The main function of the immune system is to protect the body from infectious agents such as viruses and other toxins. The immune system can fail us in two ways-either by becoming under-vigilant, letting infections enter the body, or over-vigilant, so that it is the immune system itself, rather than an infectious agent that causes illness.
Most studies of the relationship between stress and the immune system have focussed on acute(i.e. short lived) stressors and have found a decrease in immune cell function.
Selye (1956) developed a model called the General Adaptation Syndrome (GAS) which explained the short-term effects of exposure to stressors. He proposed that all stressors cause the same biological response in all animals and humans. The GAS has 3 stages.
In the first Alarm stage, the presence of a stressful event is registered. This can be a threat from outside or a physical stressor, such as injury or illness affecting the body. Adrenaline is released and the heart rate goes up. Muscle tension, blood sugar and the pain threshold increases.
In the second stage of Resistance, the body’s stress response is fully activated and is apparently coping with the stressor. However, resources are still being used up faster than they are being restored and so a person may remain irritable and “on edge”.
However, if the stressor is long lasting, the body enters the third stage of Exhaustion. Selye felt that hormone reserves were depleted and it is at this point that stress-related conditions such as ulcers, depression and anxiety may develop as stress systems become exhausted.
Another research study into the relationship between stress related illness and the immune system was carried out by Kielcot-Glaser et al (1984). They performed a natural experiment to investigate whether the stress of short term stressors, such as important exams, had an effect on the