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NIDA. (2018, March 12). Say What? “Placebo”. Retrieved from

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The NIDA Blog Team
March 12 2018

"Say What?" is a periodic series in which we define scientific terms and explain their importance.

Why would a researcher give someone a pill when the researcher knows the pill will have no effect on that person? Sounds pointless, right? But there can be an important reason.

Before a drug is approved to treat a health condition, it’s tested many times to be sure it works and is safe to use. During these tests, a researcher often uses a placebo. A placebo looks like a real drug (a pill, for instance), but unlike a real drug, it doesn’t contain active ingredients. In fact, a placebo pill might be made of sugar.

Which one’s real?

So, how do scientists use a placebo? Consider this scenario: A scientist wants to test how well a medication helps someone quit smoking. To figure that out, they’ll set up a study and randomly assign some people to take the real drug and others to take a placebo. Only the scientist knows who’s getting the real drug. And sometimes, even the scientist doesn’t know; this is called a “double-blind” study.

The scientist then compares how both groups reacted to the pills. If there’s no difference, the drug probably didn’t work the way it was supposed to. If there is a difference (and depending on several other factors), it may justify further study.

“Placebo effect”

Sometimes a person will seem to be affected by a placebo. The term “placebo effect” refers to a positive response someone feels after they take a placebo, simply because they expect to feel something when they take a pill. Pretty interesting, huh?

Placebos are used in all types of studies, including ones about treating addiction and developing medications for opioid use disorder. So, that’s how a pill that causes no effects can make a big difference.

Learn about another important part of scientific research: data.