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Placebo Effect: Definition & Explanation

Instructor: Lisa Roundy

Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.

The placebo effect occurs when a person believes that he or she is receiving real treatment and reports an improvement in his or her condition. In this lesson, learn what may cause the placebo effect and its importance in research.

Definition of the Placebo Effect

Imagine you have volunteered for a study that determines the effectiveness of a new headache drug. You take the pill you have been given, believing that it will help your headache. You find that your headache feels much better after taking the pill. Later, you are told that you did not actually receive the new medicine in the study at all but were given a placebo instead. A placebo is something given to a person that has no real physical effect.

If you were not given the medication, why did your headache feel better after you took the pill you were given? The answer to this question is that you experienced the placebo effect. The placebo effect is a phenomenon that occurs when a person believes he or she is receiving real treatment and reports an improvement in his or her condition.

What Causes the Placebo Effect?

You now know that your headache improved due to the placebo effect, but you are still wondering why? This is a question that researchers have been asking for a long time as well. It is still not fully understood exactly what causes the placebo effect, but there have been some interesting findings. Let's use the example of your headache and apply it to theories about why the placebo effect takes place.

One theory is that you had high expectations that the pill would work, and therefore it did. This is a mind-over-matter situation in which you believed so strongly in something that it happened. You had the belief that the pill you were given would help your headache. You have been taught to believe that medicine makes you feel better when you take it. Since you expected the pill to work, it did. This means you had a conditioned response to taking the pill. A conditioned response occurs when you have a recurring response to a particular stimulus. In this case, the stimulus was taking medicine and your response was feeling better.

Another theory is that your brain may have tricked you into believing the pill was working. In brain scans, researchers have found that some people given a placebo will produce similar brain activity to a person given real treatment.

The last common theory is that the combination of your doctor's reassurance and your faith in the treatment lead to a decrease in your stress level. Stress and anxiety adversely affect the body and can increase your focus on symptoms. Reducing this stress may have reduced your physical symptoms.

The Importance of the Placebo Effect in Research

In the previous example, you were given the placebo in a research study of a new medication. Why did the researchers give you a placebo instead of the real medication?

The purpose of doing this is to determine whether or not the treatment has an actual effect. The placebo effect is a real and powerful psychological response. It tends to be thought of as a response to an inert treatment, but it is actually present in all treatments. For this reason, the study gives one group the placebo.

Placebos are often used in blind trials such as this. A blind trial is a type of experiment in which the participants are not aware of which group they are assigned to. One group is given the medicine or treatment being tested. The other group is given a placebo. Only the researchers know who gets the real treatment and who gets the placebo. In other words, the participants are 'blind' to their situation.

They are also used in double blind trials. A double blind trial is similar to a blind trial, but neither the researcher or the participant know who is assigned to which group. This eliminates the occurrence of any bias due to the researcher's perceptions.

Imagine you are examining the results of a blind trial. The study is trying to find out if a new medication improves the symptoms of depression. Group 1 is given the new medication, and group 2 is given a placebo. In this case, group 2 is the control group. A control group is the group in a study that does not receive treatment and is used as a benchmark to measure the results of the other group. A control group can be a placebo group or a third group that receives neither the placebo nor the medication.

You notice that two-thirds of the people in group 1 report feeling less depressed after taking the medication. You also notice that one-third of the people in group 2 report feeling less depressed after taking the placebo.

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