Placebo effect eases pain — even if participants are aware
Effects are “independent of reported expectations for pain relief”
The placebo effect eases pain even if research participants know the treatment they are receiving has no medical value whatsoever, according to a recent study. Some ethical considerations of treatment include the following:
- Reinforcing treatment cues with positive outcomes can create placebo effects that are independent of reported expectations for pain relief.
- The placebo effect could not be achieved without the initial conditioning effect, which required nondisclosure of placebo use.
- The use of deception or non-disclosure may be necessary in clinical trials.
In some cases, the placebo effect still works even if research participants know the treatment they are receiving to ease pain has no medical value whatsoever, according to a recent study.1
Researchers applied a heating element to research subjects’ forearms to induce pain sensations, though not enough to burn the skin. They then applied what the subject thought was an analgesic gel and turned down the temperature.
The participants were divided into two groups — those who received four “conditioning” sessions or only one session. After the researchers revealed the treatment was fake, only the group who received four sessions continued to get pain relief from the placebo.
“These findings suggest that reinforcing treatment cues with positive outcomes can create placebo effects that are independent of reported expectations for pain relief,” says the study’s lead author, University of Colorado Boulder graduate student Scott Schafer.
The effectiveness of a placebo in providing pain relief is often related to a subject’s expectations for pain relief. “While conditioning procedures that pair a placebo with pain relief enhance the subsequent placebo response, they also strengthen expectations for pain relief,” notes Schafer.
Conditioning effects on pain are largely thought to be linked to changes in expectations. “By that theory, removing expectations should have eliminated the placebo response,” says Schafer. “So, in that sense, these results were quite surprising.”
Ben A. Rich, JD, PhD, emeritus professor of medicine (Bioethics) at University of California, Davis School of Medicine, participated in the development of ethical guidelines addressing the use of placebos in pain medicine.
The deceptive use of placebos and the misinterpretation of the placebo response to discredit the patient’s pain report are unethical and should be avoided, according to the American Pain Society’s 2005 position statement.2 In its 2007 Ethics Charter, the American Academy of Pain Medicine states that placebo use for the treatment of pain in other than research settings is usually considered unjustifiable, both for ethical and clinical reasons.3
In light of these two guidelines, says Rich, “the burden of persuasion that the benefits of the deceptive use of placebos outweigh the risks falls on those who would keep patients or research subjects uninformed — either for their own good, or in the cause of the advancement of medical science.”
Rich notes that in the 2015 study, the placebo effect could not be achieved without the initial conditioning effect. This required nondisclosure of placebo use. “There is a potential adverse effect on the trust relationship between clinician and patient or clinical investigator and research subject,” says Rich.
The research subjects were surprised with the knowledge that their previous treatments were a placebo. “A fully ethical implementation of the same procedure in clinical practice, such as pain management post-surgery, would necessitate a disclosure of future placebo administration,” says Schafer.
However, says Schafer, the exact timing of the shift from a verum drug treatment to a placebo could be hidden in order to preserve the conditioning effect. “This could replicate our effect and maintain the effectiveness of a placebo, even after subjects are sure that the treatment has shifted to a placebo,” he says.
Use of placebos in human subjects research is generally ethically acceptable when subjects are informed in advance that they may receive a placebo and they nevertheless consent to participate, says Rich. “The deception or deliberate nondisclosure of otherwise pertinent information, whether or not it involves the use of placebos, is likely to undermine trust in either the patient care or clinical research enterprise,” he says.
Studying the placebo effect is an important part of medical science, and involves many complex, ambiguous factors, says Joyce Plaza, MS, MBe, manager of New York City-based Columbia University’s IRB. “The use of deception or non-disclosure may be necessary,” she adds. Plaza says the use of placebos in research is ethical if one of the following two conditions exists:
- For studies involving minimal risk, the use of deception is permissible if the study could not be otherwise conducted, the study presents minimal risk, the rights and welfare of the subjects are not adversely affected, and subjects are fully debriefed after their participation, or at the conclusion of the study, if appropriate.
- Placebos may be used in double-blinded clinical studies in which subjects are informed that they may receive the placebo instead of the experimental active treatment, but subjects are also provided standard care in addition to the placebo or active treatment. “The review of the studies by the institutional review board would determine that the ethical responsibilities of the research were met,” says Plaza.
In an earlier study, openly administered placebos were found to be as effective as lidocaine at treating pain from irritable bowel syndrome.4 “Critically, in this case subjects were informed about the effectiveness of placebos in treating pain, and were implicitly encouraged to expect the placebos to work,” notes Schafer.
In the 2015 study, participants were permitted to stop their participation if they experienced discomfort from the heat, and gave informed consent to participate in a study of treatment effects on pain relief. “All participants were fully debriefed at the conclusion of the study,” notes Plaza.
- Schafer SM Colloca L, Wager TD. Conditioned placebo analgesia persists when subjects know they are receiving a placebo. J Pain 2015; 16(5):412-420.
- AAPM Council on Ethics. Ethics charter from American Academy of Pain Medicine. Pain Med 2005; 6(3):203-212.
- American Pain Society Ethics Committee. APS position statement on the use of placebos in pain management. J Pain 2005; 6(4):215-217.
- Kaptchuk TJ, Friedlander E, Kelley JM, et al. Placebos without deception: A randomized controlled trial in irritable bowel syndrome. PloS One 2010; 5(12):e15591.
- Joyce Plaza, MS, MBe, Institutional Review Board, Columbia University, New York City. Phone: (212) 851-7041. Email: [email protected].
- Ben A. Rich, JD, PhD, Emeritus Professor of Medicine (Bioethics), UC Davis School of Medicine. Phone: (916) 734-6010. Fax: (916) 734-1531. Email: [email protected].
- Scott Schafer, University of Colorado Boulder. Email: [email protected].
The placebo effect eases pain even if research participants know the treatment they are receiving has no medical value whatsoever, according to a recent study.
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