Selye’s model of stress is known as the General Adaption Syndrome or GAS. GAS consists of three stages ‘The Alarm Stage’, this is when an organism first encounters a threat, it responds with what is known as the “fight or flight” response, this consists of a, an increase in – adrenaline secretion, respiration rate, heart rate, blood pressure and muscle tension. The digestion rate lowers or decreases, the pupils dilate, a release of stored sugar to give an organism extra energy and an increase in blood coagulability. All of these happen due to the activation of HPA and SAM.
The second stage is resistance, during this stage the body attempts to stabilise any psychological changes that may have occurred in the alarm stage. The parasympathetic ANS is activated and attempts to reduce the heart rate, rebuild stores of sugar etc.
The final stage is the exhaustion stage if the stress cannot be overcome then the adrenal glands become enlarged again, the body’s resources, including hormone levels, become depleted. In a study of rats by Selye they perished as a direct consequence of the physiological changes undergone in their own defence.
In 1981 Riley placed mice on a rotating turntable. He measured the mice’s lymphocyte count over 5 hours and found a marked decrease in the number of lymphocytes. Thus shows that stress can almost immediately affect the immune system. However, a further study showed that this reduction in lymphocytes leads to decreased ability to defend against illness.
In 1995, Kiecolt-Glacier et al compared the rate in a high stress group of women, he used 13 women aged between 47 and 81 years, these women where caring for relatives with Alzheimer’s disease , he used a control group of 13 women in the same age group who were not carers. The two groups were matched on age and income, but not marital status. All participants were given a 3.5mm punch biopsy just below the elbow. The wounds were dressed and treated by a nurse in the same way for each participant. Additionally, the levels of cytokines were measured. The participants were given a ten item perceived stress scale to determine how stressed they actually felt. The complete wound healing took significantly longer in the carers than the control group, on average it took nine days longer to heal.
Other psychologists have also studied the stress and the immune system, Schliefer et al (1983) looked at the functioning of the immune system in husbands who had lost their wives to breast cancer. He discovered that after their loss their immune system functioned less effectively. In 1993, Cohen et al studied how stress affected the likelihood of catching infectious diseases. Participants were 154 men and 266 women. The level of stress in their lives was measured using a psychological stress index (PSI). He then exposed volunteers to nasal drops containing respiratory diseases and used blood measures and clinical observation over the next six days to see if a cold would develop. They found that participants with a lower score on the PSI suffered less from a cold than those who scored higher.
