It is generally agreed within the medical community that such things as raised blood pressure, rapid heartbeat, a rise in blood sugar level and a lower digestive rate can all result from stress. There is also general agreement that, if stress lasts for any period of time, it can lead to irritability and individuals will generally become more impatient and more quick-tempered. It is also likely that an individual will experience increasing difficulty in coping with the present and develop a fear of the future, as well as finding it harder to concentrate and more difficult to make decisions.
There is a clear connection between these physical and psychological effects. The hypothalamus and the pituitary gland, both located within the brain, released a substance known as ACTH (adrenocorticotropic hormone) which stimulates the adrenal gland to release cortisol. Cortisol is naturally present within the body and its levels rise and fall during the course of a normal day, however, it is an excess of cortisol which is largely responsible for the "flight or fight" response which is commonly seen in cases of stress.
This can also lead to many of the common physical symptoms of stress including tension in the muscles of the neck, as well as stomach and bowel problems. There is also evidence to suggest that persistent stress can lead to a weakening of the immune system and can contribute to such things as frequent colds.
High levels of stress can also result in cognitive problems with a shortened attention span and less efficient memory recall. It becomes more difficult to concentrate on the daily challenges of life in a rational way and emotions can start to run high, leading to moodiness and unreasonable anger.
In more extreme cases stress can result in depression, apathy, crying for no particular reason, an increased fear of failure and the general feeling of doom and despondency.
Stress will also often set up a vicious cycle between "I must" and "I can't". The loss of confidence in one's own ability to deal with life's challenges becomes a self-fulfilling prophecy and, on the one hand, you know that you must do something but, on the other hand, you feel that you simply cannot.
The secret to combating these effects of stress lies in being able to focus your attention on the factors that lead to stress, to evaluate them realistically and to keep a sense of perspective about their consequences. If you can do this then you will clearly reduce the occasions on which a minor problem might lead to major stress.