Placebo effect in treating colds

People who believe a cold remedy will work may indeed feel better sooner – even if they don't get the real treatment, a new study suggests.

Researchers say their findings are evidence that the so-called placebo effect is at work in recovery from the common cold. So, if treatments like chicken soup and vitamin C are unlikely to do any harm, patients might as well stick with them, they say.

For the new study, reported in Annals of Family Medicine, researchers focused on the common cold – which famously has no cure.

Testing the placebo against Echinacea

They randomly assigned 719 people with the beginnings of cold symptoms to one of four groups.

In one group, people were given the herbal cold remedy Echinacea and knew they were taking it. Two other groups were given either Echinacea or a placebo, but participants did not know which they were taking. The fourth group received no pills of any kind.

Overall, there were no significant differences among the groups when it came to the severity or duration of symptoms – which lasted about a week in all cases.

But then the researchers focused on the 120 people who, upon entering the study, gave high ratings to Echinacea's effectiveness.

Echinacea works faster

In that group of Echinacea believers, those who were given pills – Echinacea or placebo – felt better faster. Placebo users recovered a full 2.5 days sooner than their no-pill counterparts, while Echinacea users were cold-free about 1.5 days sooner.

"That's actually a huge difference," said lead researcher Dr Bruce Barrett, of the University of Wisconsin in Madison.

"No treatment out there has ever been shown to reduce the duration of colds," he said. He said the findings offer more evidence that "what people believe about their medicines matters".

Watch for effects in Echinacea

As for Echinacea itself, studies have come to conflicting conclusions about whether it really works. In an analysis of this same study group, Dr Barrett's team found that (as in this analysis) Echinacea users in general fared no better than the placebo or no-pill groups.

But there was also no evidence that the Echinacea group suffered side effects at a higher rate. And if a patient has used Echinacea and believes it eases the misery of a cold, it would seem reasonable to continue, according to Dr Barrett.

(Reuters Health, July 2011)

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