Stress is a type of alarm reaction, involving heightened mental and bodily states - it is both a psychological and a physiological response to the environment. Your brain produces a stress reaction when you are in a situation that is physically or mentally demanding.
Stress is normal. Some stress is good for you - it keeps you alert and protects you in times of danger or when you need to act or think quickly. Physical training to keep fit places stress on your body, but that stress has a beneficial effect (provided you don't overdo it!).
Feeling a bit stressed about exams is normal - it may help you to focus your energy into revising well. Prolonged and unwanted stress, however, may lead to mental and physical health problems.
When psychologists talk about 'stress' they may refer to the causes of stress reactions ('stressors') or to the effects of stress reactions on our physical and mental functioning.
Psychologists are interested in causes of stress, ways in which stress affects us and stress management.
Your brain is on the look out for anything that threatens to upset its equilibrium - if there are serious 'stressors' around, it triggers off an 'alarm reaction'.
The alarm reaction prepares your body for action - sometimes known simply as the 'fight or flight reaction'. Stress hormones and the action of the sympathetic nervous system prepare your body for vigorous muscular activity as follows:
So, what if you are not in a situation in which it's OK to suddenly get up and run a four-minute mile round the block?
Well, that's when various unpleasant effects may set in, such as throbbing headaches, irritability, tense neck and shoulders, dried up mouth and butterflies in the stomach. Sound familiar? Most people experience this sort of stress sometimes.
The flow diagram below shows what goes on in the body when the brain detects a potentially harmful 'stressor'
All the stress hormones circulating in the bloodstream and the neural effects of the sympathetic nervous system combine to create the 'fight-or-flight' response.
The hypothalamus plays a key role in the control of the endocrine system. There is a complex feedback system between the hypothalamus, sympathetic nervous system, the pituitary gland and the secretions of the adrenal glands.
The adrenal glands are found on top of your kidneys - they secrete epinephrine (otherwise known as adrenaline) and other 'stress hormones'. The activity of your adrenal glands is crucial to your mood, energy levels and ability to cope with stress.
In extreme cases of stress your adrenal glands may become enlarged, the spleen and thymus glands may shrink and deep bleeding stomach ulcers may occur. (Not very nice!)
Selye pioneered stress research in the 1950s - he came up with the idea of the general adaptation syndrome. This is a collection of symptoms shown by the body in response to any stress - physical illness such as infection or injury, or stress due to psychological factors. The key thing is that it is 'general' - a non-specific response to any illness.
The three main phases of the 'general adaptation syndrome' are:
1) Alarm Reaction
2) Resistance Stage
The idea of the 'general adaptation syndrome' was drawn from very early research on stress.
It has been criticised because it was based on work with animals and tells us nothing about psychological or emotional factors.
Physiologists have also argued that there may well be different physiological responses to different stressors and not just one 'general' syndrome.
In other words, Selye's model to explain stress is too simple - in reality, the process is more complex.
Research has shown strong links between prolonged stress and many disorders, mentally and physically. The immune system is easily affected by stress.
You should be aware that stress might lead to behaviour, such as smoking or overeating, which increases the risk of serious illness - so the link with the original source of stress is indirect.
The incidence of cancer has been correlated with high stress levels.
Jacobs and Charles (1980) found that cancer patients - for example, child cancer patients, often suffered high levels of stress before the diagnosis of their illness.
Tache et al (1979) found the incidence of cancer to be higher in those with a poor 'social support network' such as the widowed, divorced or separated.
It is difficult to rule out that undetected, developing cancer might cause stress, rather than stress due to external factors leading to cancer.
The 'risk factors' linked with cardiovascular disease include diet, smoking, obesity, lack of exercise (or over-exercise) and stress. Indeed, stress may well be a cause of other behavioural factors.
Men are more susceptible to heart disease than women, even when diets are matched. Could it be that men have more stressful lives than women such as more job-related stress?
For example, it was found that among 40 male tax accountants, blood cholesterol and clotting speeds were at dangerous levels in April (The end of the financial year)!
Perhaps women in this type of work would also show similar signs of stress. There have not been many studies into women's stress levels, but it is worth noting that the incidence of stress-related behaviour such as smoking is increasingly amongst women.
Here's how stress might lead to heart disease: Stress-related behaviour such as smoking or eating lots of fatty foods will speed up the hardening of the blood vessels stage…