Blog | Thursday, July 14, 2011

QD: News Every Day: Believing in placebos?

Two new studies out this week examine the power of the placebo effect.

A double-blind, crossover pilot study published in today's New England Journal of Medicine examined 39 patients with asthma randomly assigned to receive active treatment with an albuterol inhaler, a placebo inhaler, sham acupuncture, or nothing. Each patient received one of these interventions in random order at four sequential visits scheduled three to seven days apart. The "block" scheduling was repeated twice, so that each patient made a total of 12 visits. Maximum forced expiratory volume in 1 second was measured at each visit with spirometry, and patients self-reported improvement ratings. Although albuterol increased maximum forced expiratory volume in 1 second by 20% compared with 7% for each of the other interventions, patients often couldn't tell the difference: Their self-reported improvement ratings were similar regardless of which intervention they received, and were statistically significantly greater than patients in the no-intervention group (50% for albuterol, 45% for placebo, 46% for sham acupuncture, 21% for no intervention).

In a randomized, controlled trial published in the July/August Annals of Family Medicine, researchers assigned 719 patients who'd just come down with the common cold to receive no pills, blinded placebo pills, blinded echinacea pills, or open-label echinacea pills. People who didn't take pills tended to be sicker longer, but patients who did and who believed echinacea would help their cold symptoms had shorter, less severe illness---even if they were assigned to placebo.

Both studies had limitations, including lack of information on severity of subjective symptoms in the former and lack of information on potential causal associations in the latter. But both trials offer interesting ideas about how placebos may help and hurt in clinical practice.

"The data shown here suggest that those who believe in echinacea's effectiveness may gain the most benefit from being randomly assigned to echinacea (or a pill that might be echinacea)," the authors of the Annals of Family Medicine study wrote. "We suspect that larger placebo effects are derived when a person chooses his or her own treatment rather than have it randomly assigned."

Meanwhile, according to the authors of the New England Journal of Medicine study, clinicians perhaps shouldn't stake too much faith on asthma patients' self-reports of improvement. "Many patients with asthma have symptoms that remain uncontrolled, and the discrepancy between objective pulmonary function and patients' self-reports noted in this study suggests that subjective improvement in asthma should be interpreted with caution and that objective outcomes should be more heavily relied on for optimal asthma care," they wrote.