The Impact of Stress on the Immune System
The study of the physiology of stress as a discipline of scientific
inquiry began in 1936 with a Canadian investigator, Hans Selye, who
adopted the term "stress", used until then only in engineering to
describe forces acting on metals, to characterize the response of the
human body to a strong stimulus (Jerram, 2003.) Today, stress is invoked
with increasing frequency as the cause of or contributing factor to
physical and mental disorders.
 Stress, per se, is not a scourge of the human body but a necessary and
vital defense mechanism. The physiological response we call stress
allows the healthy body to face immediate threats, real or perceived. In
essence, stress prepares the organism for "fight or flight". Problems
arise when the stress response becomes maladaptive. Now classic clinical
studies have demonstrated that the chronic activation or the chronic
repression of the normal stress response can compromise the state of
health and cause diseases that can be directly traced to stress
(Eysenck, 1997). The normative or maladaptive stress response is
conditioned by personal, psychological and social characteristics. Some
individuals are more vulnerable than others to diseases from stress
since they may be daily and chronically exposed to stressor that put an
unusual burden on their physiological coping abilities (Noriyuki,
Yoshiharu, & Nozomu, 2001).
At the most fundamental level, the natural stress response may be
induced by a physical change (physical inducer) such a sensation of cold
or warmth, or by a thwarted expectation or intense mental activity
(psychological inducer) (Gorski, 2002). When the body’s natural stress
response is activated by a real or perceived threat, glucose, which is
the principal source of energy of the body, is mobilized from its normal
storage locations. The blood, transporter of glucose and oxygen, diverts
it from certain organs such as the skin and the intestine, and quickly
ferries it to organs essential to face the emergency: the heart, the
muscles, and the brain. The variation of the blood flow is put into
effect in part through the constriction of some vessels, the expansion
of others and the increase in heart beat. At the same time, cognitive
processes are enhanced (to facilitate the processing of information
relative to the threat) and the perception of pain is attenuated by the
secretion of endorphin (Firdaus, 2002). All physiological activities
that are not of immediate benefit are delayed; growth, reproduction, and
digestion, among others, which are processes requiring much energy and
of no immediate value against the threat, are inhibited.
In addition to the mobilization of glucose to provide energy, the body’s
response to stress causes the secretion of certain hormones and the
inhibition of others. Certain alterations of T and Natural Killer (NK)
cells have been observed and associated with hypothalamic and
hippocampus lesions (Vivier, Nunès, & Vély, 2004); the functionality of
the lymphatic cells is influenced by hormones and neurotransmitters
released under stress (Pardoll, 2001); the lymphocytes, through the
release of cytokine and interleukin 1, influence the neuroendocrine
system; the well documented effects of interleukin 1 are fever, increase
of the level of the glycocorticoids, stimulus of the hypothalamic
secretion of CRH, hypothalamic secretion stimulus of ACTH and endorphin;
the thymus secretes at least four substances (humoral thymic factor,
thymopoietin, thymulin, thymusin) that have an effects on the immune
system and on the neuroendocrine system (Cooney, 1998); peptides of
central nervous system and peripheral nervous system are mobilized to
enhance or inhibit the body’s immune functions. Finally, at the cellular
level, in conditions of stress, certain proteins are synthesized whose
physiological function is to repair any damages that the impending
threat may cause to the body (Glaser, 2000).
This complex response to adverse changes or stressors represents a
fundamental mechanism of defense and is intended to be temporary. After
the threat passes, the body gradually returns to its pre-stress
condition, and hormone levels are reduced accordingly. The inescapable
unity of body, spirit and psyche, and their intimate correlation, point
to the need to maintain the equilibrium that naturally exists between
the endocrine system, the autonomous nervous system and the immune
system. This implies that when the stress response is triggered, it
arises, peaks and normalizes in a natural ebb and flow. This optimal
capacity for arousal, action and return to homeostasis is the epitome of
well-being.
The immune system appears to be the most reactive to stress-inducing
stimuli and unexpected changes (stressors) that come from the outside
(Segerstrom & Miller, 2004) and the most susceptible to damage from a
sustained and unremitting stress response. The stress-inducing or
stress-maintaining stimuli or changes may be of an acute nature (death
of a loved one, loss of a job) or more long-lasting (living in an
unpleasant atmosphere, interpersonal difficulties with colleagues, or
difficulty in adjusting to a new school).
Research studies have shown that continue exposure to stressors and a
chronically activated stress response can have the effect of lowering
the immune defense of the human body (Courtnenay, 2000). This effect is
mediated by the response to those stressors of the autonomous nervous
system, which causes the endocrine system to secrete hormones such as
cortisol and the catecholamines. The individual whose immune system is
impaired is more sensitive to the effect of stressful stimuli and is
more vulnerable to disease. The opposite is also true. For example,
women who suffer from breast cancer respond better to therapies and
exhibit a higher life expectancy correlated with an increase in immune
defenses, if they are more optimistic about their own recovery, trust
their doctors more, and believe that a complete remission is possible
(Wein, 2000). Stress, whether brought about by an acute or chronic event
or continuously maintained, can negatively affect various organs of the
human body: an increase in heart beat and blood pressure, disturbances
of the gastrointestinal apparatus, perspiration, tension and often pain
of the muscular fascia, genital problems (erectile dysfunction or
absence of one or more menstrual cycles). The psychological effects of
stress manifest themselves in nervousness, agitation, anxiety,
depression, sleep disturbances, difficulty in maintaining concentration,
and many more.
The mechanisms through which somatopsychic stress is converted into
psychosomatic disease are multiple and new connection between stress and
diseases such asthma and rheumatoid arthritis and many others are
continually established by research (Segerstrom & Miller, 2004). For
example, recent discoveries show that the levels of glycocorticoids,
typical hormones released in presence of stress, when chronically
elevated can become neurotoxins capable of damaging cells in rapid
multiplication in the region of the hippocampus, which is an important
center for memory processes (Lupien & Gillin, 1999; Scoville & Milner,
2000). Research has also shown that all phenomena characteristic of
somatopsychic decline, characteristic of the aging process, may be
accelerated by stress (McEwen, 1998).
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