Asthma study reveals the power of the placebo effect

The placebo effect is alive and well, at least for patients with acute asthma.

That’s the finding of a pilot study funded by the National Center for Complementary and Alternative Medicine -- part of the National Institutes of Health -- and published in Thursday’s edition of the New England Journal of Medicine.

Researchers from Harvard Medical School and colleagues decided to test the placebo effect in asthma patients because it’s easy to assess their physical improvement (as measured by lung function tests) in a short period of time.

They recruited 39 patients who cycled among four treatment options over 12 visits. In some cases they got albuterol -- a bona fide asthma treatment -- through an inhaler, and sometimes they used an inhaler with no medicine, though the subjects didn’t know which was which. Other times, they were given sham acupuncture treatment (but told it was real), and on some visits there was no treatment at all.

Patients said their symptoms improved by 21% on the occasions when they got no treatment. But when they thought they were getting some kind of treatment, they said their symptoms improved much more -- by 50% when they got the albuterol, by 45% when they had the placebo inhaler, and by 46% with the sham acupuncture. (There was no statistically significant difference among those three outcomes.)

Did they really get that much better? When they had the albuterol, patients’ maximum forced expiratory volume in 1 second (a measure of lung function) improved by 20%. But in all three other cases, lung function improved by only 7.1% to 7.5%.

The results demonstrate that the placebo effect is powerful, the researchers said. When it came to patients’ assessments of the treatments, “the placebo effects were equivalent to the drug effect,” they wrote.

These results also suggest that patients can’t be relied upon to make accurate reports of whether their symptoms are getting better. In this study, patients couldn’t tell when the albuterol was making a real difference. In fact, any time they got something that looked like a “treatment,” they reported roughly the same degree of improvement, the researchers said.

“Even though there was a large, objective drug effect ... that was nearly three times the effect of the two placebos and the no-intervention control ,” they wrote, “patients could not reliably detect the difference between this robust effect of the active drug and the effects of inhaled placebo and sham acupuncture.”

A summary of the study is available here.