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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Minding Your Mind Minding Your Mind

Understanding the Placebo Response

September 24, 2013

By Michael Craig Miller M.D.

Harvard Medical School

Placebo. It's a term everyone has heard, but it is hard to understand. Even for medical professionals.

A placebo is a pill or other treatment that is inert (inactive). Researchers use them in clinical studies. They compare the results for a group of people who got an active treatment with the results for a group of people who got the placebo treatment. This is how researchers can tell how well a treatment worked.

But — comparisons aside — some studies show that a placebo itself can have dramatic effect on illness. And, the context in which a treatment takes place can bolster the placebo response.

So why would placebos work in some cases but not in others? This is a question that has puzzled researchers. To answer this, experts have been studying the nature of the placebo response itself.

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What's Behind the Placebo Response?

Many things contribute to the placebo response.

      • Brain biology — This is probably the best-known mechanism. The experience of taking inert pills is thought to activate endorphins in the brain. These can relieve pain.
      • Conditioning — In this learning process a person is repeatedly exposed to a neutral stimulus (such as a sugar pill). The stimulus is paired with an active intervention (such as an active drug). These two — the neutral placebo and the active treatment — become so linked in a person's brain that the very sight of the pill is sometimes enough to provide relief.
      • Expectation — Our expectations often affect the outcome or an experience. This is true when it comes to that shiny new gadget or medicines. When researchers describe a topical cream as a "powerful painkiller," participants report that it provides more pain relief than when the same cream is described as inert. When subjects are told that a pain reliever costs $2.50, more of them get relief than subjects who are told the same pill costs 10 cents.

Believers generally get better results than skeptics. Acupuncture believers have high expectations that the treatment will help them. These believers are roughly twice as likely to respond to acupuncture as are skeptics. The effect holds whether subjects receive a legitimate or sham variety of acupuncture. In clinical situations, these two processes may both be at work.

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Relationships Enhance the Placebo Effect

Consider three groups of patients with pain. One group is given real acupuncture. The second group gets fake (that is, placebo) acupuncture. The third group gets put on a waiting list. Patients in both the real and fake acupuncture groups get relief, while patients on the waiting list do not. That is, the placebo acupuncture works as well as the real acupuncture does.

Now consider research that looks at how the results are affected by the relationship with the clinician.

Let's divide the real and fake acupuncture groups again. For half of those patients, the treatment is provided in a businesslike manner. For the other half, the clinician is warm and understanding and gives the patient ample time. That is, the relationship is optimized.

The interaction with the clinician turns out to be more important than whether the patient gets real or placebo acupuncture. Whether the patient received the real thing or the pretend version of acupuncture, they get the same amount of relief. However, those patients who have empathetic interactions with clinicians do much better than those where the human contact is brief and businesslike.

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Context Counts

This research suggests that the therapeutic context and warm, positive clinician-patient interactions may enhance the placebo response. This may come as little surprise to mental health clinicians, who understand the value of building a therapeutic alliance with patients. But at a time when office visits are often reduced to 15-minute encounters, the acupuncture research provides a reminder that — although insurance companies may not want to reimburse for it — a caring encounter may be more likely than a rushed one to benefit the patient.

Michael Craig Miller, M.D. is the former editor-in-chief of the Harvard Mental Health Letter and an assistant professor of psychiatry at Harvard Medical School. Dr. Miller has an active clinical practice and has been on staff at Beth Israel Deaconess Medical Center for more than 30 years.

Finniss DG et al. "Placebo Effects: Biological, Clinical and Ethical Advances." The Lancet. 2010; 375(9715): 686–695.

Suarez-Almazor ME, Looney C, Liu Y, et al. "A randomized controlled trial of acupuncture for osteoarthritis of the knee: effects of patient-provider communication." Arthritis Care Research. Sep 2010; 62(9):1229-1236.

Cherkin DC, Sherman KJ, Avins AL, et al. "A randomized trial comparing acupuncture, simulated acupuncture, and usual care for chronic low back pain." Internal Medicine. 2009; 169(9):858-866.

Kaptchuk TJ, Kelley JM, Conboy LA, et al. "Components of placebo effect: randomised controlled trial in patients with irritable bowel syndrome." British Medical Journal. 2008; 336(7651):999-1003.

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