When we catch a cold, it’s usually due to a weakened immune system. However, according to a study published in the journal Proceedings of National Academy of Sciences, a weakened immune system isn’t always the culprit. Researchers say stress may also be responsible.

Cortisol--the hormone released when we're stressed--tends to suppress our immune system’s inflammatory response to viruses and bacteria. This is normal. However, chronic stress messes up our body’s inflammatory response even more, making it less sensitive to cortisol. Instead of being suppressed, our inflammatory response is forced into overdrive, which may explain some of our cold symptoms. "They’re unable to regulate the inflammatory response, and therefore, when they’re exposed to a virus, they’re more likely to develop a cold," says lead author Dr. Sheldon to CNN.

In an effort to test the theory, researchers interviewed 276 healthy adults about what stressed them out over the last year. They were then given nasal drops containing a cold virus and were quarantined for five days. Out of the total participants, 39 percent developed a cold. Furthermore, those who became stressed out were twice as likely as the others to fall ill.

For the second leg of the study, researchers tested 79 participants on their ability to regulate their inflammatory response before exposing them to a cold virus. They also tracked down the participants’ production of pro-inflammatory cytokines—chemical messengers responsible for inflammation. Those who initially showed poor inflammatory response produced more cytokines after their exposure to the virus.

Now, the common cold might not be our biggest health problem, but inflammation has also been linked to other diseases. "Because inflammation plays a role in many diseases such as cardiovascular, asthma, and autoimmune disorders, this model suggests why stress impacts them as well," Cohen explains. “Knowing this is important for identifying which diseases may be influenced by stress and for preventing disease in chronically stressed people.”


(Photo by anna gutermuth via Flickr Creative Commons)