Why Placebos Really Work

July 20, 2016

Scientists are finding a growing number of ways placebos appear to bring about real health benefits in patients.

The research could someday lead to increased use of placebos—substances that have no apparent pharmaceutical effect—in treatments for common diseases.

Studies have shown that administering placebos reduces pain and symptoms in patients with irritable bowel syndrome and migraines, even when patients know they are taking a placebo. Scientists are exploring if they can get the same result in chronic back pain and cancer-related fatigue.

Parkinson’s-disease researchers discovered that stopping patients’ real medication and substituting a placebo continues to ease their symptoms, likely because the body is preconditioned to trigger the same response.

Numerous studies have documented neurobiological effects that placebos have in the brain, resulting in the release of neuromodulators that can help reduce pain and symptoms of illness. New evidence suggests the fake drugs may also affect the body, in particular the immune system, according to an animal study published online in July in the journal Nature Medicine.

“This is not just making it up in your mind. The placebo effect has a biology,” says Ted J. Kaptchuk, director of the Program in Placebo Studies and Therapeutic Encounter at Beth Israel Deaconess Medical Center in Boston and a professor at Harvard Medical School. “The pathways that we know the placebo effects use are the pathways many significant drugs use.”

Placebos are most commonly used in clinical drug trials, paired off against a new drug being developed. A surprisingly large number of doctors—studies and surveys suggest at least half—prescribe placebos to their patients. This is usually when there isn’t a suitable remedy on the market for a patient’s symptoms or the symptoms don’t seem to be a serious threat, such as fatigue or minor aches.

The placebos doctors most often prescribe are active drugs but in such low doses that there is no apparent therapeutic benefit, says Walter Brown, a clinical professor of psychiatry at Brown University who wrote “The Placebo Effect in Clinical Practice,” a book published in 2013. Physicians also prescribe vitamins, antibiotics or over-the-counter analgesics, like aspirin. Doctors rarely will prescribe an outright sugar pill.

Guidelines from the American Medical Association from 2006 tell doctors it is unethical to give patients a placebo without disclosing it to them. But few doctors are believed to actually do this, experts say.

Dozens of studies have shown that the power of placebos goes beyond patients’ imaginations, says Prof. Kaptchuk, of Beth Israel Deaconess. This was first demonstrated in 1979 when patients in a dental-pain experiment were given a placebo they thought was a painkiller, he says. About one-third of them reported less pain. Subsequent drugs to block the action of painkillers removed the placebo effect.

The study showed placebos cause the brain to release endogenous opioids, or endorphins, that reduce pain, Prof. Kaptchuk says. Subsequent research has found that other substances are also activated by placebos, including endocannabinoids and dopamine, part of the brain’s reward system.

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