Psychosocial Topics

 What is the fundamental process through which organisms actively adjust to both predictable and unpredictable life events? (McEwen & Wingfielf, 2003) Allostasis, is a concept proposed more than 30 years ago, but its precise meaning and practical application remain elusive (Schulkin & Sterling, 2019). Allostasis simply put is “stability through change” and occurs when there is a challenge to homeostasis; these kinds of stressors can produce what is called an “allostatic load” that will generate an allostatic state and eventually can lead to a disease state (Koob & Schulkin, 2019).  When adaptive systems are triggered on and off again, but not too frequently, the body can easily cope through allostasis (McEwen, 1998). However, even though stressors promote adaptation, prolonged stress can lead to the breakdown of the body (McEwen, 2004). Those systems can be overstimulated or dysfunctional, and that condition, the "allostatic load" becomes the price for adaptation (McEwen, 1998). 

There are 3 types of allostatic load: quick, repeated activation of allostatic systems, failure to shut off allostatic activity after stress response, and inadequate response of allostatic systems that leads to elevated activity of normally counter-regulated allostatic systems after stress (McEwen, 1998). Allostatic load is those cumulative effects of the stress of daily life and when the cost of chronic exposure to heightened systemic physiologic responses exceeds the coping mechanisms of an organism and allostatic overload ensues (Fava et al., 2019). Resultantly, allostatic load can impair immunity. It can also cause atherosclerosis, obesity, bone demineralization, and atrophy of brain nerve cells. Many of these processes are part of major depressive illnesses and chronic anxiety disorders (McEwen, 2004). Allostatic load also refers to the cumulative cost to the body of allostasis, and allostatic overload is the state to which more serious pathophysiology can occur (McEwen & Wingfielf, 2003). 

There are two kinds of allostatic overload. One, is when energy demand exceeds supply. Entering into a survival mode decreases this type of allostatic load and regains positive energy balance so normal life can be resumed (McEwen & Wingfielf, 2003). Two, is when there is sufficient energy consumption accompanied by social conflict and other types of social dysfunction. This is the type affecting human society. In all cases, secretion of glucocorticosteroids, the autonomic nervous system, CNS neurotransmitters, and inflammatory cytokines act as activity mediators of allostasis as they wax and wane with allostatic load (McEwen & Wingfielf, 2003). If allostatic load is continually high, then pathologies occur. Type 2 allostatic overload can only be counteracted through education and changing social structure.

The brain is the organ of adaptation to experiences, and that includes stress (McEwen, 2016). Stress can change the brain’s architecture and alter systemic function through neuroendocrine, autonomic, immune, and metabolic systems. The brain is the master regulator of these systems, and behavior, so by altering brain function through chronic stress can have both direct and indirect effects on allostatic overload and the cost of adaptation.  The healthy brain has a large capacity for resilience, and ability to respond with plasticity toward better health. Plasticity-facilitating treatments could be the framework of a positive behavioral intervention for allostatic overload (McEwen, 2016).

References

Fava, G. A., McEwen, B. S., Guidi, J., Gostoli, S., Offidani, E., & Sonino, N. (2019). Clinical characterization of allostatic overload. Psychoneuroendocrinology, 108, 94–101. https://doi.org/10.1016/j.psyneuen.2019.05.028

Koob, G. F., & Schulkin, J. (2019). Addiction and stress: An allostatic view. Neuroscience & Biobehavioral Reviews, 106, 245-262. doi:10.1016/j.neubiorev.2018.09.008. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/30227143/

McEwen, B. S. (1998). Stress, Adaptation, and Disease: Allostasis and Allostatic Load. Annals of the New York Academy of Sciences, 840, 33-44. doi:10.1111/j.1749-6632.1998.tb09546.x. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/9629234/ 

McEwen, B. S. (2004). Protection and damage from acute and chronic stress: Allostasis and allostatic overload and relevance to the pathophysiology of psychiatric disorders. Annals of the New York Academy of Sciences, 1032, 1–7. https://doi.org/10.1196/annals.1314.001

McEwen, B. S. (2016). In pursuit of resilience: Stress, epigenetics, and brain plasticity. Annals of the New York Academy of Sciences, 1373(1), 56–64. https://doi.org/10.1111/nyas.13020

McEwen, B. S., & Wingfield, J. C. (2003). The concept of allostasis in biology and biomedicine. Hormones and Behavior, 43(1), 2–15. https://doi.org/10.1016/s0018-506x(02)00024-7

Schulkin, J., & Sterling, P. (2019). Allostasis: A Brain-Centered, Predictive Mode of Physiological Regulation. Trends in Neurosciences, 42(10), 740-752. doi:10.1016/j.tins.2019.07.010. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/31488322/