Study Finds Placebo Effect a Mirage
Challenges mind-over-body influence
WEDNESDAY, May 23, 2001 (HealthDayNews) -- Is the placebo effect an illusion?
A new Danish study, appearing in the the May 24 issue of the New England Journal of Medicine, says placebos are at best only marginally useful at improving symptoms, despite their widespread reputation to the contrary.
The word placebo comes from the Latin "I will please." Studies have suggested that placebos -- like sugar pills, sham surgery or other medical head-fake -- can produce dramatic improvements in symptoms for patients with heart ailments, depression and everything in between.
In the latest work, Drs. Asbjørn Hróbjartsson and Peter Gøtzsche of the University of Copenhagen reviewed 114 studies, involving roughly 8,500 patients. They compared pharmacological, physical or psychological placebos to the absence of placebo with observation or standard therapy.
Conditions ranged from high blood pressure to infertility. The researchers measured outcomes by whether the treatment worked or not and by continuous, more subjective gauges such as prolonged control of pain.
In 32 yes-no trials, smaller studies were more likely to show a positive placebo effect. Yet overall, placebo therapy wasn't more effective than the lack of it, the researchers say.
Placebos did appear to be modestly effective in the 82 continuous outcome trials. However, the benefits shrank as the size of the studies grew, suggesting that the scientists who conducted the smaller-scale research may have injected bias into their analysis of the results, say the researchers.
Pain did respond to placebo by an average of about 6.5 millimeters on a 100 millimeters visual scale, the study found. The researchers say that's not bad, but it's only about a third of the difference in effect between non-steroidal anti-inflammatory drugs and sham treatment.
"We found little evidence that placebos in general have powerful clinical effects," the researchers write. "We found significant effects of placebo on continuous subjective outcomes and for the treatment of pain, but also bias related to larger effects in smaller trials."
The authors conclude: "The use of placebo outside the aegis of a controlled, properly designed clinical trial cannot be recommended."
Dr. John Bailar III, professor emeritus at the University of Chicago and author of an editorial accompanying the journal article, says the Danish study "shifts the burden of proof" away from the assumption that placebos work. "People who say there is a placebo effect are going to have to produce evidence of that," he says.
Earlier studies that found placebo effects generally compared sham treatment to a drug or other intervention, Bailar says. Yet disease symptoms often tend to drift from bad to somewhat better, so it's impossible to tell if patients improved by taking the placebo or because the ailment went its normal way, he says.
Bailar says mind-body interactions have been "grossly overstated." Though he says he's not ready to discard placebos yet, particularly in clinical trials, he say he would like to see them used less in everyday practice.
"I think most doctors prescribe placebos most days, drugs they know very well have virtually no chance of producing any beneficial effect," Bailar says. He cites the example of a doctor who gives his patient an antibiotic for a cold, knowing the drug will have no effect on the virus that causes the symptoms.
Although in some cases the practice is benign, using placebos might discourage both patient and physician from seeking a better therapy, Bailar says. It can also be costly and carry side effects. "The thing that bothers me most is the effect of placebos on the relationship of the doctor with the patient. It's basically a kind of deception," Bailar says.
But Daniel E. Moerman, an anthropologist and placebo expert at the University of Michigan in Dearborn, says the study may have failed to find an effect from sham therapy because it neglected to consider the paradoxical impact of no therapy.
"There is no such thing as a non-treated control," says Moerman. "People who get non-treatment are told there's nothing wrong with them. That's a significant kind of engagement." Patients in non-treatment arms of studies also are often asked to keep diaries of their symptoms, a process he considers "the minimal form of psychotherapy."
What To Do