Biological basis of placebo effect discovered

Oleg Lischuk, N+1

American scientists have discovered an area of the brain responsible for the response to the use of placebo. In the experiment, the activity of this area and its neuronal connections helped to reliably predict in which patients the placebo would be effective, as well as the magnitude of this effect. The results are published in the journal PLOS Biology (Tétreault et al., Brain Connectivity Predicts Placebo Response across Chronic Pain Clinical Trials).

The placebo effect is a well–known phenomenon, consisting in the fact that the administration of a drug that does not contain an active substance has a tangible effect. It is most pronounced in chronic pain and neurological disorders. Despite the fact that this effect is used by doctors and taken into account when conducting controlled clinical trials, its biological nature has not been sufficiently studied.

To fill this gap in knowledge, the staff of Northwestern University in Chicago conducted a series of experiments on volunteers with chronic pain syndrome caused by osteoarthritis. Before starting therapy, all participants underwent functional MRI (fMRI) of the brain at rest, which allowed determining the baseline level of activity of various brain regions.

At the first stage of the experiments, 17 patients were prescribed a placebo as an analgesia, and the volunteers, unlike the doctors, did not know about it. In eight of them, the treatment was effective. Comparing the response to placebo with the results of fMRI, the scientists concluded that it is most closely related to the activity and density of neuronal connections of the right middle frontal gyrus of the brain.

The area of the brain responsible for the placebo effect (large red-yellow area)

39 participants in the second experiment, this time double–blind (in which neither the doctor nor the patient knows in advance what they are taking), were randomly divided into two groups after fMRI: one received a placebo for three months, the other received the antidepressant duloxetine, effective for chronic pain. The pre-determined activity of the right median frontal gyrus made it possible to correctly predict the response to placebo in 95 percent of cases.

Modeling the placebo effect in volunteers who received duloxetine, scientists found that in some of them (6 out of 19) the active drug enhanced the predicted placebo effect, and in others (also 6 out of 19) it weakened it. The simulation also revealed the area of the brain responsible for the response to duloxetine after the introduction of the correction for the placebo effect – it turned out to be the right parahippocampal gyrus.

The results obtained confirm that the placebo effect has a biological basis. In addition, they allow using fMRI to predict the strength of this effect in a particular patient and its role in the action of active drugs, which can improve the accuracy of clinical trials, the researchers write.

Previously, scientists were able to confirm the effectiveness of placebo in Parkinsonism at the neural level and show that the placebo effect can improve the results of intelligence tests. Also, studies have shown that in some conditions, a placebo remains effective, even if the patient knows that he is taking a "dummy".

Portal "Eternal youth" http://vechnayamolodost.ru  01.11.2016