Most of our public debates these days are about cause and effect: do vaccinations cause autism? Do carbon emissions cause climate change? Do mobile phones cause tumours? Typically, these sort of discussions get pretty heated because knowing what is (and is not) to blame is a tricky business; it’s easy to get confused when talking about causality.
Which is why a brilliant epidemiologist, Dr Austen Bradford Hill (1897-1991) identified nine logical hurdles for eliminating causal connections that shouldn’t have been made in the first place.
So, for example, I’ve always suspected that red wine makes me stupid. Let’s put my theory on the track and see how many of Hill’s hurdles it can clear.
#1. The effect (stupidity) is way above normal levels. (That’s a big YES.)
#2. It happens every single time without fail. (Yep, without fail.)
#3. The cause (red wine) always and only ever produces the effect. (Oh yeah.)
#4. The sequence never changes. (Right again.)
#5. A bit causes a little effect , a lot causes a big effect. (Yep.)
#6. The suspected relationship obeys the laws of nature and of logic. (Yes it does.)
#7. It makes sense with everything else we know. (Tick.)
#8. Anyone else would get the same effect if they tried it. (I’ve asked… and they do.)
#9. Other things like this (say, whisky) work like this too. (True.)
So it looks like my theory is through to the semi-finals (along with the carbon-climate theory which clears each hurdle without breaking a sweat). But it’s a disappointing race for the vaccination-autism theory, which stumbles at the first hurdle, crashes at the second and bursts into flame at the third. (The mobile-tumour theory has yet to make it onto the track, as we’re still not sure there’s an effect, let alone a cause).
Hill’s test is a quick way to sort sense from nonsense and has been standard medical practice since the 1960’s. It’s just a shame it hasn’t yet found its way into our public ‘debate’, which seems to be pushing our general level of stupidity to way above normal.
It’s enough to drive a man to drink.