treatment through greater understanding of natural history of disease

Question 3

How can we prove causation? (3)

Answer 3

• Find an association
• Consider what might cause the association
• Use criteria that help inform a decision

Question 4

Who argued falsifiability?

Answer 4

Karl Popper (1934)

Question 5

What is falsifiability?

Answer 5

Can’t prove a theory is true, but can prove a theory is false

Question 6

What factors would you consider when finding an association? (4)

Answer 6

• Is it any more common than you would expect?
• Degree of association
• Statistical significance
• Clinical significance

Question 7

What is chance?

Answer 7

• Random error - associations purely happen by chance
• e.g. lottery winners

Question 8

What is bias?

Answer 8

• Systematic error in the collection or analysis of information
• E.g. coffee drinkers are more likely to approve of the brand they already drink

Question 9

What does WEIRD stand for and what is its significance?

Answer 9

Represents up to 80% of study participants, but only 12% of the world’s population
- Western
- Educated
- Industrialised
- Rich
- Democratic

Question 10

What are cofounding variables?

Answer 10

Both factors are not directly associated but are linked by a third factor

Question 11

What are the components of the Bradford Hill Criteria? (9)

Answer 11

1. Strength of association
2. Temporal association
3. Consistency
4. Theoretical plausibility
5. Coherence
6. Specificity
7. Dose response relationship
8. Experimental evidence
9. Analogy

Question 12

What is strength of association?

Answer 12

How strong is the association

Question 13

What is temporal association?

Answer 13

The effect must occur after the cause

Question 14

What is consistency?

Answer 14

Consistent findings observed strengthen the likelihood of an effect

Question 15

What is theoretical plausibility?

Answer 15

• Understanding of the mechanisms helps ascertain causality
• E.g. does high fat diet cause coronary heart disease?

Question 16

What is coherence?

Answer 16

• Coherence between epidemiological and laboratory findings increases the likelihood of an effect
• E.g. does bacteria cause sexually transmitted infections?

Question 17

What is specificity?

Answer 17

• Causation is likely if there is a specific population at a specific site with no other likely explanation
• E.g. does vinyl chloride monomer cause hemangiosarcoma?

Question 18

What is the dose response relationship?

Answer 18

• Greater exposure should generally lead to greater effect
• E.g. does exercise improve health?

Question 19

What is experimental evidence?

Answer 19

Evidence from laboratory experiments

Question 20

What is analogy?

Answer 20

• The use of analogies or similarities between the observed association and any other associations
• E.g. does passive smoking cause cancer

Question 21

What is research design?

Answer 21

How would we design research to test cause and effect

Question 22

Cross-sectional studies can help generate what…?

Answer 22

Generate hypotheses but not prove causality

Question 23

How can experimental evidence increase confidence in finding causation? (2)

Answer 23

• Randomisation
• Importance of time (before and after)

Question 24

What are some difficulties with causation and association? (3)

Answer 24

• A cause may be sufficient or not
• A cause may be necessary or not
• One cause may be preceded by another and by another
• E.g. what causes people to smoke in the first place?

Question 25

What does ecological fallacy refer to?

Answer 25

Individuals and populations differ