The warning signs of stress are often denied, ignored or not recognised. The consequences of chronic stress that is not addressed leads to disease.

Chronic stress is a causative factor of diseases of the cardiovascular system, including hypertension, stroke and heart disease; a compromised immune system which can lead to infections, allergies or even cancer; and gastrointestinal conditions such as ulcers and irritable bowel syndrome.

A new branch of medicine, psychoneuroimmunology (PNI), looks at the connection between mind and disease, an important concept for stress which has both physical and psychological components. An important point to appreciate is that stress is difficult to measure and evaluate objectively.

Stress and the cardiovascular system

The adrenergic overdrive of stress causes the heart and blood vessels to work harder and if this strain continues, predisposes to heart disease and stroke. The direct link between stress and heart disease is difficult to establish as there are many risk factors intertwined, such as smoking, high blood pressure and being overweight. Stress increases these lifestyle heart disease risk factors, which have a large impact on risk. Once heart disease is established, emotional stress can be the immediate cause of clinical symptoms.

What actually happens?

At times of stress, blood pressure rises and the blood which already sprints from the heart, is travelling at an even greater pace. The branches of the blood vessels become more vulnerable to damage under this strain, more lipids accumulate so narrowing arteries and leading to angina, heart attacks and stroke. Unstable atherosclerotic plaques rupture and expel their contents under increased blood pressure, causing blood to clot and consequently blocking blood supply to the heart.

In addition, as a survival mechanism under stress, adrenaline causes blood to thicken and more likely to clot, in case of extensive bleeding. This only compounds the effect on the cardiovascular system, hampering the passage of fast flowing blood, causing it to help block arteries. The increased amount of circulating fat, due to the release of adrenaline, is deposited in the plaques.

Blood pressure - short-term stress, either mental or physical, temporarily increases blood pressure. But the effect of long-term stress and anxiety on blood pressure is less clear. It has been suggested that sustained high blood pressure following prolonged stress may thicken and stiffen artery walls, reducing blood flow and contributing to hypertension. But it has not been established that repeated stresses lead to a sustained higher blood pressure at rest.

Overweight - a risk factor for heart disease and hypertension. Physical and emotional stress enhances anti-diuretic hormone (ADH) output, which results in water retention and weight gain. In addition, the tendency to comfort eat during times of stress leads to an overweight condition.

Smoking - smoking and stress are closely linked, not least because many people smoke specifically to help them relax. Others use cigarettes as a stimulant, to help them enhance their performance.

Stress and the Immune System

On an everyday level, you are probably aware that when you feel a bit run down, youre more likely to catch everything thats going. But why does this happen and how does stress affect the immune system?

A natural reaction to stress is the hormonal surge from the pituitary and adrenal glands along with increased white blood cell activity, in order to protect from infection.

The cells of our immune system release chemicals to combat the infection. The chemicals stimulate the brain to feed back on the immune system through the nerves that feed the components of our immune system, the thymus gland, lymph nodes and bone marrow. The result is the increased production of white blood cells, which fight infection.

This reaction is beneficial for short term stress, but during chronic stress, the levels of growth hormone, prolactin and white blood cells decrease. Effectively, stress compromises the immune system, making us more vulnerable to infection.

When corticosteroid hormones are released into the bloodstream during times of stress, they attach to various receptors on cells within the immune system, depressing the cells ability to function optimally. They not only prevent the formation of T lymphocytes (white blood cell that attacks antigens such as a virus), but may also destroy some lymphocytes. In addition, they inhibit the release of interleukins and interferons, an essential component of the immune systems armoury.

Furthermore, levels of growth hormone are restricted during periods of stress, which in turn reduces white blood cell activity and our ability to produce antibodies, the mainstay of the immune system.

The study of stress and the immune system is difficult due to the many variables that may be relevant in ways that are not immediately obvious. For example, people who are socially isolated or the bereaved have poorer immune function and are more prone to disease than those who are not socially isolated or bereaved. But it is difficult to discount other variables that could be relevant, such as eating a poor diet.

Stress and cancer

An extrapolation of stress compromising the immune system leads us to cancer, as the immune system also destroys cells that could develop into cancers. The suggestion that stress is linked to cancer is scientifically difficult to prove, as the disease is so complex. Many cancers take years to develop and it is not easy to ascertain exactly when the cancer started, making it difficult to establish whether stress played a role in its initiation. No clear link has been established. See the Latest Research section for further details.

Stress and diseases of the gastrointestinal tract

The gastrointestinal tract, through its autonomic nerve supply, is closely related to brain centers concerned with expression of emotion. Combined with our resources being diverted from digestion during times of emotional stress, it is clear to see how stress can contribute to diseases of the gastrointestinal tract such as dyspepsia (any gastrointestinal symptom associated with ingestion of food e.g. nausea, heartburn, distension, indigestion), ulcers and irritable bowel syndrome.

Ulcers

Stress has long been associated with duodenal and peptic ulcers, whereby the stomach lining gradually erodes and becomes more susceptible to the stomachs acidic juices. It is not fully understood how they are linked, but the following sequence of events provides insight into what occurs.

When under stress, the body reduces the amount of acid secretion in the stomach, as the parasympathetic nervous system slows and stops digestion. The stomach lining, which is normally thick and mucous-like, lowers its defences as this lack of acid minimises the need for the lining to protect itself. In addition, the secretion of prostaglandins is reduced, the hormone related substances that help repair the damage to the stomach lining. Hence when stress levels have subsided, your stomach starts to secrete acid as usual, and the stomach lining is inevitably more vulnerable to the effects of acid, predisposing to an ulcer.

Most ulcers are caused by a bacterium called Helicobacter pylori, which can live naturally in our stomach. Figures show that up to 20% young adults and about 50% of those over 50 are infected in the West. In some cases, Helicobacter pylori starts to infect the cells in the stomach lining causing inflammation, preventing the stomach lining from defending itself against stomach acid. Lowered immunity to infection at times of stress increases the bacterium, so increasing the risk of an ulcer.

03/06/2009