11th April 2012 - Stress has already been linked to a greater risk of depression, infectious diseases and even heart disease. A recent study has looked at how stress could be causing these health problems.
According to the International Stress Management Association UK, stress is "the adverse reaction people have to excessive pressures or other types of demand placed on them."
When those pressures become overwhelming, they lead to stress. A little stress can be a good thing - it is part of the fight or flight mechanism that allows us to cope with a challenge. However, being in a continual state of stress means that body chemicals used to stimulate the fight or flight response are constantly active, and this can have adverse effects on our mental and physical health.
How stress can make you ill
The research study at Carnegie Mellon University, headed by Dr Sheldon Cohen and published in the Proceedings of the National Academy of Sciences, has for the first time been able to establish that chronic psychological stress affects the body's ability to regulate the inflammatory response, which in turn can allow the development and progression of disease.
"Inflammation is partly regulated by the hormone cortisol, and when cortisol is not allowed to serve this function, inflammation can get out of control," says Dr Cohen, a professor of psychology at Carnegie Mellon University in news release.
The study found that prolonged stress decreases tissue sensitivity to cortisol, so it could alter the effectiveness of cortisol to control the inflammatory response. To be more specific, the immune cells don't response properly to cortisol's regulatory effect, so inflammation isn't controlled. It is this runaway inflammation that allows the development of many diseases.
An earlier study by Dr Cohen showed that psychological stress made people more susceptible to developing the common cold, and he used the common cold virus for testing his theory. The symptoms of common cold are not caused by the virus itself, but are a side-effect of the inflammatory response triggered by the body to fight off the virus. The more your body tries to fight off the infection, the more symptoms of a cold you're likely to experience.
In the first study, 276 healthy adults were exposed to a common cold virus after completing an intensive stress review, and were then put into quarantine for five days. Dr Cohen concluded that in those who suffered a stressful event, the stress affected the immune cells? response to hormonal signals that normally control inflammation. These people were unable to regulate the inflammatory response and were more likely to develop cold symptoms on exposure to the virus.
In his second study, Dr Cohen assessed 79 healthy participants and their inflammatory response before exposing them to a cold virus. He monitored the production of pro-inflammatory cytokines, which are chemical messengers that trigger inflammation. In this study, he found that the participants who were less able to regulate their inflammatory response produced more of these chemical messengers when they were infected.
"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," says Dr Cohen. "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 suggests why stress impacts them as well."
He added, "Knowing this is important for identifying which diseases may be influenced by stress and for preventing disease in chronically stressed people."
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