Lack of control and unpredictability can cause stress. Stress can be defined as an environmental or physiological challenge that brings about a stress response. A stress responses is a suite of changes in the body that is brought about by the perception of a threat or challenge. Stressors elicit a stress response; these include excessive noise and heat, restraint, infection, predators, change of environment, overcrowding and isolation. When a stressor is perceived by the brain, nerve signals are sent to parts of the body such as the heart, lungs and gut and to glands such as the adrenal gland that secretes the hormones adrenalin and cortisol. There are two kinds of stress – acute or short term stress and chronic or long tern stress.
Acute stress is essential for survival and enables a speedy removal from danger. In response to a stressor, adrenalin is initially produced and has a short term action. It raises the heart rate and blood pressure, increases lung capacity, raises blood glucose levels, and decreases digestive and reproductive activity. This enables resources (glucose, oxygen) to be channelled to muscles and the brain at the expense of non-essential activity e.g. gut, reproductive system. Alertness increases, memory and the ability to learn is enhanced and pupils dilate to enable clearer vision. Cortisol has similar effects to adrenalin but these are slower and more prolonged and in the short term they are beneficial. Cortisol releases glucose and fatty acids from body stores and makes the blood more energy rich, enhances the immune system and stimulates endorphin release to blunt pain.
Chronic or long term stress is harmful to health owing to the continued release of cortisol. Chronic stress can cause cardiovascular disease, stomach ulcers, weight loss, and suppression of the immune system, loss of sexual function, memory loss and lowered life expectancy. There is a link between stress levels and socio-economic gradients. Those at the top of the social hierarchy have longer life expectancy and better health than those at the bottom even in wealthy countries with a free health service and no absolute poverty. Life is more stressful for those lower down the socio-economic hierarchy mainly because they have less control over what they do, when they do it and where they do it and they are more subject to unpredictable change.
Is stress always bad for you? No, if it is short term – it is essential for survival. Yes, if it is chronic, but it can be managed and alleviated with stress management strategies.