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Telling people they’re getting a placebo does not stop it from working

After being given a placebo and viewing negative images, people felt less distress, even though they knew their treatment had no active ingredients.

Image Credit: Free Images

Can a pill with no medicinal ingredients cure physical diseases or relieve pain? Research is still ongoing, but one study found that it may have a positive impact on emotional distress.

Treatments that produce positive effects without active ingredients are known as “placebos.” There are two kinds of placebos: one where the person thinks they are receiving medicine, and one where the person knows they are receiving a placebo. The authors of this study focused on the second type and used the term “non-deceptive placebo” to describe it. Both types of placebo have been shown to work on certain conditions because they rely on the same principle – the person taking the placebo just has to believe it will improve their condition.

The ethics of placebos have been questioned, because it requires the doctor to trick the patient by saying they are giving them medicine when actually, the treatment has no active ingredients. But does the doctor have to deceive the patient for the placebo to work? The mechanisms of placebos are not well-understood. Do the placebos cause objective physical effects that can be measured, or do they just make people perceive that they are feeling better? And do those effects depend on the patient believing it is really medicine?

Researchers from Michigan State University and the University of Michigan designed an experiment to test whether knowing a treatment was a placebo would affect the results and to detect physical differences in the placebo group. The first step in their work was determining what conditions placebos were effective on and what previous experiments had been done with non-deceptive placebos.

Of the 26 studies they found, most reported positive effects, but they were all self-reported. Only 8 studies measured objective markers. Only one found an improvement, and it was in performing a task. However, most of the studies measured physical conditions that deceptive placebos do not improve, such as wound healing. So, these researchers decided to measure the impact of non-deceptive placebos on a condition that deceptive placebos have been shown to help with – emotional distress.

The researchers conducted two experiments, using healthy men and women between ages 18 and 30 recruited from two universities. The first experiment was to determine how people said they felt. The second would measure distress more objectively – using brain activity.

Before the experiment, the control group was given an article to read about treating pain, and given a nasal spray they were told would make measurements more accurate. The non-deceptive placebo group read an article about placebos and how they work, including that they work even if the person knows it is a placebo. They were given the same nasal spray, but were told it had no active ingredients.

In the first experiment, everyone was shown 40 images, 30 of which were negative and 10 of which were neutral. The image was shown for a few seconds, then the viewers were asked how they felt on a scale of 1-9. The people who knew the spray was a placebo reported feeling less negative on average after viewing distressing images.

The second experiment determined whether the participants’ feelings were physically reflected in brain activity. The researchers showed negative and neutral images in a random order for a few seconds with a screen in between asking them to clear their mind. While they did this, they scanned the brains of the participants and measured the response at two time points. The first time point was the brain’s immediate reaction to the image. The second time point indicated when the person had emotionally processed and understood the image.

They found no differences in brain activity levels between the two groups during the first period after negative images, implying that the placebo did not affect the initial reaction. But the placebo group showed less activity during the second period, meaning they were able to process and regulate their distress more effectively. They noted that a similar pattern has been observed in placebo studies on pain perception.

The researchers in this study tried to identify and correct for confounding variables. They asked participants about their opinion on placebos. It turns out, people who did not believe strongly in placebos still experienced the same effects. To avoid interference from biological differences in brain activity, they only recruited women to participate in the second experiment. But would the same effect be seen in men? That is not known.

While placebos still cannot not fix a broken arm, the authors conclude that these results could lead to new directions for treatment plans for emotional regulation disorders, depression, and the emotional distress that comes with chronic pain.

Study Information

Original study: Placebos without deception reduce self-report and neural measures of emotional distress

Study was published on: July 29, 2020

Study author(s): Darwin A. Guevarra, Jason S. Moser, Tor D. Wager & Ethan Kross

The study was done at: University of Michigan, Michigan State University, University of Colorado, Dartmouth College (USA)

The study was funded by: Funding came from authors' Ethan Kross and Jason Moser's research funds (not affiliated with a grant)

Raw data availability:

Featured image credit: Free Images

This summary was edited by: Gina Misra