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Stress may be detrimental to fighting off infections

A new study led by the Icahn School of Medicine at Mount Sinai has found that acute stress can be detrimental to fight off infections, such as Covid-19 or influenza, and increases the chance of dying in mouse models. These findings connecting the brain to the immune system clarify how stress modulates the body’s responses to viruses, making infected organisms more susceptible to severe illness and worse overall outcomes. 

In the first part of the study, researchers analyzed the immune systems of relaxed and stressed mouse models. Within just a few minutes, mice experiencing acute stress showed major changes in their immune systems, compared to those in the relaxed group. By using sophisticated tools such as chemogenetics and optogenetics, the scientists found that, under stressful conditions, neurons from the paraventricular hypothalamus were prompting immune cells, or leucocytes, to migrate from lymph nodes into the blood and bone marrow.

In a second step, the researchers infected mice with SARS-CoV-2 and influenza and found that those in the relaxed group were able to fight infection better and eliminate the virus from their organism more easily. The stressed mice became sicker and had a higher death rate after infection. 

“This work tells us that stress has a major impact on our immune system and its ability to fight infections. It raises many questions about how socioeconomic factors, lifestyle, and environments we inhabit control how our bodies can defend themselves against infection,” said study lead author Filip Swirski, the director of the Cardiovascular Research Institute at the Icahn School.

This study is an important example of how the brain controls inflammation triggered by immune responses to infections, and how acute stress can lead to worse outcomes when fighting viral infections. These findings should prompt physicians to pay better attention to patients’ mental states, including stress levels and sleeping patterns, and devise therapeutic measures that take into account pre-existing mental conditions.

“Moving forward, we will need to better understand the long-term effects of stress. It will be particularly important to explore how we can build resilience to stress and whether resilience can diminish stress’s negative effects on our immune systems,” concluded Dr. Swirski. 

The study is published in the journal Nature.

By Andrei Ionescu, Staff Writer

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