A Little Placebo Effect For the Common Cold
In the fight against the common cold, a patient's feelings about a treatment could be a helpful weapon.
A study of more than 700 patients found cold sufferers who get a pill, regardless of what it contains, have less severe symptoms and recover a bit sooner than patients who don't take pills.
The placebo effect was most pronounced among people who believed in echinacea's healing properties.
The findings by researchers at the University of Wisconsin, Madison will be published in the July/August edition of the Annals of Family Medicine. The study was primarily funded by the National Institutes of Health.
The 719 participants, ages 12 to 80, with new colds were divided into four groups. One group didn't receive anything. Another group received echinacea and were told they were receiving the herb. Two other groups received pills but didn't know the contents: The pills either contained echinacea or were a placebo.
At the time the study was designed, some studies suggested echinacea had a benefit in treating colds. More recent studies, including previous findings from the Wisconsin cold study, suggest echinacea has little to no impact.
Those receiving pills were instructed to take two pills four times a day for the first 24 hours and then continue with one pill four times a day for four days. During the study, virus samples were obtained from a person's nose. People were required to complete a survey twice a day to assess the severity of their illness. Participants were also asked about their beliefs in echinacea as a potential cold treatment.
Overall, researchers didn't find major differences between the four groups, but the length and severity of colds was slightly worse among patients who didn't receive pills. Colds lasted about six to seven days in all groups.
There was little difference between those who didn't know they were receiving echinacea and those who knew they were taking echinacea, which suggests the herb didn't have a major impact.
However, a subgroup who rated echinacea's effectiveness highly on a form at the start of the study—and were given a placebo during the study—had the shortest duration colds. Their illnesses were 2½ days shorter than those who weren't taking pills.
The study also found 62% of patients who didn't receive pills reported headaches compared with less than 50% of patients in the other three treatment groups.
Researchers concluded that there can be a placebo effect with the common cold, particularly in people who believe in a therapy, but the effect is "limited" and "not large."