Why do placebos work? Scientists identify key brain pathway
Study finds opposite impacts on brainstem of placebo and “nocebo” effects
Daryl Austin on Science.org, Oct 2021
(from the article)
“The placebo effect can bring powerful relief—but what does that look like in your brain? A new study finds fake therapies and fake side effects have a real impact on your brainstem, a hub of pain processing, affecting it in opposite ways. The work could help scientists develop better treatments for chronic pain.
It’s “a major rigorous contribution to the field,” says Ted Kaptchuk, a biomedical scientist at Harvard Medical School who was not involved with the study. Still, he cautions that more work is needed to see whether this laboratory-based study translates to the real world.
Scientists have known about the placebo effect for more than 400 years. In 1572, a French philosopher wrote that “there are men on whom the mere sight of medicine is operative.” Yet researchers have struggled to understand why patients given a nonactive therapy such as a sugar pill still feel relief. They’ve also been confounded by the opposite phenomenon: When patients are told a placebo has harmful side effects, they often feel bad afterward—the so-called “nocebo” effect.
To find the signature of these two effects in brain, researchers brought 27 participants—13 men and 14 women with an average age of 23—into their laboratory at the University of Melbourne. The scientists strapped a device called a thermode to their arm, which heated up to a moderately painful temperature. Afterward, the researchers told the participants they were applying one of three creams to the affected area: a pain reliever, a pain inducer (which would make the heat feel worse), and a control cream with no effect. In reality, all three substances were petroleum jelly.
All the while, the team scanned the volunteers with a high-resolution functional magnetic resonance imaging (fMRI) machine to detect which parts of their brain were most active. Most participants in the study experienced either the placebo or nocebo effect. About one-third reported lower levels of pain when the “pain reliever” was applied, whereas slightly more than half reported more pain when the “pain inducer” was applied…”
