It has been known for many years that stress can affect your health but we are only now beginning to fully understand just how stress can affect the body. Some of the myths surrounding stress, such as the fact that stress can lead to ulcers, are being laid to rest and others are now being confirmed.

Many of the more obvious effects of stress such as headaches, muscle tension, a rapid heartbeat, high blood pressure and digestive problems are easily recognized and well known, but there are also a number of longer-term, and potentially serious, conditions that can be caused by chronic stress.

Studies undertaken at the National Institutes of Health and elsewhere for example strongly suggest that stress affects the immune system. Interestingly, these same studies show that the effect can be both positive and negative.

Since one definition of stress is that it is simply a person's 'fight or flight' response to a perceived threat, it can have a positive effect. It can, for example, trigger the release of chemicals which help heal infections from bites. That makes sense if you consider how evolution might have tailored the immune system to deal with these problems.

However, when this particular response persists over an extended period of time, the effects can be harmful and one result is that the immune system actually reduces in effectiveness resulting in a higher susceptibility to infection and a lowered resistance to colds and other virus induced illnesses.

Another result is a general feeling of tiredness and sometimes depression. When a person is stressed for long-periods, a feedback loop is created between the cause of the stress (the belief that it is not possible to solve the problem that is causing the stress) and the effects. This creates a cycle in which the belief becomes a self-fulfilling prophecy.

Chronic stress can also impact your health by compromising you circulatory system. When stress hormones released by the 'fight or flight' trigger are not used up by the physical activity of, for example fighting off infection, they can cause actual physiological stress on the body.

High blood pressure increases the tension on the walls of blood vessels which can lead to tiny tears appearing in the blood vessels. When the body reacts to heal these micro-tears scar tissue can be produced and this decreases the blood flow through the vessels.

If stress levels are extremely high or persist for a long enough period of time then heart attacks can occur. The risk of heart attack is also raised in older people or in people carrying certain genetic characteristics. As the blood vessels narrow, the heart may not be able to deliver enough blood and oxygen at moments of high demand.

It has also been known for a long time that stress can worsen the effects of rheumatoid arthritis and this is now also explained by the effect of stress on the immune system, as there is a proven and well documented link between rheumatoid arthritis and the body's immune system.

Avoiding stress is important for all of us to maintain good health and, fortunately, as we begin to gain a better understanding of stress we are also developing a number of very effective stress relief techniques.