Stress (biology)

This picture shows an exaggerated expression of stress.

Stress (roughly the opposite of relaxation) is a medical term for a wide range of strong external stimuli, both physiological and psychological, which can cause a physiological response called the general adaptation syndrome, first described in 1936 by Hans Selye in the journal Nature.

Stress and its effects

Selye was able to separate the physical effects of stress from other physical symptoms suffered by patients through his research. He observed that patients suffered physical effects not caused directly by their disease or by their medical condition.

Selye described the general adaptation syndrome as having three stages:

alarm reaction, where the body detects the external stimuli
adaptation, where the body engages defensive countermeasures against the stressor
exhaustion, where the body begins to run out of defenses

There are two types of stress: eustress ("positive stress") and distress ("negative stress"), roughly meaning challenge and overload. Both types may be the result of negative or positive events. If a person both wins the lottery and has a beloved relative die on the same day, one event does not cancel the other — both are stressful events. (Note that what causes distress for one person may cause eustress for another, depending upon each individual's life perception.) When the word stress is used alone, typically it is referring to distress.

Serenity is defined as a state in which an individual is disposition-free or largely free from the negative effects of stress, and in some cultures it is considered a state that can be cultivated by various practices, such as meditation, and other forms of training.

Stress can directly and indirectly contribute to general or specific disorders of body and mind. Stress can have a major impact on the physical functioning of the human body. Such stress raises the level of adrenaline and corticosterone in the body, which in turn increases the heart rate, respiration, and blood pressure and puts more physical stress on bodily organs. Long-term stress can be a contributing factor in heart disease, high blood pressure, stroke and other illnesses.

The Japanese phenomenon of karoshi, or death from overwork, is believed to be due to heart attack and stroke.

Stressors

Any factor that causes stress is called a stressor. There are two kinds of stressors: processive stressors and systemic stressors.

Processive stressors are elements in the environment (for example, elevated sound levels or intense light) perceived by the organism as potential dangers. These do not cause damage directly, but are processed in the cerebral cortex. The processed information is then sent via the limbic system in the hypothalamus, where they activate the supreme centers of the autonomic nervous system. This results in the fight-or-flight (or sympathetico-adrenal) response.

Systemic stressors cause a disturbance in the organism's homeostasis, as well as tissue necrosis, hypotension and/or hypoxia. Often both types of stressors occur simultaneously. They are usually accompanied by pain and/or intensive emotions.

Coping with stress

Individuals can respond very differently to the same stressor; any given situation can cause eustress in one person and distress in another. This happens because of differences in physiology and life circumstances, as well as different methods of stress management. Methods of coping that work well in childhood situations often become ingrained and habitual, and often follow the child into adulthood. In the adult world, these skills can be quite inappropriate, and stress heightens as the person clings to obsolete behaviors. However, new skills can be learned, and poor coping methods replaced. There are currently many classes, books, and seminars available to help people develop better habits of managing stress.

Other approaches to dealing with stress include The Alexander Technique, Shiatsu, T'ai Chi Ch'uan, yoga and meditation. For example, when Selye reviewed the physiological changes measured in practitioners of transcendental meditation (TM), he concluded that such changes were the opposite of the body's reaction to stress. The therapeutic effect of TM was most distinct in people whose coping skills were poorly adapted to the stress of daily life.

Finally, a number of psychological and sociological factors have been consistently demonstrated to act as a moderator against stress in the development of chronic psychological or physical disease (such as depression or hypertension). Among these many factors are chiefly: optimism or hope, social support, Socioeconomic status (SES), sense of community, and others.

Neurochemistry and physiology

The general neurochemistry of the general adaptation syndrome is now believed to be well understood, although much remains to be discovered about how this system interacts with others in the brain and elsewhere in the body.

The body reacts to stress first by releasing the catecholamine hormones, epinephrine and norepinephrine, and the glucocorticoid hormones, cortisol and cortisone.

The hypothalamic-pituitary-adrenal (HPA) axis is a major part of the neuroendocrine system, involving the interactions of the hypothalamus, the pituitary gland and the adrenal glands. The HPA axis is believed to play a primary role in the body's reactions to stress, by balancing hormone releases from the adrenaline-producing adrenal medulla and from the corticosteroid-producing adrenal cortex.

Folklore of stress

About the time of Selye's work, the gradual realization dawned that such concepts as anxiety, antagonism, tiredness, frustration, distress, overwork, pre-menstrual tension, over-focusing, confusion, mourning and fear could all come together in a general broadening of the meaning of the term stress. The popular use of the term in modern folklore expanded rapidly, spawning an industry of pop psychology, self-help, personal counselling, and sometimes quackery.

The use of the term stress in serious recognized cases such as those of post-traumatic stress disorder and psychosomatic illness has scarcely helped clear analysis of the generalized 'stress' phenomenon. Nonetheless, some varieties of stress from negative life events, or distress, and from positive life events, or eustress, can clearly have a serious physical impact distinct from the troubles of what psychotherapists call the "worried well". Stress activates the sympathetic nervous system and release of stress hormones including adrenalin/epinephrine and cortisol.

Sympathetic nervous output tends to divert bloodflow to the large muscles - the body 'thinks' it has to run away from something or fight something: the so-called flight/fright syndrome of ancient evolutionary heritage - and bloodflow is correspondingly less to the bowel and other non-muscle organs. We all recognise the effects: dry mouth, motor agitation, sweating, pallor, enlarged pupils and insomnia. Our modern lifestyle tends to cause continual sympathetic nervous system activation with very little opportunity for the parasympathetic (also called 'vegetative') nervous system to activate. When this system is active the bowel and other non-muscle organs get good blood-flow, the pupils constrict, the glands all function well and secrete their various compounds. Absence of parasympathetic activation leads to poor digestion and probably also to poor healing and organ function. It is vital to take time out from our modern lifestyles to allow for rest and proper parasympathetic action in our bodies.

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