Embodying psychological thriving: physical thriving in response to stress - Thriving: Broadening the Paradigm Beyond Illness to Health

Toughening in rats is also related to the definitive health outcome: mortality. Daily exposure to mild stress increased rats' average life span by 18% (Frolkis, 1981). Thus, it appears that intermittent exposure to stressors that allows for time to recover before facing additional stressors may lead to resilience to future stressors. Similarly, when rat pups are exposed to handling or mild shock, their hormonal and behavioral responses to stress become much more resilient later in life, showing lower basal cortisol levels, quicker peak responses and recovery, stronger immunity, quicker physical development, fewer conflict-induced ulcers, less behavioral fear, and quicker avoidance learning (Gray, 1971; Levine, Haltmeyer, Karas, & Denenberg, 1967; Solomon & Amkraut, 1981). Finally, mild chronic stress administered before exposure to a carcinogen has been related to slower tumor growth (Monjan, 1981).

These studies have been used as an argument for exposing children to brief manageable stressors rather than oversheltering them. Clearly, some types of stressors, for limited durations, at specific developmental times, can be adaptive and transformative. This is in parallel to findings that stressors can enhance psychological resilience and competence (Garmezy, Masten, & Tellegen, 1984). Thus, exposure to manageable stressors can lead to physiological toughening - changes that decrease time spent in a catabolic state and boost immunity.

Adaptation to stressors as a form of toughening. Another example of toughening is increased speed of habituation to stressors. For example, we can examine changes in one's stress hormones over time in response to repeated exposures to the same stimuli. Lack of adaptation to stress, when individuals consistently react to familiar stressors, can cause intermittent stress to develop into chronic stress arousal. Although initial reactivity in response to novelty, uncontrollability, or perceived stress may reflect healthy functioning, repeated reactivity or nonhabituation to the same stimuli may over time lead to cortisol overexposure. In rats, severe stress can lead to nonhabituation or even sensitization of cortisol responses (Ottenweller et al., 1992; Pitman, Ottenweller, & Natelson, 1990). In humans, whereas cortisol usually habituates after the first exposure to repeated stressors (Gunnar, Connors, & Isensee, 1989; Levine, 1978; Mason, Brady, & Tolliver, 1968), certain individuals, such as hypertensives and men with negative psychological traits, can take longer to adapt (Al Absi & Lovallo, 1993; Kirschbaum et al., 1995).

In sum, quick adaptation to a familiar stressor may reflect physical thriving, reducing the amount of wear and tear on the body and increasing amount of time in restorative mode. Facile adaptation likely reflects psychological processes such as increased learning and psychological hardiness.

We speculate that when there is a manageable challenge, the anabolic component of the stress response increases. Few studies to date have examined this. In one study, Farrace and colleagues hypothesized that teachers of flying would experience training flights as a manageable challenge, whereas the student novice pilots would experience the training flights as a potential threat. After exposure to a training flight, the student pilots showed increased cordsol, growth hormone, and prolactin - a typical stress response - whereas the experienced teachers showed only an increase in growth hormone, but not of cortisol (Farrace, Biselli, Urbani, Ferlini, & De Angelis, 1996). As previously explained, high cortisol (with or without high growth hormone) is a high-cost catabolic stress response, whereas growth hormone alone, without the antagonistic effects of cortisol, should lead to growth and health (Panel A of Figure 2). Thus, for experienced pilots, we speculate that the manageable stressor of flying may be related to a positive profile of growth. Clearly, more research is needed to examine the clinical effects of a predominant cortisol versus growth hormone response to stress.