Basics What Is the Placebo Effect? By Kendra Cherry Kendra Cherry Facebook Twitter Kendra Cherry, MS, is an author and educational consultant focused on helping students learn about psychology. Learn about our editorial process Updated on April 25, 2021 Medically reviewed Verywell Mind articles are reviewed by board-certified physicians and mental healthcare professionals. Medical Reviewers confirm the content is thorough and accurate, reflecting the latest evidence-based research. Content is reviewed before publication and upon substantial updates. Learn more. by David Susman, PhD Medically reviewed by David Susman, PhD David Susman, PhD is a licensed clinical psychologist with experience providing treatment to individuals with mental illness and substance use concerns. Learn about our Medical Review Board Print solidcolours / Getty Images Table of Contents View All Table of Contents What Is the Placebo Effect? Causes Examples Benefits of Using a Placebo Effect The mind can have a powerful influence on the body, and in some cases, can even help the body heal. The mind can even sometimes trick you into believing that a fake treatment has real therapeutic results, a phenomenon that is known as the placebo effect. In some cases, placebos can exert an influence powerful enough to mimic the effects of real medical treatments. But the placebo effect is much more than just positive thinking. When this response occurs, many people have no idea they are responding to what is essentially a "sugar pill." Placebos are often utilized in medical research to help doctors and scientists discover and better understand the physiological and psychological effects of new medications. In order to understand why the placebo effect is important, it is essential to understand a bit more about how and why it works. What Is the Placebo Effect? The placebo effect is defined as a phenomenon in which some people experience a benefit after the administration of an inactive "look-alike" substance or treatment. This substance, or placebo, has no known medical effect. Sometimes the placebo is in the form of a pill (sugar pill), but it can also be an injection (saline solution) or consumable liquid. In most cases, the person does not know that the treatment they are receiving is actually a placebo. Instead, they believe that they are the recipient of the real treatment. The placebo is designed to seem exactly like the real treatment, yet the substance has no actual effect on the condition it purports to treat. Placebo vs. Placebo Effect It is important to note that a "placebo" and the "placebo effect" are different things. The term placebo refers to the inactive substance itself, while the term placebo effect refers to any effects of taking a medicine that cannot be attributed to the treatment itself. Causes Why do people experience real changes as a result of fake treatments? While researchers know that the placebo effect is a real effect, they do not yet fully understand how and why this effect occurs. Research is ongoing as to why some people experience changes even when they are only receiving a placebo. A number of different factors may contribute to this phenomenon. Hormone Response One possible explanation is that taking the placebo triggered a release of endorphins. Endorphins have a structure similar to morphine and other opiate painkillers and act as the brain's own natural painkillers. Researchers have been able to demonstrate the placebo effect in action using brain scans, showing that areas that contain many opiate receptors were activated in both the placebo and treatment groups. Naloxone is an opioid antagonist that blocks both natural endorphins and opioid drugs. After people received naloxone, placebo pain relief was reduced. Conditioning Other possible explanations include classical conditioning, or when you form an association between two stimuli resulting in a learned response. In some cases, a placebo can be paired with an actual treatment until it evokes the desired effect. For example, if you're regularly given the same arthritis pill to relieve stiff, sore joints, you may begin to associate that pill with pain relief. If you're given a placebo that looks similar to your arthritis pill, you may still believe it provides pain relief because you've been conditioned to do so. Expectation Expectations, or what we believe we will experience, have been found to play a significant role in the placebo effect. People who are highly motivated and expect the treatment to work may be more likely to experience a placebo effect. A prescribing physician's enthusiasm for treatment can even impact how a patient responds. If a doctor seems very positive that a treatment will have a desirable effect, a patient may be more likely to see benefits from taking the drug. This demonstrates that the placebo effect can even take place when a patient is taking real medications to treat an illness. Verbal, behavioral, and social cues can contribute to a person's expectations of whether the medication will have an effect. Behavioral: The act of taking a pill or receiving an injection to improve your conditionSocial: Reassuring body language, eye contact, and speech from a doctor or nurseVerbal: Listing to a health care provider talk positively about treatment Genetics Genes may also influence how people respond to placebo treatments. Some people are genetically predisposed to respond more to placebos. One study found that people with a gene variant that codes for higher levels of the brain chemical dopamine are more prone to the placebo effect than those with the low-dopamine version. People with the high-dopamine version of this gene also tend to have higher levels of pain perception and reward-seeking. The Nocebo Effect Conversely, individuals can experience more symptoms or side effects as a response to a placebo, a response that is sometimes referred to as the "nocebo effect." For example, a patient might report having headaches, nausea, or dizziness in response to a placebo. Examples The placebo effect can be used in a variety of ways, including in medical research and psychology research to learn more about the physiological and psychological effects of new medications. In Medical Research In medical research, some people in a study may be given a placebo, while others get the new treatment being tested. The purpose of doing this is to determine the effectiveness of the new treatment. If participants taking the actual drug demonstrate a significant improvement over those taking the placebo, the study can help support the claim for the drug's effectiveness. When testing new medications or therapies, scientists want to know if the new treatment works and if it's better than what's already available. Through their research, they learn the sort of side effects the new treatment might produce, which patients may benefit the most, and if the potential benefits outweigh the risks. By comparing the effects of a treatment to a placebo, researchers hope to be able to determine if the effects of the medicine are due to the treatment itself or caused by some other variable. In Psychology Experiments In a psychology experiment, a placebo is an inert treatment or substance that has no known effects. Researchers might utilize a placebo control group, which is a group of participants who are exposed to the placebo or fake independent variable. The impact of this placebo treatment is then compared to the results of the experimental group. Even though placebos contain no real treatment, researchers have found they can have a variety of both physical and psychological effects. Participants in placebo groups have displayed changes in heart rate, blood pressure, anxiety levels, pain perception, fatigue, and even brain activity. These effects point to the brain's role in health and well-being. Benefits of Using a Placebo The major advantage of using a placebo when evaluating a new drug is that it weakens or eliminates the effect that expectations can have on the outcome. If researchers expect a certain result, they may unknowingly give clues to participants about how they should behave. This can affect the results of the study. To minimize this, researchers sometimes conduct what is known as a double-blind study. In this type of study, neither the study participants nor the researchers know who is getting the placebo and who is getting the real treatment. By minimizing the risk of these subtle biases influencing the study, researchers are better able to look at the effects of the drug and the placebo. One of the most studied and strongest placebo effects is in the reduction of pain. According to some estimates, approximately 30% to 60% of people will feel that their pain has diminished after taking a placebo pill. For example, imagine that a participant has volunteered for a study to determine the effectiveness of a new headache drug. After taking the drug, she finds that her headache quickly dissipates, and she feels much better. However, she later learns that she was in the placebo group and that the drug she was given was just a sugar pill. Effect While placebos can affect how a person feels, studies suggest that they do not have a significant impact on underlying illnesses. A major review of more than 150 clinical trials involving placebos found that placebos had no major clinical effects on illnesses. Instead, the placebo effect had a small influence on patient-reported outcomes, particularly of perceptions of nausea and pain. However, another review conducted nearly 10 years later found that in similar populations, both placebos and treatments had similar effects. The authors concluded that placebos, when used appropriately, could potentially benefit patients as part of a therapeutic plan. Depression: The placebo effect has been found to impact people with major depression disorder. In one study, participants who weren’t currently taking any other medication were given placebo pills labeled as either fast-acting antidepressants or placebo for one week. After the week, the researchers took PET scans and told the participants they were receiving an injection to improve mood. Participants who took the placebo labeled as an antidepressant as well as the injection reported decreased depression symptoms and increased brain activity in areas of the brain linked to emotion and stress regulation.Pain management: A small 2014 study tested the placebo effect on 66 people with episodic migraine, who were asked to take an assigned pill—either a placebo or Maxalt (rizatriptan), which is a known migraine medication—and rate their pain intensity. Some people were told the pill was a placebo, some were told it was Maxalt, and others were told it could be either. Researchers found that the expectations set by the pill labeling influenced the participants responses. Even when Maxalt was labeled as a placebo, participants gave it the same rating as a placebo that was labeled Maxalt.Symptom relief: The placebo effect has also been studied on cancer survivors who experience cancer-related fatigue. Participants received three weeks of treatment, either their regular treatment or a pill labeled as a placebo. The study found that the placebo (despite being labeled as such) was reported to improve symptoms while taking the medication and three weeks after discontinuation. A Word From Verywell The placebo effect can have a powerful influence on how people feel, but it is important to remember that they are not a cure for an underlying condition. Healthcare providers aren't allowed to use placebos in actual practice without informing patients (this would be considered unethical care), which reduces or eliminates the desired placebo effect. However, by using placebos in research, during which they don't have to inform the participant, scientists are able to get a better idea of how treatments impact patients and whether new medications and treatment approaches are safe and effective. 10 Sources Verywell Mind uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Eippert F, Bingel U, Schoell ED, et al. Activation of the opioidergic descending pain control system underlies placebo analgesia. Neuron. 2009;63(4):533-543. doi:10.1016/j.neuron.2009.07.014 Bąbel P. Classical conditioning as a distinct mechanism of placebo effects. Front Psychiatry. 2019;10:449. doi:10.3389/fpsyt.2019.00449 Brown WA. Expectation, the placebo effect and the response to treatment. R I Med J (2013). 2015;98(5):19-21. Hall KT, Lembo AJ, Kirsch I, et al. Catechol-O-methyltransferase val158met polymorphism predicts placebo effect in irritable bowel syndrome. PLoS One. 2012;7(10):e48135. doi:10.1371/journal.pone.0048135 Colloca L. The placebo effect in pain therapies. Annu Rev Pharmacol Toxicol. 2019;59:191-211. doi:10.1146/annurev-pharmtox-010818-021542 Hróbjartsson A, Gøtzsche PC. Placebo interventions for all clinical conditions. Cochrane Database Syst Rev. 2004;(3):CD003974. doi:10.1002/14651858.CD003974.pub2 Howick J, Friedemann C, Tsakok M, et al. Are treatments more effective than placebos? A systematic review and meta-analysis. PLoS One. 2013;8(5):e62599. doi:10.1371/journal.pone.0062599 Peciña M, Bohnert ASB, Sikora M, et al. Association between placebo-activated neural systems and antidepressant responses: Neurochemistry of placebo effects in major depression. JAMA Psychiatry. 2015;72(11):1087. doi:10.1001/jamapsychiatry.2015.1335 Kam-Hansen S, Jakubowski M, Kelley JM, et al. Altered placebo and drug labeling changes the outcome of episodic migraine attacks. Science Translational Medicine. 2014;6(218):218ra5-218ra5. doi:10.1126/scitranslmed.3006175 Hoenemeyer TW, Kaptchuk TJ, Mehta TS, Fontaine KR. Open-label placebo treatment for cancer-related fatigue: A randomized-controlled clinical trial. Sci Rep. 2018;8(1):2784. doi:10.1038/s41598-018-20993-y Additional Reading Weiner IB, Craighead WE. The Corsini Encyclopedia of Psychology, Volume 3. Hoboken, NJ: John Wiley & Sons. 2010. Editorial Process Our Review Board Share Feedback Was this page helpful? Thanks for your feedback! What is your feedback? Other Helpful Report an Error Submit Speak to a Therapist Online Advertiser Disclosure × The offers that appear in this table are from partnerships from which Verywell Mind receives compensation.