Study: Placebos Effective Even When People Know They’re Taking Them

A team of researchers that includes scientists from Michigan State University in East Lansing and the University of Michigan in Ann Arbor have found that placebos aid in treatment, even when people know they are taking them.
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MSU and U-M researchers have found that placebos aid in treatment, even when people know they are taking placebos instead of medicine with active ingredients. // Photo courtesy of Michigan State University

A team of researchers that includes scientists from Michigan State University in East Lansing and the University of Michigan in Ann Arbor have found that placebos aid in treatment, even when people know they are taking them.

The placebo effect, in which people often feel better after taking a sugar pill without active ingredients simply because they believe it’s real, is well documented. The team, which also includes researchers from Dartmouth College in New Hampshire, is the first to demonstrate that placebos reduce brain markers of emotional distress even when people know they are taking a placebo instead of an actual medication.

The evidence shows that even if people are aware that their treatment does not contain active ingredients – or are what is called nondeceptive placebos – believing that the treatment can heal can lead to changes in how the brain reacts to emotional information.

“Just think: What if someone took a side effect-free sugar pill twice a day after going through a short convincing video on the power of placebos and experienced reduced stress as a result?” says Darwin Guevarra, postdoctoral fellow at MSU and the study’s lead author. “These results raise that possibility.”

The findings were published in the most recent edition of Nature Communications.

“Placebos are all about mind over matter,” says Jason Moser, co-author of the study and professor of psychology at MSU. “Nondeceptive placebos were born so that you could possibly use them in routine practice. So rather than prescribing a host of medications to help a patient, you could give them a placebo, tell them it can help them, and chances are if they believe it can, then it will.”

To test the nondeceptive placebos, the researchers showed two separate groups of people a series of emotional images across two experiments. The nondeceptive placebo group members read about placebo effects and were asked to inhale a saline solution nasal spray. They were told the spray was a placebo that contained no active ingredients but would help reduce their negative feelings if they believed it would.

The comparison control group members also inhaled the saline solution but were told that the spray improved the clarity of the physiological readings the researchers were recording.

The first experiment found the nondeceptive placebos reduced patients’ self-reported emotional distress. The second showed that nondeceptive placebos reduced electrical brain activity reflecting how much distress someone feels to emotional events, with the reduction occurring within a couple of seconds.

“These findings provide initial support that nondeceptive placebos are not merely a product of response bias – telling the experimenter what they want to hear – but represent genuine psychobiological effects,” says Ethan Kross, co-author of the study and a professor of psychology and management at U-M.

The researchers are following up on their data with a nondeceptive placebo trial for COVID-19-related stress.

The study is available here.

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