Plenty of research measures the health impact of stress and negative feelings, says Erica Sloan, a biologist at Monash University in Melbourne, Australia. But the potential for immune activity to shift in response to positive influences through the brain’s reward center—“that’s what I think is really exciting,” says Sloan, who studies neural-immune activity in cancer but was not involved in the present study.
The notion that the brain talks to the immune system isn’t new. One of the most compelling examples is the placebo effect—the centuries-old observation that sugar pills can work as well as evidence-based medicine in some people. For years scientists have tried to unravel the biology behind this mysterious phenomenon.
Clues emerged in brain imaging experiments published a decade ago. Those analyses revealed that the same reward circuit activated by food, sex and social interactions (as well as gambling and addictive drugs) is also turned on in people who respond to placebos. Puzzling over those data, researchers in Israel turned the mind-body question into an easier-to-measure physiological one: Would activation of the reward circuit have any effect on the immune system?
It seemed fair to assume positive thoughts and emotions would alter the activity of neurons in the brain. “And neuronal activity is something we can manipulate,” says biologist Asya Rolls of Technion-Israel Institute of Technology, who was co-senior author of the current study.