Why is the world overflowing with quack treatments? The list is endless, and runs the full gamut from folk remedies for colds to exorcisms for mental illness. What they all have in common is that they are stubbornly popular, despite the fact that they don't work or are even harmful.
Well here's a thought: perhaps they are popular because they don't work. Sound ridiculous? Then read on…
New out in PloS ONE is a model of the uptake of medical treatments, both effective and ineffective, by a multidisciplinary team (evolutionary biologists Mark Tanaka (University of New South Wales) and Kevin Laland (University of St Andrews), and anthropologist Jeremy Kendal).
They started from two basic assumptions: that people start using new treatments (both effective and ineffective) when they see other people using them, and that they stop using treatments if their disease drags on. Crucially, the model creators assume that people have no direct way of telling whether a treatment is effective or not.
What happens next depends on the other assumptions. The simplest case is for illnesses from which people recover naturally and don't relapse. In this scenario, ineffective, magic-based medicine is in fact highly likely to spread.
Why? Simply because the disease lasts longer if the treatment doesn't work, and that means more opportunities for others to learn about it and pick it up themselves.
Now, there is a countervailing effect, of course. Diseases that drag on are likely to trigger people to abandon their treatment. Which effect wins (picking up ineffective treatments, or abandoning treatments as the disease drags on) depends on the assumptions you feed into the model.
Illnesses with a quick spontaneous recovery and people who are reluctant to abandon treatments are fertile territory for magical cures. One implication is that people and societies that are highly conservative (meaning that they are resistant to change) will find themselves lumbered with useless medicines.
If you complicate the model, then the prospects for effective treatments get better. For example, if people can learn about treatments from those who have recovered, then the advantage that magical medicine gets from prolonging disease drops.
And if the disease can recur, then the chances of transmitting effective, rather than ineffective treatments goes up again.
So this model makes some pretty concrete predictions. Magic-based medicine will be particularly popular to treat diseases that clear up by themselves, that rarely re-occur, and where people look for advice mainly to people who have the disease now, rather than at some time in the past. And it will also be prevalent in societies where tradition has a powerful hold.
Is this prediction valid? Well, my totally subjective opinion is that, in Western society at least, most purveyors of quack medicine target people with chronic, non-life threatening conditions. A quick shufty at WorldHealthCenter reveals that the top 5 products all target chronic digestive problems or fear of heavy metal poisoning.
Not really what this model predicts. But this probably reflects the prevalence of these health concerns and the prophylactic nature of the treatment, rather than a predilection for magical cures.
What's more, there is another powerful factor at work here – prestige bias (i.e. we tend to defer to the opinion of doctors, especially for serious conditions). So proper testing of the model will take some real investigative work.
There's a nagging question though. What about that assumption made right up front – that people adopt treatments regardless of their effectiveness? Common sense says that's not going to happen – people are obviously going to prefer the treatments that appear to be effective.
Except it's not that simple to work out which treatments work, and which don't. Modern medicine relies on large, carefully controlled trials to sort the wheat from the chaff – and even then it can take trials recruiting hundreds or even thousands of patients to detect the signal through the statistical noise.
Your average person – no matter how smart or how diligent – hasn't got a hope. In some ways, it's a miracle that any traditional remedies are effective at all!
Tanaka, M., Kendal, J., & Laland, K. (2009). From Traditional Medicine to Witchcraft: Why Medical Treatments Are Not Always Efficacious PLoS ONE, 4 (4) DOI: 10.1371/journal.pone.0005192
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