Can you explain what the “placebo effect” means?


In previous columns you’ve mentioned something called the “placebo effect.” Can you explain what that means?


A placebo is a pill or other treatment that is inactive. It may look identical to a real drug, but it doesn’t really have the drug in it. It’s also called a “sugar pill,” although the inactive substances in it don’t include table sugar.

Researchers use placebos in clinical studies. They compare the results for a group of people who got an active treatment with the results for a group of people who got the placebo treatment. Typically, neither the people in the study nor their doctors know if they are taking the real medicine or the placebo until after the study is ended. This is how researchers can tell how well a treatment worked.

Even when people taking the real drug do better than the people taking the placebo, something interesting often happens: The people taking the placebo sometimes report that they also feel better since they started taking it.

For many years, most of us in the medical profession assumed such people were just imagining that they were feeling better. After all, the placebo pill contained no active substance that could affect the chemistry of the body. We called it the “placebo effect.”

What’s behind that effect? When real medicines work, they often do so by supplying a chemical that is missing in the body. However, they also sometimes stimulate natural healing powers.

Take pain, for instance. Like all symptoms, pain is experienced in the brain. It also can be treated by the brain. Endorphins are brain chemicals that are naturally released when a person experiences pain, reducing its intensity. There is growing evidence that when a placebo leads to pain relief, it is because taking the placebo stimulates the production of endorphins.

It’s not just pain. In Parkinson’s disease, for example, a deficiency of a natural brain chemical makes it difficult for a person to move in a coordinated way. A pill that supplies that deficient chemical can improve the condition. One study showed that when people with Parkinson’s disease took a placebo pill (instead of the real pill), their brains responded by naturally making more of the missing chemical. That’s why they improved. It was not their imagination: It was natural healing that was stimulated by their belief in the pill.

Belief surely plays an important role. Studies show that people are more likely to respond to a placebo when they are told it is powerful or that it is expensive. People who believe in acupuncture are more likely to feel better following real acupuncture and during sham acupuncture. Studies like these have opened our eyes to what the placebo effect really is.