Scientists Say: Placebo

This is a substance or procedure that is supposed to have no medical effect

a small glass beaker full of pills of different shapes, sizes and colors

When scientists want to find out if a new pill for pain works, they may compare it against a placebo — a pill that doesn’t have any painkiller in it.

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Placebo (noun, “Plah-SEE-bo”)

A placebo is a substance or procedure that is supposed to have no medical effect. Placebos are often used in clinical trials to help scientists figure out if a new medicine or treatment works. Some people in the trial are given the new drug — say, a new pill to kill pain. Others are given a placebo — a pill that has no medicine in it. The volunteers will not know which pill they took. Scientists can then compare results from people who received the new painkiller to those who got the placebo. That can show them how well the new drug works.

Sometimes placebos produce an outcome similar to the treatment it is being compared to. That’s because what we believe often influences what we feel. Taking a placebo for pain, for example, will often make people feel less pain. A reactions like this — where a placebo produces some outcome even though there was no active medicine in it — is known as the placebo effect.  

Many people might think of pills when they think of placebos. But placebos can also include treatments. For example, some scientists study acupuncture. That’s a therapy that stimulates points on someone’s body with needles. But to study it, the placebo group may also have needles stuck into them — just not in the same places. 

In a sentence

When testing a new treatment for cat allergies, some volunteers got an injection of the new treatment, while others got a placebo.

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Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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