It may not take much to tame a nagging cough -- in fact, merely believing that a certain treatment will suppress a cough may do the trick, according to new Australian research.
The Daily Mail reported that people in a very small Australian study who received a placebo instead of a drug had less of an urge to cough after inhaling capsaicin, an ingredient found in chili peppers, than people who received no treatment at all.
Researchers told participants that they were going to inhale either lidocaine, a common anesthetic, to minimize the urge to cough; or a gas, which they were told would not work. In actuality, however, all study participants received the ineffective gas.
The finding that people who thought they received the lidocaine had 45 percent less of an urge to cough than those who knew they were receiving an ineffective treatment surprised researchers, who have long known about the so-called placebo effect, but didn't expect it to be that strong.
"It's difficult to know why that is that cough responds so well to placebo," lead author Stuart Mazzone told the newspaper. Placebos are more effective for coughing than for other conditions, including pain, he said.
"As a physician, the more the placebo effect works, the better," said Dr. Mark Stacy, vice dean for clinical research at Duke University Medical Center. "The more benefit a patient would have, the better."
Placebos seem to bring about a complex response in the brain, said Dr. Charles Raison, an associate professor of psychiatry at the University of Arizona College of Medicine.
"It's probably a combination of therapeutic reliance, hope and expectation, and when the brain perceives them, it is able to change activity in circuits relevant to the condition," he said.
Despite the positive effects research has uncovered, it is unethical for doctors to prescribe placebos without informing patients they're doing it.
And the placebo effect doesn't just work on coughs, experts say. Studies suggest that placebos also bring about positive effects in the conditions on the next few pages.
"In Parkinson's disease, placebos increase levels of dopamine in the brain where there are deficits," Raison said.
In a landmark 2007 study, researchers from the University of British Columbia gave one group of Parkinson's patients a placebo and gave a second group a drug called apomorphine, which mimics the effects of dopamine. Dopamine is a brain chemical associated with pleasure and reward-seeking behavior; it also controls muscle movements. A deficiency of dopamine is a characteristic of Parkinson's.
"Some patients were injected with apomorphine and others were injected with a placebo," said Stacy. "Lo and behold, patients who received the placebo actually released dopamine."
The expectation of receiving a drug, he explained, resulted in the release of dopamine by the brain.
While the placebo effect does lead to improvement, drugs are generally more effective.
"Even though the symptoms can improve with placebo alone, the effects are not as good as with drugs," said Dr. Walter Brown, a clinical professor of psychiatry at Brown University and Tufts University School of Medicine.
"Some pain problems seem to do as well with placebo as with real pain medication," said Brown, also the author of "The Placebo Effect in Clinical Practice."
Pain that causes a great deal of distress seems to be more responsive than other kinds of pains, he said.
But in other cases, people may get only about half as much pain relief as they do from drugs.
The effect can be complex and involve other factors in some cases. Stacy noted one study that examined the placebo effect on people who first received electric shock, followed by placebos disguised as pain medications. Some participants were told the placebos cost one amount and others were told they cost more.
"Both groups improved, but those who received the placebo believed to be more expensive reported feeling better than those who received the cheaper one," Stacy said.
|Depression and Anxiety|
Depression is also a condition often improved by placebo almost as much as by medications.
A 2010 study published in the Journal of the American Medical Association found that for mild or moderate depression, selective serotonin reuptake inhibitors (SSRIs), commonly used antidepressants, were no more effective in treating symptoms than placebo. For severe depression, however, the drugs worked better.
Another recent study found that there were no differences in terms of brain changes between study subjects who took antidepressants versus those who took a placebo.
"Placebos activate the same pathways in the brain that antidepressants do," said Raison.
"We don't know how placebos bring about changes, but they do," said Brown.
Most anxiety disorders respond well to placebos as well, he added. Drugs are slightly more effective, but many people feel better with just placebo.
A number of studies have demonstrated that just the sight of a nebulizer, a device used to administer asthma medication, can relieve symptoms.
"If you treat asthma with nebulizers and people get asthma relief because of a drug that opens up airways, it's been shown that just the nebulizer itself can give the same effect," Brown said.
Brown attributed this effect to classical conditioning, a process that involves a person's automatic response to a stimulus.
"The nebulizer becomes associated with the relief of airway constriction, so just looking at it can lead to relief. The placebo effect works quite well."
|Irritable Bowel Syndrome|
Irritable bowel syndrome (IBS) is a condition characterized by abdominal pain, diarrhea, bloating and other gastrointestinal distress.
Despite the symptoms, there are no bowel abnormalities.
"Placebo worked quite well in studies to relieve the symptoms," Brown said.
In one study, researchers found that administering a placebo without hiding the fact that it was a placebo still led to more improvement than no treatment at all.
"Placebos administered without deception may be an effective treatment for IBS," wrote the authors, led by Ted Kaptchuk of Harvard Medical School. "Further research is warranted in IBS, and perhaps other conditions, to elucidate whether physicians can benefit patients using placebos consistent with informed consent."