Placebo effect quantified: Half a real drug's effect can be reduced by disbelief

The study found that drugs proven to be clinically effective could be rendered less effective with the mere thought that it was a placebo.
Posted By Ananth Baliga  |  Updated Jan. 10, 2014 at 5:56 PM
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The placebo effect is well known, but a new study has quantified it, and found that about half of a real drug's effect can be reduced by the belief that it's a placebo.

Migraine patients given placebos and told it was a popular drug had the same outcomes as people who were given the actual drug and told it was a placebo, calling pharmacological effectiveness into question.

The study conducted at the Beth Israel Deaconess Medical Center and other Boston hospitals showed that half a drug's effect comes from the patient's expectation that it could be used to treat their illness, even one with subjective experiences.

"There was no difference between the pharmacology of the drug in reducing pain and the placebo dressed up with a nice word," said study author Ted Kaptchuk. "Basically we show that words can actually double the effect of a drug. That's pretty impressive."

Researchers used 66 patients and tested them during seven successive migraine attacks. They chose migraines because there already exists an effective drug, Maxalt, that has been shown to work better than placebo pills.

Patients were given six envelopes containing pills for the next six migraines. Two were marked Maxalt, two were marked placebo, and two were marked as unknown. Patients then rated the level of pain experienced two hours after every consequent attack.

When they took a placebo correctly labeled as a placebo they experienced a 26 percent drop in pain and a 40 percent drop when taking the Maxalt pill marked as Maxalt. When they weren't told what the pill was, they again experienced a 40 percent drop in pain.

But when given Maxalt labeled as a placebo or a placebo labelled as Maxalt the decrease in pain was almost the same.

"There's something going on here that we don't understand," Kaptchuk said. "But I think uncertainty engages you in a different way." He adds that doubt may strengthen the desire to believe.

Patients were not influenced by a doctor or researcher about the pills, as they did not interact with them through the course of the trial. The findings are published in Science Translational Medicine.

[Beth Israel Deaconess Medical Center] [NPR] [Science Translational Medicine]

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