Allostasis & Allostatic Overload in Today's Society

     "The brain is the key organ of resilience because it governs allostatic systems that affect the entire body & also responds to those signals by showing adaptive plasticity. However, dysregulation of those same systems & their overuse can also lead to cumulative damage. We have summarized findings showing that circadian rhythms, governed by the master clock in the suprachiasmatic nucleus & synchronized by light-dark cycles &, in some peripheral cells, by circulating glucocorticoids are an important component of these responses, in that intact rhythms are necessary for efficient regulation of the stress axis, as well as other aspects of systemic physiology. We have reviewed evidence that shows that disrupted rhythms cause changes in neural structure in humans & non-human animals, decrease cognitive flexibility, and dysregulate metabolic systems. Other consequences of circadian disruption need to be explored in view of the widespread occurrence of circadian disruption in modern society, including urban life, shift work & jet lag.
     The goal of this review was to overview the factors that can confer resilience or mediate susceptibility not just at the level of an individual but also at the level of cells & neural circuits, since the brain is the master organ of stress & adaptation, and determines whether adaptation will be successful (allostasis) or lead to pathophysiology (allostatic overload).  
     In the context of the rapid development of modern human society over the past 100 years, these evolutionarily ancient systems have not yet ‘caught up’. In a sense, we are asking too much of our physiology, in that allostatic systems that played a key role in survival when resources were scarce or were activated when the individual was threatened by predators are now engaged with worry, social conflict & overwork. In developed societies, this all occurs in an environment of ample metabolic resources in the form of fast food or other high calorie consumables but with less & less physical activity. Coupled with an always-on-the-go society, where the sleep-wake cycle has been almost completely separated from the solar day & electric lighting & electronic gadgets provide us with ample light long into the night, there is no doubt that many of us live in a state of high allostatic load or even overload. The physical & mental health costs of this lifestyle are only now being appreciated, in the form of rampant obesity, increased cardiovascular disease & a rise in psychiatric disorders. By more clearly delineating the different players in this complex web, from the molec- ular & cellular through to the organismal & even societal levels, we will perhaps be able to tackle more easily some of these issues by finding ways to mitigate their effects, increase the resilience of individuals to such insults or, even better, prevent them from happening in the first place."

       Karatsoreos IN, McEwen BS. Psychobiological allostasis: resistance, resilience and vulnerability. Trends Cogn Sci 2011; 15(12): 576-84.

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