| Dud treatments more easily spread|
|Ineffective treatments are more likely to spread than effective ones because they are used for a longer period of time, say Australian and UK researchers.|
Dr Mark Tanaka of the University of New South Wales and colleagues report their findings in a recent issue of PLoS ONE.
"We show that the treatments that spread are not necessarily those that are most efficacious at curing the ailment," the researchers say.
Even where there is a lot of evidence available on treatments, people are not necessarily able to get access to this immediately, says Tanaka, who models biological systems.
"Instead of asking the question of whether particular treatments were working or not working, we were interested to ask under what conditions would any treatment spread in a population," says Tanaka.
He and colleagues used mathematical modelling of what is called "social learning", where people see others using a treatment and copy them, as happens in the animal world.
"If you look at chimp populations they often observe each other and pick up new ways of doing things such as eating rough leaves that get rid of parasites in their gut," says Tanaka.
He says whether good treatments versus bad treatments spread depend on two opposing forces.
On the one hand people can abandon a treatment that doesn't appear work and stop it from spreading.
On the other they can persist in using it in the hope it will work, there by using it longer so more people give it a go.
"So there are both of these forces at work," says Tanaka.
He says where people persist in using bad treatments, perhaps because they've invested a lot in it already, this favours the spread of these treatments.
Tanaka says that the modelling could help explain why ineffective folk or complementary remedies continue to be used.
He says judging whether a treatment is effective or not can be difficult, especially when there is a lack of evidence available.
And he says this can apply to modern Western treatments as well.
Associate Professor Alex Barratt at the University of Sydney who has studied the poor uptake of evidence-based medicine describes Tanaka's paper as "really interesting".
"There are so many examples of where the effective treatment [for an illness] has taken 20 or 25 years to get into broad practice, so clearly there are factors that we don't understand going on."
"Maybe this paper is a little step in the direction of trying to understand what those things are."
Barratt says the paper shows a range of subjective factors influence individual judgements about whether a treatment works or not.
But, she says, history has shown that individuals aren't in a position to judge whether a treatment works or not.
Barratt gives the example of one heart drug used in the US in the 1980s.
"There was a really good biological rationale for using it, but the clinicians prescribing those medicines couldn't actually see that they were killing people with these drugs," she says.
"It wasn't until they did a big randomised controlled trial that it was really obvious that the drugs were doing more harm than good."