the placebo effect in an experimental study refers to the

• For educators
• English (US)
• English (India)
• English (UK)
• Greek Alphabet

This problem has been solved!

You'll get a detailed solution from a subject matter expert that helps you learn core concepts.

Question: The placebo effect in an experimental study refers to the: participants' expectations producing an outcome. effect of the third variable on the independent variable. difference between experimental and control groups. experimenter's expectation that the experimental group will perform better.

The interesting placebo effect occurs when a patient actually feels better after rece...

Not the question you’re looking for?

Post any question and get expert help quickly.

• Bipolar Disorder
• Therapy Center
• When To See a Therapist
• Types of Therapy
• Best Online Therapy
• Best Couples Therapy
• Managing Stress
• Sleep and Dreaming
• Understanding Emotions
• Self-Improvement
• Healthy Relationships
• Student Resources
• Personality Types
• Guided Meditations
• Verywell Mind Insights
• 2024 Verywell Mind 25
• Mental Health in the Classroom
• Editorial Process
• Meet Our Review Board
• Crisis Support

The Placebo Effect: Fake Treatment, Real Response

Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

solidcolours / Getty Images 

The mind can trick you into believing that a fake treatment has real therapeutic results, a phenomenon known as the placebo effect. In some cases, placebos can exert an influence powerful enough to mimic the effects of real medical treatments.

In this phenomenon, some people experience a benefit after the administration of an inactive lookalike substance or treatment. This substance, or placebo, has no known medical effect and can be in the form of a pill (sugar pill), injection (saline solution), or consumable liquid.

In most cases, the person does not know that the treatment they're receiving is actually a placebo. Instead, they believe they've received 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.

The placebo effect is much more than just positive thinking , however. When this occurs, many people have no idea they are responding to what is essentially a sugar pill. Placebos are often used in medical research to help doctors and scientists discover and understand the physiological and psychological effects of new medications.

Here's why the placebo effect is important, how it happens, and why it works.

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 of the Placebo Effect

Although researchers know that the placebo effect is real, they do not yet fully understand how and why it occurs. Various factors might contribute to this phenomenon.

Hormonal Response

One possible explanation is that taking the placebo triggers a release of endorphins. Endorphins have a structure similar to that of morphine and other opiate painkillers and act as the brain's own natural painkillers.

Researchers have demonstrated the placebo effect in action using brain scans, showing that areas with 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 condition
• Social : Reassuring body language, eye contact, and speech from a doctor or nurse
• Verbal : Listing to a health care provider talk positively about treatment

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.

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.

Placebo Effect Outcomes

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.

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

Weiner IB, Craighead WE.  The Corsini Encyclopedia of Psychology, Volume 3 . Hoboken, NJ: John Wiley & Sons. 2010.

By Kendra Cherry, MSEd Kendra Cherry, MS, is a psychosocial rehabilitation specialist, psychology educator, and author of the "Everything Psychology Book."

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Placebo effect.

Swapna Munnangi ; Joshua Henrina Sundjaja ; Karampal Singh ; Anterpreet Dua ; Lambros D. Angus .

Affiliations

Last Update: November 13, 2023 .

• Definition/Introduction

Placebos have been used in medicine since antiquity and may have been significant in improving health and quality of life when little was known about the etiology of most illnesses. Most outcomes were likely due to a placebo effect since the available treatments were unproven or have since been proven invalid. For example, snake oil and bloodletting was a common practice in the past; however, those who responded positively to those treatments likely did so because of a placebo effect. The emergence of placebo-controlled clinical trials in the 1940s reintroduced the placebo effect to the modern day. The classic article "The Powerful Placebo" by Henry Beecher highlighted the placebo effect and emphasized a need to account for it to evaluate the efficacy of a treatment modality properly. Both research and clinical settings utilize the placebo effect. [1] [2]

The placebo effect is a fascinating phenomenon that occurs when a sham medical intervention causes improvement in a patient's condition because of the factors associated with the patient's perception of the intervention. Examples of placebo interventions include sugar pills, saline injections, and therapeutic rituals. Placebo pills have even been commercially available in pharmacies in the past, although medical ethics prohibits their use now. [3] Placebo effects are not limited to inert interventions. Proven effective treatments can also generate a placebo effect. Traditionally, the placebo effect was considered a nuisance variable to be controlled for; however, in light of some remarkable research demonstrating its potential to modulate treatment outcomes in recent decades, there has been an increased interest in studying this phenomenon. [4]

The placebo effect can be verbally induced by conditioning and by prior experiences that shape patient expectations. Several research studies have demonstrated the placebo effect's role as a powerful determinant of health in certain disease conditions. Migraines, joint pain, arthritis, asthma, high blood pressure, and depression are some disease conditions that are more sensitive to the placebo effect. The placebo effect is a complex phenomenon with several underlying psychological and neurobiological mechanisms. These underlying mechanisms that mediate placebo responses differ based on the medical condition and the investigated outcomes. Not all results of a placebo are beneficial; as such, placebos can also result in undesirable outcomes. Indeed, the term "nocebo effect," derived from the Latin nocere meaning "harm," is commonly used when a placebo causes an unfavorable outcome. Both placebo and nocebo effects have the same mechanisms, presumably psychogenic, but they can induce measurable changes in the body. [5]

Mechanisms of Placebo Effect

Despite dramatic advances in scientific knowledge surrounding the placebo effect, efforts to characterize this phenomenon are in their primitive stages. The complex nature of mind-body interactions, supplemented by the negative connotations associated with placebo effects in the past, has hampered understanding of the phenomenon. However, researchers are beginning to unravel the neurobiological basis of placebo effects. Classical conditioning and expectancy are 2 hypothesized psychological mechanisms that mediate the placebo effect. Classical conditioning is a form of learning where an association is formed between a stimulus and a response. The association is then remembered, affecting future experiences. Through this process of association, patients may acquire a behavior. For example, a patient may report a decrease in pain after receiving a placebo pill that looks similar to pain medication that was previously effective in easing the pain. Whenever the same stimulus is encountered in the future, the patient conditions himself by shaping expectations and shows a previously imprinted response in his memory. Learning and adaptation, therefore, drive a conditioned response. [6]

Expectations of the patient also play a vital role in mediating a placebo effect. [7] Expectations can impact the course of treatment by affecting the psychological and physiological responses to that treatment. Along with classic conditioning, expectations can be induced by verbal instructions or social learning. For example, a research subject treated for pain with a placebo in the context of a verbal cue that the placebo is an effective analgesic may shape his expectations and elicit an analgesic response. Conditioning and expectancy are often entangled mechanisms mediating placebo responses. Neurobiological mechanisms underlying the placebo effect are best characterized in placebo analgesia.

In addition to these mechanisms, several other influential elements are at work during the placebo effect. These include the patient-physician relationship, the patient's psychological state and personality, the severity of the medical condition, and environmental circumstances. The patient's genetics may also influence the degree of the placebo effect. Researchers are studying how genes influence the placebo effect in various pathways, including dopamine, opioid, serotonin, and endocannabinoid systems. Evidence also indicates that the therapeutic benefits of the placebo effect may not impact the pathophysiology of the underlying disease being studied but rather address the subjective self-appraised symptoms of the disease. Elucidating the underlying mechanisms mediating the placebo effect may benefit clinical practice and drug development. [1]

• Issues of Concern

Placebo effects play a vital role in several areas. Placebo interventions primarily serve as control treatments in experimental studies, enabling researchers to determine the specific effects of a particular treatment. Clinical investigators use randomized, double-blind, placebo-controlled trials as a gold standard to validate treatments. [8] Non-blinded trials may result in a disproportionately large placebo effect. In placebo-controlled trials, the placebo effect observed may be more significant for psychological and self-rated measures relative to other more objective measures that are objective. Using a placebo in psychological and medical studies is advantageous as it helps minimize the influence of patient expectations on the outcome.

Additionally, studying the placebo effect at its core can help clinicians and researchers understand the context of how beliefs can shape various sensory and emotional perceptions. Identifying a physiological basis for the placebo effect may open doors to modulating processes that can improve mental and physical health. A clear understanding of the underlying mechanisms of placebo response with scientific work may enable clinicians to harness the placebo effect and enhance patient care.

It is challenging for medical professionals to sidestep the placebo effect and only measure the intrinsic activity of the tested treatment. Therefore, therapeutic evaluations become difficult in medical conditions sensitive to the placebo effect. Interindividual differences also complicate the studies of the placebo effect. Physicians must separate the placebo effect from the treatment. Placebo research is challenging because of a certain degree of deception.

• Clinical Significance

Understanding how the placebo responses form is vital for clinical practice and can be crucial in determining the patient's therapeutic outcome. Although placebo effects frequently occur in clinical practice, they often go under-recognized. The therapeutic rituals and the psychosocial context surrounding the patient can mediate a placebo effect. The placebo effect is considered a melting pot of ideas in neuroscience. Translating the knowledge of the placebo effect to benefit the patient requires a thorough evaluation of the clinical effectiveness of the intended effect. Therefore, attempts to generate beneficial placebo responses should be made only under strict professional, legal, and ethical norms after obtaining appropriate informed consent. [9]

Placebo effects have also been a subject of ethical concern in clinical practice. Additionally, the ethical dimensions of placebo-controlled trials, such as using sham invasive procedures, withholding potential proven treatments, or deception, are issues of concern in studying the placebo effect. [10]

• Nursing, Allied Health, and Interprofessional Team Interventions

An understanding of the placebo effect and a coordinated team effort must be made by prescribers, nursing staff, and pharmacists to ethically treat patients, particularly during the design and performance of placebo-controlled trials.

• Review Questions
• Access free multiple choice questions on this topic.
• Comment on this article.

Disclosure: Swapna Munnangi declares no relevant financial relationships with ineligible companies.

Disclosure: Joshua Henrina Sundjaja declares no relevant financial relationships with ineligible companies.

Disclosure: Karampal Singh declares no relevant financial relationships with ineligible companies.

Disclosure: Anterpreet Dua declares no relevant financial relationships with ineligible companies.

Disclosure: Lambros Angus declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

• Cite this Page Munnangi S, Sundjaja JH, Singh K, et al. Placebo Effect. [Updated 2023 Nov 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

In this Page

Bulk download.

• Bulk download StatPearls data from FTP

Related information

• PMC PubMed Central citations
• PubMed Links to PubMed

Similar articles in PubMed

• The powerful placebo effect: fact or fiction? [J Clin Epidemiol. 1997] The powerful placebo effect: fact or fiction? Kienle GS, Kiene H. J Clin Epidemiol. 1997 Dec; 50(12):1311-8.
• Review Better than nothing: A historical account of placebos and placebo effects from modern to contemporary medicine. [Int Rev Neurobiol. 2020] Review Better than nothing: A historical account of placebos and placebo effects from modern to contemporary medicine. Annoni M. Int Rev Neurobiol. 2020; 153:3-26. Epub 2020 Jun 9.
• Homage to Henry Beecher (1904-1976). [Perspect Biol Med. 2012] Homage to Henry Beecher (1904-1976). Miller FG. Perspect Biol Med. 2012; 55(2):218-29.
• Review Ivermectin for preventing and treating COVID-19. [Cochrane Database Syst Rev. 2022] Review Ivermectin for preventing and treating COVID-19. Popp M, Reis S, Schießer S, Hausinger RI, Stegemann M, Metzendorf MI, Kranke P, Meybohm P, Skoetz N, Weibel S. Cochrane Database Syst Rev. 2022 Jun 21; 6(6):CD015017. Epub 2022 Jun 21.
• Review Placebo effect and placebo concept: a critical methodological and conceptual analysis of reports on the magnitude of the placebo effect. [Altern Ther Health Med. 1996] Review Placebo effect and placebo concept: a critical methodological and conceptual analysis of reports on the magnitude of the placebo effect. Kienle GS, Kiene H. Altern Ther Health Med. 1996 Nov; 2(6):39-54.

Recent Activity

• Placebo Effect - StatPearls Placebo Effect - StatPearls

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

• Science Notes Posts
• Contact Science Notes
• Todd Helmenstine Biography
• Anne Helmenstine Biography
• Free Printable Periodic Tables (PDF and PNG)
• Periodic Table Wallpapers
• Interactive Periodic Table
• Periodic Table Posters
• Science Experiments for Kids
• How to Grow Crystals
• Chemistry Projects
• Fire and Flames Projects
• Holiday Science
• Chemistry Problems With Answers
• Physics Problems
• Unit Conversion Example Problems
• Chemistry Worksheets
• Biology Worksheets
• Periodic Table Worksheets
• Physical Science Worksheets
• Science Lab Worksheets
• My Amazon Books

Placebo Effect – What It Is and How It Works

The placebo effect is the phenomenon where a subject experiences an effect from an inactive substance or fake treatment, which is called a placebo . While not all people experience the placebo effect (certainly not in all situations), there are genuine therapeutic effects of placebos. Here is a look at what the placebo effect is, why it occurs, and how scientists and health professionals use it.

• A placebo is a fake treatment, which can have genuine therapeutic value, called the placebo effect.
• Examples of placebos include sugar pills and saline solution injections.
• The placebo effect helps providing relief from depression, pain, and certain other conditions.
• Overall, the placebo effect occurs because any treatment (real or a placebo) affects the brain, which responds to the stimulus and produces a physiological effect.

Placebo vs Placebo Effect

The placebo effect is a therapeutic benefit or apparent side effect from a placebo. A placebo, in turn, is a substance or treatment that has no effect. Alternatively, it is a treatment with the exact composition of inactive ingredients or the same steps as the therapy, minus the active substance or procedure.

Examples of placebos include sugar pills, consumable liquids or solids, saline injections, and fake surgeries.

The Nocebo Effect

Sometimes the placebo effect refers to any response to a fake treatment. However, other scientists refer to a therapeutic or beneficial response as the placebo effect and side effects or a negative response as the nocebo effect (negative placebo). The nocebo effect also includes withdrawal symptoms some patients experience after discontinuing a placebo treatment.

Uses of Placebos

The primary use of a placebo is in scientific research and drug testing. A researcher administers the placebo to a control group , while the experimental group receives the treatment. Assuming the placebo is identical to the treatment in every respect except the active ingredient or treatment, this type of experiment identifies the efficacy of the treatment with a high degree of confidence. Also, using a placebo makes double blind experiments possible.

However, when you compare the outcomes for an experimental group, placebo group, and a control group that receives no treatment whatsoever, then the placebo effect becomes apparent. This type of study also reveals “inactive ingredients” that aren’t actually inactive. The placebo effect does not influence the outcomes of all studies, but it is a major factor in others.

Situations Where Placebos Work

So, knowing that the placebo effect is a real phenomenon, scientists and medical professionals studied the effectiveness of placebos. In some situations, a placebo is an effective treatment, even when people know they are taking a placebo. Placebos have an effect on:

• Irritable bowel syndrome
• Sleep disorders

Studies indicate some people taking a placebo for a stimulant experience increased heart rate and blood pressure, while those taking a placebo for a depressant experience the opposite effects.

How the Placebo Effect Works

There is no single definitive mechanism for how the placebo effect works. Multiple factors likely play a role:

• Expectation : Basically, what we believe we will experience from a treatment plays a part in the actual effect. So, if you think an injection will hurt, it probably will. Or, if you think a pill (real or placebo) helps a condition, then it likely does. Even if you know a treatment is a placebo, receiving care from a health professional aids in a positive response.
• Conditioning : Conditioning is a learned response or association between two events. For example, in one study, rats drank a saccharin-sweetened beverage containing the immunosuppressant cyclophosphamide. After three days of conditioning, rats given the saccharin beverage minus the cyclophosphamide still displayed suppressed immune responses.
• Genetics : Some subjects are genetically predisposed to respond to placebos. For example, in one study, people carrying a gene coding for higher levels of the neurotransmitter dopamine were more likely to experience the placebo effect than those with a gene for lower dopamine production.

Studies indicate that the brain controls a variety of responses that manifest as the placebo effect. Physiological processes subject to placebos include pain response, depression, insulin secretion, immunosuppression, symptoms of Parkinson’s disease, and serum iron levels. Brain imaging shows a placebo for pain relief activates several regions of the nervous system, including the spinal cord, amygdala, nucleus accumbens, and anterior cingulate, insular, orbitofrontal, and prefrontal cortices in the brain.

• Ader, R.; Cohen, N. (1975). “Behaviorally conditioned immunosuppression”. Psychosomatic Medicine . 37 (4): 333–40. doi: 10.1097/00006842-197507000-00007
• Eippert, F.; Bingel, U.; Schoell, E.D.; et al. (2009). “Activation of the opioidergic descending pain control system underlies placebo analgesia”. Neuron . 63 (4):533-543. doi: 10.1016/j.neuron.2009.07.014
• Gross, Liza (2017). “Putting placebos to the test”. PLOS Biology . 15 (2): e2001998. doi: 10.1371/journal.pbio.2001998
• Häuser, W.; Hansen, E.; Enck, P. (June). “Nocebo phenomena in medicine: their relevance in everyday clinical practice”. Deutsches Ärzteblatt International . 109 (26): 459–65. doi: 10.3238/arztebl.2012.0459
• Khan, A.; Redding, N.; Brown, W.A. (2008). “The persistence of the placebo response in antidepressant clinical trials”. Journal of Psychiatric Research . 42 (10): 791–6. doi: 10.1016/j.jpsychires.2007.10.004
• Price, D.D.; Finniss, D.G.; Benedetti, F. (2008). “A comprehensive review of the placebo effect: recent advances and current thought”. Annual Review of Psychology . 59 (1): 565–90. doi: 10.1146/annurev.psych.59.113006.095941

Related Posts