The first time the placebo effect really got under my skin was when I read that roughly one-third of people with irritable bowel syndrome improve on placebo treatments alone. Usually this statistic is presented as a fascinating quirk of medicine. My reaction was anger.
Humanity possesses an extremely effective treatment, with essentially zero side effects – and patients need someone else’s permission to use it.
The placebo effect refers to the improvements in symptoms that patients experience after they’re given an inert treatment like a sugar pill. Driven by expectation, context and social cues rather than pharmacology, the placebo effect is often dismissed as all in the mind. But decades of research have shown it is anything but imaginary.
Placebo treatments can trigger measurable changes in the brain, immune system and hormone function. In studies on pain, placebos cause the brain to release endorphins, the body’s natural opioids. In Parkinson’s disease, placebo injections increase dopamine activity in the brain. The placebo effect isn’t magic. It’s biology.
Having spent nearly a quarter-century teaching evolutionary medicine, I’ve come to see placebos not as curiosities of clinical trials but as windows into how human biology responds to social signals. And it’s that relationship that is exactly what makes the placebo effect unsettling.
Medicine works, even when it isn’t medicine
The placebo effect is so reliable that researchers must account for it in nearly every clinical trial.
When testing a new drug, scientists compare its effects to what patients experience on a placebo treatment like sugar pills, saline injections or sham surgery. If the drug doesn’t outperform the placebo, it rarely reaches the public. Placebo responses are common and powerful enough to rival active treatments.
Even surgery isn’t immune to the placebo effect. In several well-documented studies of knee procedures, patients who received sham operations – incisions without the full surgical repair – improved almost as much as those who received the real procedure.
The experience of going under the knife can itself be healing.
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Clearly something real is happening inside the body. But the strangest part of the placebo effect is not that it works. It’s what makes it work.
The prescription of belief
Placebo treatments tend to be more effective when delivered by credible authorities. Pills work better when prescribed by doctors wearing white coats. Expensive pills outperform cheap ones. Injections produce stronger responses than tablets.
Some researchers have even removed the deception from placebo experiments entirely. In open-label placebo studies, patients are directly told they are receiving a placebo; and yet many still report significant improvement.
But look more closely at how these studies are run. Patients are not simply…
