#Neurobiology of stress: #resilience and the adaptive nature of #allostasis in the human physiology, #StressInoculation

© Lisa Lukianoff 2014 copyright

An overview of the neurobiology of the stress response and early life experiences as an inoculation to stress in later life; a discussion about allostasis, resilience, and the HPA axis.

Inherent in our physiological blueprint are adaptive mechanisms designed to inoculate us against prolonged stress from becoming pathological. Our bodies coordinate complex biological responses in the peripheral and central nervous systems, involving the neuroendocrine and immune system, to protect against the potentially damaging effects of stress. Interestingly, many people do not develop anxiety and depression in response to stress  (Pfau & Russo, 2014).

Role of the hypothalamic-pituitary-adrenal (HPA) axis
During exposure to stress, the function of the hypothalamic-pituitary-adrenal (HPA) axis acts as a regulator, both influenced by and provide feedback to the hypothalamus, pituitary gland, and adrenal glands. The HPA function is a primary aspect of the neuroendocrine system in the stress response cycle, including bodily regulation of digestion, the immune system, emotions and moods, sexuality and the inflow and outflow of energy. It serves as a central mechanism for the complex interactions of hormones, glands, and parts of the general adaptation syndrome (GAS). The HPA axis combined with corticosteroids produces the physiological response to stress. (Lange C, Zschucke E, Ising M, Uhr M, Bermpohl F, Adli M., 2013).

Resilience and the adaptive nature of allostasis in the human physiology
Described in their research findings on the neurobiology of stress Pfau & Russo discuss the exceptional biological abilities and coping mechanisms involved in the process of resilience, (2104). They state that successful resilience response to stress involves allostasis, the body’s adaptive response and maintenance of a set-point. Maintaining a physiological homeostasis in response to stress is likely if the stressor ceases. Prolonged stress can produce a pathological stress response: depression and anxiety. This is the case with an allostatic load, producing a prolonged and potentially damaging biological response. 

Setting the stage for stress inoculation: early life experiences of moderate stress
Early life experiences of stressful events have been shown to attenuate the stress response and create a base for resilience and stress inoculation. Children who encounter early moderate stress have been shown to develop a “stealing” effect, a protective inoculation against future stress. These early experiences create a later in life stress resistance with overall enhanced psychological well-being and functioning, (Pfau & Russo, 2014, p. 67). However, allostatic loading, or too much severe stress exposure, can impair this protective feature. Prolonged or severe stress exposure can cause the hypothalamic–pituitary–adrenal (HPA) axis to over produce Glucocorticoids from the adrenal cortex; too many Glucocorticoids released can create structural changes in the brain and have a deleterious effect on cognition, emotion and behavior (Lupein, 2009). 

Exposure to moderate stress in early life and the experience of overcoming stressful events provides a foundation for future inoculation. 

“There is a rich literature on stress inoculation in rodents demonstrating that rats exposed to early life stress, including brief maternal separations and neonatal corticosterone administration, display blunted HPA axis response to stress in adulthood as well as behavioral resilience in the form of reduced anxiety-like behavior and enhanced performance in cognitive tasks…”, (Pfau & Russo, 2014, p. 67)

REFERENCES
Lange C, Zschucke E, Ising M, Uhr M, Bermpohl F, Adli M. (2013). Evidence for a normal HPA axis response to psychosocial stress in patients remitted from depression. Psychoneuroendocrinology. pii: S0306-4530(13)00250-3. doi:10.1016/j.psyneuen.2013.06.033. 

Pfau, M. L., & Russo, S. J. (2014). Peripheral and central mechanisms of stress resilience. Neurobiology of Stress. Volume 1; pp: 66-79. http://dx.doi.org/10.1016/j.ynstr.2014.09.004.