Why stress disorders can lead to physical disease
By Liz Lockhart
We all know that if we suffer from prolonged periods of stress this can adversely affect the body as well as 
the mind. It has been established that stress is associated with a higher risk of several physical disorders including heart disease and depression, as well as infectious diseases.
It has been unclear just why stress should impact on our physical health, however, a recent study has set out to find the answers to this.
Led by Sheldon Cohen of Carnegie Mellon University, a team of researchers has found some of the answers to this problem. The findings of this study suggest that chronic psychological stress can lead to the body being unable to regulate the inflammatory response.
This research demonstrates, for the first time, how the effects of psychological stress on the ability to regulate inflammation, can lead to physical disease.
Dr. Cohen said ‘Inflammation is partly regulated by the hormone cortisol and when cortisol is not allowed to serve this function, inflammation can get out of control. Cohen further suggests that prolonged stress causes a decrease in tissue sensitivity to Cortisol as a result of the reduction of efficiency of cortisol to regulate this inflammatory response. When inflammation becomes uncontrolled, it is believed to promote the onset and progression of several physical diseases.
Cohen, through his earlier work, has demonstrated that individuals suffering from psychological stress are more likely to develop the common cold. He used the example of a common cold as it is not caused as a result of a virus. Common colds are a side effect of the inflammatory response that is triggered when the body fights infection. This demonstrates that the greater the body’s inflammatory response to the virus, the greater the chance of having the symptoms of a cold. When exposed to the virus, those with who are unable to regulate their inflammatory response are more likely to have a cold.
Cohen and his researchers assessed 79 participants to determine their ability to regulate the inflammatory response. They were then exposed to a cold virus. The participants were then monitored for the production of pro-inflammatory cytokines. These are the chemical messengers which trigger inflammation.
It was found that in those individuals who had less ability to regulate the inflammatory response, (as assessed prior to the exposure to the virus) produced a larger number of pro-inflammatory cytokines when they became infected.
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 may diseases such as cardiovascular, asthma, and autoimmune disorders, this model suggests why stress impacts them as well.’
Cohen concluded ‘Knowing this is important for identifying which diseases may be influenced by stress and for preventing disease in chronically stressed people.’
The study findings are available in the publication Proceedings of the National Academy of Sciences.
