Placebo Effect

Two sugar pillsThe placebo effect occurs when a person reports an improvement in symptoms after taking a medication that contains no ingredients that should cause symptom improvement. The effect requires that a person believes that the medication will work. For example, a person with depression who is given a sugar pill and is told that the medication is an antidepressant may report an improvement in their depression. A related effect, the nocebo effect, occurs when a person believes a substance will harm them and then reports negative symptoms.

Experiments Involving Placebos

In experiments testing medications, subjects are frequently divided into three groups:

  1. One group receives no treatment
  2. The second group receives the medication being tested
  3. The third group receives a placebo such as a sugar pill

Experimenters typically compare the results of the placebo group to the medication group to determine how much improvement is attributable to the medication versus simply to a belief that the medication will work. Many drugs turn out to be only slightly more effective than placebos.


The placebo effect is directly related to a person’s expectations. The more strongly a person believes in a medication’s efficacy, the more significant the effect of the medication is likely to be. Brain imaging tests indicate that the use of a placebo may activate portions of the brain related to information processing. Thus, people who take placebos may view their symptoms differently or may become more motivated to feel better.


  1. American Psychological Association. APA concise dictionary of psychology. Washington, DC. American Psychological Association, 2009. Print.
  2. Kring, A. M., Johnson, S. L., Davison, G. C., & Neale, J. M. (2010). Abnormal psychology. Hoboken, NJ: John Wiley & Sons.
  3. Placebo Effect. (n.d.).  Scientific american. Retrieved from

Last Updated: 08-17-2015

Leave a Comment

By commenting you acknowledge acceptance of's Terms and Conditions of Use.

* Indicates required field.

Therapist   Treatment Center

Advanced Search is not intended to be a substitute for professional advice, diagnosis, medical treatment, or therapy. Always seek the advice of your physician or qualified mental health provider with any questions you may have regarding any mental health symptom or medical condition. Never disregard professional psychological or medical advice nor delay in seeking professional advice or treatment because of something you have read on