Throughout history, very little has been known about the puzzling phenomenon that is the placebo effect; that is, little beyond the fact that people often experience a bewildering improvement in their symptoms (whatever they may be) after being given fake medicine.
Scientists have finally identified the part of the brain responsible for the placebo effect. In research published in the journal PLOS Biology, they reveal that people with higher levels of brain activity in a region known as the right midfrontal gyrus (r-MFG) are far more likely to respond to placebos when undergoing treatment for chronic pain.
The researchers say these findings could allow clinicians to determine whether patients can be treated with "sugar pills" instead of actual medication when they are developing personalized treatment programs.
Hoping to discover how the brain regulates the placebo effect, the scientists used functional magnetic resonance imaging (fMRI) to scan the brains of patients undergoing treatment for chronic knee osteoarthritis prior to giving them a two-week course of placebo medication.
While half the patients claimed they experienced considerable pain reduction during the trial, the other half did not. This enabled the researchers to split the group into placebo responders and non-responders.
Looking at the MRI scans taken at the onset of the trial, the researchers found that placebo responders all had higher connectivity in their r-MFG than the non-responders, indicating that this could be a reliable predictor of how likely a person is to react positively to a placebo.
In a second trial, the researchers gave patients another brain scan before giving them a placebo or a real painkiller called duloxetine, which they had to take for three months.
At the trial’s completion, the researchers were able to predict with 95 percent accuracy which patients were most likely to have responded to the placebo simply by looking at the connectivity of their r-MFG. They also discovered that connectivity levels in a different region of the brain known as the right parahippocampal gyrus (r-PHG) could be utilized to predict how well a patient would react to duloxetine.
“The new technology will allow physicians to see what part of the brain is activated during an individual’s pain and choose the specific drug to target this spot,” said the study’s co-author, Vania Apkarian, in a statement.
“Given the enormous societal toll of chronic pain, being able to predict placebo responders in a chronic pain population could both help the design of personalized medicine and enhance the success of clinical trials,” added co-researcher Marwan Baliki.