Stress is the way a person responds to environmental demands or pressures. When stress was first studied in the 1950s, the term was used to explain both the causes and the effects of these pressures. More recently, however, the word "stressor" has been used to mean the trigger that provokes a stress response.

A certain degree of stress is a normal part of every day life; it is when stress becomes constant that it can lead to physical and mental problems. Stress-related disease is caused by excessive and prolonged demands on a person's coping resources.

The symptoms of stress can be either physical or psychological. Stress-related physical illnesses may be caused or at least influenced by stress-related overstimulation of a part of the nervous system that regulates the heart rate, blood pressure and digestive system. Some of these stress-related illnesses include irritable...