Page 117 - Biobehavioral Resilence to Stress

94 Biobehavioral Resilience to Stress

Normal
Physiological response
Stress

Activity
Recovery
Time
Allostatic load

Repeated "hits" Lack of adaptation
Physiological response

Normal response repeated over time
Time Normal adaptation
Time
Prolonged response Inadequate response
Physiological response No recovery

Time Time
Figure 5.2 Allostatic overload. Top panel shows a normal stress response that is
turned on by the stressor and shut off when the stressor is removed. The repetition
of many stressful events (upper left panel) and the lack of adaptation (upper right
panel) illustrate two types of chronicity leading to allostatic overload. Individual
stress responses may be prolonged (lower left panel) or inadequate to the situation
(lower right panel). When there is excess or insufficiency of one mediator (e.g.,
cortisol), other mediators are also affected (e.g., elevated infl ammation associated

with low cortisol; reduced inflammation associated with high cortisol). (From
McEwen, B.S., New Engl. J. Med., 338, 171–179, 1998. With permission.)

Allostatic overload is an essentially unhealthy outcome of chronic stress.
Initially, many predisease indicators are made worse by chronic stress. Such
indicators may include hypertension, obesity, metabolic alterations (e.g.,

elevated cholesterol and proinflammatory cytokines), loss of bone mineral

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