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When people feel pain or an itch, they typically try to ignore it or distract themselves — operating on the unspoken assumption that the sensation will fade on its own.

But new research suggests that doing so may actually worsen inflammation. A study published in the journal Nature Human Behaviour found that the brain and a person's attention can alter the immune system's inflammatory response.

Researchers found that when participants tried to divert their attention away from an itch, the extent of inflammation — measured by skin redness and swelling — grew larger and lasted longer. Conversely, when participants focused on the sensations at the inflamed site, inflammation subsided more quickly.

The findings add to a growing body of research suggesting that the brain and the immune system, long regarded as separate systems, are in fact closely connected. Abnormal immune activity and inflammation have been linked to a range of mental and neurological conditions, including schizophrenia, depression, long COVID and dementia. Recent studies have even shown that simply seeing someone who appears to be infected can trigger an immune response in the brain.

Jonathan Kipnis, a professor of pathology and immunology at Washington University School of Medicine in St. Louis who studies neuroimmune interactions, said the two systems are in constant communication. "The brain is involved in the survival of the individual, and the immune system is also involved in survival," he said. "Since both exist for survival, it is only natural that they are connected."

Liron Rozenkrantz, a senior researcher at Bar-Ilan University's Azrieli Faculty of Medicine in Israel who led the study, and her team induced inflammation in 57 participants by placing a drop of histamine on their forearms and pricking the skin with a needle. Rozenkrantz described the reaction as similar to "a severe mosquito bite."

To minimize the influence of individual differences, the researchers had the same participants go through two conditions, each once. In one condition, participants were asked to focus on a screen to distract themselves from the itch. In the other, they were asked to focus on the sensations at the inflamed site without looking at or touching it.

Swelling and redness decreased more when participants directed their attention to the inflamed area. In contrast, <style ref="s0">when participants focused on another task, inflammation worsened in 90 percent of them, and the degree of swelling and redness was about 50 percent greater</style>. After 20 minutes, about 90 percent of those who had focused on the inflamed site saw their swelling stabilize or decrease, compared with only 46 percent of those who had redirected their attention.

The researchers said the results suggest that signals from the brain may help regulate the immune system's inflammatory response. "It was very impressive that the effect was consistent across the majority of participants," Rozenkrantz said.

Kevin Tracey, president and CEO of the Feinstein Institutes for Medical Research, said <style ref="s1">"thinking 'this inflammation is hurting me' can actually cause more signals related to the inflammation to enter the nervous system."</style> The nervous system may then send out stronger signals to turn off the inflammation, he added.

The study has limitations, however. Kipnis said it is difficult to conclude that the brain directly controlled the immune system, as the researchers did not directly measure immune cells or related molecules. The experiment also involved only temporary inflammation that did not require the body to fight a pathogen. Rozenkrantz and her team plan to investigate how attention shapes the body's response in cases of chronic inflammation or when the immune system is actively fighting an infection.


mokiya@heraldcorp.com