The placebo effect is undoubtedly one of the biggest medical mysteries, with countless studies and anecdotal reports indicating how positive expectations can bring about physical relief from symptoms. Though evidence suggests that mental positivity is largely mediated by the brain’s reward center, exactly how this affects the body’s physiology is still very poorly understood. However, new research may have brought us one step closer to disentangling this complex psychosomatic link, by revealing how stimulation of the reward center causes the body’s immune system to become mobilized.
It’s worth pointing out that when it comes to healing the body, positive thinking is only helpful up to a certain point, and there is no evidence to suggest that attitude alone can cure serious illnesses without medical intervention. Nevertheless, several documented cases have helped to showcase the power of the mind in aiding the physical recovery process.
The idea that the connection between thought and immunity could be mediated by the reward center makes a lot of evolutionary sense. After all, we are most exposed to pathogens when doing pleasurable things like eating or having sex, so it’s logical to think that we may have developed a psychosomatic defense mechanism whereby the immune system automatically becomes mobilized when the brain’s reward center is activated by these sorts of activities.
To investigate this link, the researchers bred mice with designer receptors in a brain region called the ventral tegmental area (VTA), a key part of the reward system. Describing their work in the journal Nature Medicine, the study authors explain how this allowed them to easily stimulate the mice’s reward centers, leading to a number of noticeable changes to their behavior such as an increased tendency to socialize.
More to the point, this also led to an increase in the number of receptors on the surface of certain white blood cells in the animals’ spleens, indicating that their capacity to fight off infections had become enhanced. To confirm this, the researchers then injected the mice with E.coli, finding that these bacteria were more readily destroyed in the bodies of VTA-activated mice than in control mice.
Image: The white blood cells of VTA-activated mice became more effective. royaltystockphoto.com/Shutterstock
They then removed some of the white blood cells from the rodents and placed them in a petri dish with E.coli. Once again, the cells extracted from mice that had had their VTA stimulated were more effective at stopping the bacteria from proliferating than those from non-stimulated mice.
According to the researchers, this provides clear evidence of a “causal relationship between the activity of the VTA and the immune response to bacterial infection.” Perhaps most impressive of all is that this immune response appears to be long-lasting rather than fleeting, since one week after the mice were injected with E.coli, those whose reward centers had been activated were found to have 86 percent more E.coli-specific antibodies in their blood serum.
In a statement, study co-author Asya Rolls said that this finding could provide a platform for harnessing the power of the reward center, and “might one day lead to the development of new drugs that utilize the brain's potential to cure.”
E.coli colonies were diminished in the bodies of VTA-activated mice. martynowi.cz/Shutterstock