Dan Ariely of Duke University in North Carolina won an Ig Nobel prize last week for showing that expensive placebos work much better than cheap ones. People who believed that the pills they were given cost $2.50 each reported feeling less pain from a series of electric shocks than people who thought their pills had been discounted to 10 cents each.
The Ig Nobels are traditionally meant to celebrate humorous but essentially pointless science – other winners this year included researchers who had proved that Coca-Cola douches do not provide effective contraception and University of New Mexico psychologists who proved that lapdancers make more tips when in the most fertile periods of their menstrual cycle.
However, the placebo research is far from pointless. It illustrates a point that leading researchers are only just beginning to acknowledge, and could have implications for clinical practice, the regulation of complementary medicines and the way we conduct clinical trials of pharmaceuticals.
We have long known that belief and expectation play a powerful role in the biochemistry of the human body, but the placebo effect is a much more powerful and mysterious phenomenon than we have been led to believe.
As I outlined in 13 Things…placebo researchers have learned, for instance, that diazepam doesn't reduce anxiety in patients after an operation unless they know they are taking it (it's not yet clear if this is also true of diazepam's other effects). National Institutes of Health researchers have shown that cocaine abusers who know they are receiving the drug can get by on half the amount required by those given a covert dose. If you don't tell people that they are getting an injection of morphine, you have to inject at least 12 milligrams to get a painkilling effect, whereas if you tell them, far lower doses can make a difference. This has obvious implications for the way we run clinical trials.
It turns out that Ariely (check out his web page here – it’s crazy and intelligent stuff) may not even have needed to deceive his subjects into thinking they were getting a medicine at all, whether cheap or costly. It is possible to bypass common sense with the placebo effect. When, as part of research for 13 Things… I asked researchers to elicit a placebo response in me, they had no trouble doing it. Even though I knew I was being tricked, the placebo conditioning procedure still allowed me – like Ariely’s subjects – to experience a series of electric shocks as nothing more than a light touch on the arm. (I blogged about this for New Scientist here.)
This is a potentially useful discovery, allowing doctors to bypass the ethical problems of deceiving patients. Researchers at the University of North Carolina have shown, for instance, that ADHD-affected children can manage on reduced stimulant medication – reducing side-effects – when given a placebo. The twist is, the children, the doctors and the parents all knew they were using something with no active ingredient, but it worked anyway. Such “open-label” use of placebos holds great potential for improving health care, the researchers say.
Ariely’s findings could help lay to rest one of the great arguments of modern science: whether homeopathic remedies and other complementary medicines have any medical benefit above placebo. Science has struggled with the question because there are indications in the literature that these interventions do have some effect beyond what the placebo effect can explain. But now that we are beginning to understand that placebo response depends on previously unexplored factors like perceived cost of the medicine (and homeopathic medicines are certainly not cheap), perhaps we can find a way out of this quagmire.
Add in the idea that some chemicals are only efficacious when in contact with the chemicals our bodies produce when we have our hopes raised, and we start to see that we have some seriously murky waters to explore before we can claim to understand how and why many medical interventions work – or don’t. The placebo effect is not at all as we have imagined. And it is certainly not that funny.
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