Why Placebos Work Wonders
Say "placebo effect" and most people think of the boost they may get
from a sugar pill simply because they believe it will work. But more and
more research suggests there is more than a fleeting boost to be gained
from placebos.
A particular mind-set or belief about one's body or health may lead
to improvements in disease symptoms as well as changes in appetite,
brain chemicals and even vision, several recent studies have found,
highlighting how fundamentally the mind and body are connected.
It doesn't seem to matter whether people know
they are getting a placebo and not a "real" treatment. One study
demonstrated a strong placebo effect in subjects who were told they were
getting a sugar pill with no active ingredient.
Placebo treatments are sometimes used
in some clinical practices. In a 2008 survey of nearly 700 internists
and rheumatologists published in the British Medical Journal, about half
said they prescribe placebos on a regular basis. The most popular were
over-the-counter painkillers and vitamins. Very few physicians said they
relied on sugar pills or saline injections. The American Medical
Association says a placebo can't be given simply to soothe a difficult
patient, and it can be used only if the patient is informed of and
agrees to its use.
Researchers want to know more about how the placebo effect works, and
how to increase and decrease it. A more powerful, longer-lasting
placebo effect might be helpful in treating health conditions related to
weight and metabolism.
Hotel-room attendants who were told they were getting a good workout
at their jobs showed a significant decrease in weight, blood pressure
and body fat after four weeks, in a study published in Psychological
Science in 2007 and conducted by Alia Crum, a Yale graduate student, and
Ellen Langer, a professor in the psychology department at Harvard.
Employees who did the same work but weren't told about exercise showed
no change in weight. Neither group reported changes in physical activity
or diet.
Another study, published last year in
the journal Health Psychology, shows how mind-set can affect an
individual's appetite and production of a gut peptide called ghrelin
(GREL-in), which is involved in the feeling of satisfaction after
eating. Ghrelin levels are supposed to rise when the body needs food and
fall proportionally as calories are consumed, telling the brain the
body is no longer hungry and doesn't need to search out more food.
Yet the data show ghrelin levels depended on how many calories
participants were told they were consuming, not how many they actually
consumed. When told a milkshake they were about to drink had 620
calories and was "indulgent," the participants' ghrelin levels fell
more—the brain perceived it was satisfied more quickly—than when they
were told the shake had 120 calories and was "sensible."
The results may offer a physiological explanation of why eating diet
foods can feel so unsatisfying, says Ms. Crum, first author on the
study. "That mind-set of dieting is telling the body you're not getting
enough."
Studies across medical conditions including depression, migraines and
Parkinson's disease have found that supposedly inert treatments, like
sugar pills, sham surgery and sham acupuncture, can yield striking
effects. A 2001 study published in Science found that placebo was
effective at improving Parkinson's disease symptoms at a magnitude
similar to real medication. The placebo actually induced the brain to
produce greater amounts of dopamine, the neurotransmitter known to be
useful in treating the disease.
At times, a weaker placebo effect might be desired. In trials of
experimental drug treatments for dementia, depression and other
cognitive or psychiatric conditions, where one patient group takes
medication and the other takes a sugar pill, it can be difficult to
demonstrate that the medicine works because the placebo effect is so
strong.
With depression, an estimated 30% to 45% of patients—or even more, in
some studies—will respond to a placebo, according to a review published
in December in Clinical Therapeutics. An additional 5% of patients were
helped by an antidepressant in cases of mild depression, and an
additional 16% in cases of severe depression. (The clinically meaningful
cutoff for additional benefit was 11%.)
Fertility rates have been found to improve in women getting a
placebo, perhaps because they experience a decrease in stress. A recent
randomized trial of women with polycystic ovarian syndrome found that
15%, or 5 of 33, got pregnant while taking placebo over a six-month
period, compared with 22%, or 7 of 32, who got the drug—a statistically
insignificant difference. Other studies have demonstrated pregnancy
rates as high as 40% in placebo groups.
Ted Kaptchuk, director of Harvard's Program in Placebo
Studies and the Therapeutic Encounter, and colleagues demonstrated that
deception isn't necessary for the placebo effect to work. Eighty
patients with irritable bowel syndrome, a chronic gastrointestinal
disorder, were assigned either a placebo or no treatment. Patients in
the placebo group got pills described to them as being made with an
inert substance and showing in studies to improve symptoms via
"mind-body self-healing processes." Participants were told they didn't
have to believe in the placebo effect but should take the pills anyway,
Dr. Kaptchuk says. After three weeks, placebo-group patients reported
feelings of relief, significant reduction in some symptoms and some
improvement in quality of life.
Why did the placebo work—even after patients were told they weren't
getting real medicine? Expectations play a role, Dr. Kaptchuk says. Even
more likely is that patients were conditioned to a positive
environment, and the innovative approach and daily ritual of taking the
pill created an openness to change, he says.
Do placebos work on the actual condition, or on patients' perception
of their symptoms? In a study published last year in the New England
Journal of Medicine, Dr. Kaptchuk's team rotated 46 asthma patients
through each of four types of treatment: no treatment at all, an
albuterol inhaler, a placebo inhaler and sham acupuncture. As each
participant got each treatment, researchers induced an asthma attack and
measured the participant's lung function and perception of symptoms.
The albuterol improved measured lung function compared with placebo. But
the patients reported feeling just as good whether getting placebo or
the active treatment.
"Right now, I think evidence is that placebo changes not the
underlying biology of an illness, but the way a person experiences or
reacts to an illness," Dr. Kaptchuk says.
Placebo can be more effective than the intended treatment. In a trial
published in the journal Menopause in 2007, 103 women who had
menopausal hot flashes got either five weeks of real acupuncture, or
five weeks of sham acupuncture, where needles weren't placed in accepted
therapeutic positions. A week after treatments ended, only some 60% of
participants in both groups reported hot flashes—a robust immediate
placebo effect. Seven weeks post-treatment, though, 55% of patients in
the sham acupuncture group reported hot flashes, compared with 73% in
the real acupuncture group.
Corrections & Amplifications
An earlier version of this article said that a study in the journal Health Psychology about appetite and the gut peptide ghrelin was published earlier this year.
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