We all want to reduce the negative impact of stress from our daily lives, but we cannot do this without first a clear understanding of what is our stress, and when does it get unhelpful. So in this blog post, we will dive into the “taxonomy” of stress, and differentiate a potentially useful stress response from chronic stress, to later in our posts show how it diminishes our cognitive abilities and immunity.
Stress is a physiological response to an actual or anticipated threat that disrupts the organism’s internal balance, called the homeostasis (Morgado & Cerqueira, 2018). Stress triggers adaptive responses in our body by activating our autonomic nervous system through cortisol release in the hypothalamo-pituitary-adrenal axis to initiate the infamous “fight or flight” response. A natural response that aims to adapt the organism to the new set of conditions, stress is a very important tool for allostasis, defined by Sterling and Eyer, which is the body's natural way of maintaining internal balance (Sterling & Eyer, 1988).
Stress is influenced by experience, genetics, behavior and environment. Allostasis is the balance between the physiological responses and our adaptation to stressors. If there is an imbalance between Allostasis and Adaptation, then the Allostatic load can increase leading to chronic stress conditions (Figure from McEwen, 1998)
Allostatic load is a term that describes a deleterious situation when our body’s response to maintain this internal balance gets dysregulated either in its timing, variability or controllability (Juster et al., 2010; McEwen, 1998; Sousa, 2016; Sterling & Eyer, 1988). As a result, the body cannot recover from stress efficiently because stress response either accumulates excessively and/or appears repeatedly in an unhelpful way, or doesn’t get properly activated or deactivated (McEwen, 2007). Exposure to stressful conditions induces substantial changes in the system that manages this response, which can get damaged in long exposure to stress (Sousa, 2016).
Chronic stress is described by a prolonged elevation of stress. It shows itself in the body as sustained levels of increased heart rate and blood pressure, as well as the prolonged and higher levels of recorded sympathetic activity, such as higher levels of associated proteins and cells (McEwen, 2006). Its symptoms include feelings of fatigue, lack of energy, irritability, and demoralisation (McEwen, 2006). Chronic stress causes far reaching effects on our psychiatric, neurological and cardiovascular health and affects even our metabolism (Morgado & Cerqueira, 2018).
It has been noted that there are many individual differences, including maternal care, early life stress and genetics, that contribute to the stress responses we develop in adulthood (McEwen, 2006; Sousa, 2016) and there is a similar body of studies that show the versatility and individuality of the effects observed. Then, it is in the utmost interest of all of us to understand the different factors that contribute to switching our healthy stress response to chronic stress, and how chronic stress differentially affects us.
These two are goals we have set for ourselves at Sensae to deliver personalised care.