Overview
Allostasis is the active process through which the body anticipates changes and adjusts itself in an effort to maintain stability. As the body undergoes perceived changes in its environment, the brain constantly adjusts hormones, neurotransmitters, and signals throughout the nervous system. For instance, when exercising or physically working, the body raises its blood pressure to ensure it can keep up with the increased pace of activity.
When someone uses substances, the brain experiences a spike in dopamine and other neurotransmitters that are countered with chemicals like corticotropin-releasing factor (CRF) to protect oneself from overstimulation. In brief intermittent uses, this means the body eventually returns to a baseline, but chronic usage can permanently lower the baseline such that substances are used to alleviate a low mood rather than achieve a high mood. Allostasis describes the process through which these internal parameters are adjusted by the body in response to exposure from the environment, and the term “allostatic load” is used to describe the long-term effects on the body from these changes.
History and Etymologu
The origin of the concept of allostasis is closely tied to community-level health observations that found stressful events correlated heavily with chronic health issues developing later in life. While we might take this for granted, it was often thought prior to Peter Sterling and Joseph Eyer’s work that a reduced mortality rate when young would correlate with more chronic diseases later in life. Instead, Sterling and Eyer found that groups experiencing the most social disruption, such as unemployed Americans struggling with financial instability and African-Americans struggling with the interpersonal and systemic impacts of racism, were also the most likely to develop hypertension. Previously this was hypothesized to be a result of genetic predisposition, but Sterling and Eyer countered with a mind-brain-body model that connected external stressors to internal physiological changes and long-term health consequences. The model of homeostasis didn’t explain why blood pressure didn’t return to a normal state after fluctuations throughout the day and instead responded primarily to the presence or absence of stressors. Chronic stress could also lead to long-term changes in blood pressure, suggesting a form of adaptation and self-regulation that the idea of a steady baseline the body seeks a return to can’t explain. The cumulative damage incurred by a body under chronic stress is often called an “allostatic load.”