20 Jun How Chronic Stress Can Shrink Your Brain
By Maya Inaltong
The human body is constantly reacting to stressors, whether internal or from the environment. Temporary stressors can activate healthy responses in the body, but consistent and long-term sources of stress can be damaging.
When a stressor is detected, information about it is sent to the amygdala, the region of the brain that deciphers images and sounds. If there seems to be danger, the amygdala sends a signal to the hypothalamus, a part of the brain that controls homeostasis by regulating body temperature, heart rate, and mood. The hypothalamus proceeds to take over the body and activate the sympathetic nervous system (SNS). The first step in this activation process is the release of the hormone norepinephrine and epinephrine (adrenaline) throughout the bloodstream. These hormones trigger a quicker heart rate, faster breathing, and higher blood pressure, allowing us to respond quickly to threats and stressful situations with enough energy. Once the initial response of the hormones diminishes, the hypothalamus activates the secondary stress response system: the hypothalamic-pituitary-adrenal axis (HPA axis). The HPA axis allows the body to stay on alert for longer periods of time by permitting the release of cortisol, a hormone that helps regulate the body’s response to stress.
Stress in moderate amounts is healthy for us, but our brains can undergo many detrimental changes if exposed to severe chronic stress for long periods of time. When the SNS and HPA axis are constantly activated, the body produces elevated levels of cortisol, which have been associated with reduced volume of neurons and circuits in the hippocampus, amygdala, and prefrontal cortex, which are all integral parts of emotional regulation, decision making, and storing memories. Additionally, when the amygdala is constantly exposed to cortisol, it becomes hyperactive towards fear stimuli and activates the SNS system for much smaller threats, like triggering sounds or emotions.
So the stress caused by a looming deadline or important exam might be natural and healthy, but the constant anxiety that arises out of being in a toxic relationship or living in a violent household may negatively impact you in ways that are detrimental to your long-term health.
Ehrenfeld, T. (2018, December 7). The Three Types of Stress. Psychology Today. https://www.psychologytoday.com/us/blog/open-gently/201812/the-three-types-stress?scrlybrkr=b69b7d80
Harvard Health Publishing. (2022, July 6). Understanding the stress response.″ Wiktionary. https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response?scrlybrkr=b69b7d80
Hypothalamus. (2021, April 24). MedlinePlus.
Lupien, S. J., Juster, R.-P., Raymond, C., & Marin, M.-F. (2018, February 5). The effects of chronic stress on the human brain: From neurotoxicity, to vulnerability, to opportunity. PubMed. https://pubmed.ncbi.nlm.nih.gov/29421159/
Thau, L., Gandhi, J., & Sharma, S. (n.d.). Physiology, Cortisol – StatPearls. NCBI. https://www.ncbi.nlm.nih.gov/books/NBK538239/
Echouffo-Tcheugui, J. B. (2018, August 10). Circulating cortisol and cognitive and structural brain measures: The Framingham Heart Study. NCBI. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6260201/
Hormonal Regulation of Stress | Biology for Majors II. (n.d.). Lumen Learning. https://courses.lumenlearning.com/wm-biology2/chapter/hormonal-regulation-of-stress/
Kluth, L. (2023). Stress and the Brain Illustration.