Stress Related Illness and the Immune System

It is widely thought that stress has a negative effect on the general health of anyone suffering both acute and chronic stress - Cohen et al (1993) carried out investigations to into measuring the effects of the immune system against the level of stress his volunteers reported.

Cohen carried out his investigation by undertaking a ‘natural experiment’ or ‘quasi-experiment’.  He took 394 participants and asked them to complete a questionnaire which recorded the number of stressful situations they had encountered during the past year and also recorded how they felt emotionally during these times i.e. feelings of depression and hostility.  Once collated, the scores were entered into a stress index.

Each of the participants were then exposed to the common cold virus – it was found that 82% of the subjects developed cold symptoms – the people that scored highest on the stress index were found to have suffered most from the cold virus – the conclusion of Cohen’s experiment indicates that high levels of stress and negative emotions have a significantly negative effect on the immune system.

It could be argued that the experiment is unethical due to the fact that the participants suffered the effects of the cold virus for the cause of the experiment, although it does have some ecological validity as the test was carried out in an uncontrolled environment and therefore a similar situation would be likely to arise in real life. The experiment does have some limitations, for instance – its reliability may be questioned due to the fact that each individual’s ability to recall stress levels accurately may differ.

There have been numerous medical and psychological studies investigating the effects of stress on the immune system. These show that the immune system is a collection of cells that travel through the blood stream that move between the tissues and organs fighting off infection and antigens such as bacteria, viruses and cancerous cells.  There are two types of lymphocytes, B cells - which release antibodies into the bodily fluids and fight off invading viruses and bacteria, and T cells – if the invader gets inside a cell the T cells lock onto the infected cell, multiply and destroy it.  When we are stressed the body’s natural ability to produce B and T cells becomes reduced and therefore we become less able to fight off infection and consequently more susceptible to contamination.