Page 183 - Biobehavioral Resilence to Stress

160 Biobehavioral Resilience to Stress

Stress-induced changes in immune function have been well-described in
animal models (Glaser & Kiecolt-Glaser, 2005; Kapcala, Chautard & Eskay,
1995) and in human subjects (Cohen et al., 1991). However, some forms of

stress may not have any near-term effect on immune function. For example,

there appears to be no effect of prolonged aerobic exercise on immune func-
tion and susceptibility to disease (Nieman, 2000). Perceptions, attitudes, and

attention to stress may play an important role. The near-term effects of envi-
ronmental stress on immune function are apparently sensitive to psychologi-
cal stress (Friedl, 2003). When introduced gradually or imperceptibly, some
stressors (e.g., heat, hunger) fail to activate any stress-related HPA responses

(Mason, 1975). This suggests that perception and neuropsychological pro-
cessing play a fundamental role in responding to stress, and that accommo-
dation to gradual or continuous stress (allostasis; McEwen, 1998, 2005) can
occur without negative health consequences.
Perceived threat is an important determinant in physical responsiveness
to stress, particularly when confronted with novel situations or events. Initial
experiences with public speaking evoke measurable stress-related responses
(e.g., increases in salivary cortisol), but this response is greatly reduced by
repeated exposure (Kirschbaum et al., 1995). Personality variables may also
play a role. For some individuals, repeated exposure had no eff ect on stress
response as measured by salivary cortisol. Kirschbaum et al. (1995) were
able to identify this subgroup of “high responders” as persons with low self-
esteem. Apparently, the task of public speaking remained highly stressful for

these individuals, even after repeated exposure. Thus, it may be important to

consider key personality traits as possible variables of influence on respon-

siveness to specifi c stressors.

Psychoneuroimmunology is an emerging interdisciplinary field of study
that accesses contributions from psychology, neurology, endocrinology, and
immunology to explore relationships between stress, psychological (“men-
tal”) outlook, and illness. Findings from studies in this area have a wide
impact upon our understanding of the complexities of the brain and behavior,
the immune system, and physical health. Most research to date has focused
on the question of how physical and psychological stressors aff ect immune
system functions, and how these effects in turn affect physical health. Two

leading psychoneuroimmunologists have developed a sophisticated model to
represent the interplay between the human central nervous system (CNS)
and immune and endocrine systems (see review by Glaser & Kiecolt- Glaser,
2005). Critical to this model is the notion of bidirectional infl uence. For
example, stress-related hormones directly or indirectly (via modulation of
cytokines) affect the functioning of T and B cells, neutrophils, macrophages,

and other cellular entities (Padgett & Glaser, 2003). In return, cytokines can
aff ect the CNS by actions on the hypothalamic production of stress-related
hormones (Figure 7.4).

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