April 3, 2012
Yes, Stress Can Make You Sick. But How?
Researchers, led by Sheldon Cohen, at Carnegie Mellon University have discovered that psychological stress increases risk for depression, heart disease and infectious diseases. And now they know how.
The researchers found that psychological stress causes the body to lose its ability to regulate the inflammatory response. According to Cohen, “Inflammation is partly regulated by the hormone cortisol and when cortisol is not allowed to serve this function, inflammation can get out of control.”He argues that prolonged stress affects the body's ability to regulate the inflammatory response because tissue becomes less sensitive to cortisol over time.
In order to test his theory, Cohen exposed patients to the common cold in multiple studies. Common cold symptoms are not a result of virus exposure, but are an effect of the body´s inflammatory response triggered by the body to fight infection.
The first study consisted of 276 healthy adults who were exposed to a virus that causes the common cold. The patients were monitored in quarantine for five days for signs of infection and illness. Cohen noted that when patients were exposed to a prolonged stressful event, the immune cells lost their ability to respond to hormonal signals that regulate inflammation. Those patients that were unable to regulate the inflammatory response were more likely to develop colds.
In a second study, Cohen screened 79 healthy patients on their ability to regulate the inflammatory response. The patients were exposed to a cold virus and monitored for the body´s production of pro-inflammatory cytokines. Cohen found that patients who were less able to regulate the inflammatory response produced more of the cytokines when exposed to the virus, thus increasing the inflammatory response by the body.
Cohen said, “The immune system´s ability to regulate inflammation predicts who will develop a cold, but more importantly it provides an explanation of how stress can promote disease. When under stress, cells of the immune system are unable to respond to hormonal control, and consequently, produce levels of inflammation that promote disease. Because inflammation plays a role in many diseases such as cardiovascular, asthma and autoimmune disorders, this model suggest why stress impacts them as well.”
The study is published in the Proceedings of the National Academy of Sciences (PNAS).