Over the coming months, I'm going to be writing a series on the basics of health neuroscience for the Pittsburgh Post Gazette Wellness section, found here. First post is up!
We all know that stress is bad for us. Stress-related chronic diseases impact an enormous amount of people; it is estimated that 70% of deaths in the United States each year are from chronic diseases (1), and two-thirds of Americans now believe that their stress has a moderate or strong impact on their physical health (2). We now know that chronic stress also affects the physical structure as well as the function of your brain.
Stress affects the size and thickness of a few different regions of your brain – the one we'll focus on here is the amygdala, an almond-shaped structure located deep within your brain.
|(Amygdala in cross-section)|
During acute stressors, the amygdala helps orchestrate the brain’s rapid fight or flight response (3). This response can be adaptive in some settings, but repeated, excessive, or prolonged stress responses are thought to place people at risk for stress-related diseases (4,5). The amygdala has been shown to be a key player in mental and emotional health, with abnormal amygdala function identified in depression, anxiety, posttraumatic stress disorder, phobias, and panic disorders (6–8). Higher levels of perceived stress in a large sample of community adults have been associated with increased size of the amygdala (9). Moreover, some recent work suggests that reductions in perceived stress are associated with reduced amygdala density (10).
Under stress, specific functional neural changes have been observed in amygdala to prefrontal cortex (a higher order "thinking" area) circuitry, with the amygdala activating stress pathways that result in impaired prefrontal functions such as attention and working memory (3). Essentially, stress is changing how different brain regions "talk" to each other. This occurs even when your brain is at rest – it is reflected in baseline patterns of brain activity, where changes in neural functional connectivity have been shown between the amygdala and frontal brain regions in people with stress-related disorders (11–13).
The good news is that your brain is remarkably plastic – that is, it continues to change, structurally and functionally, in response to your environment and actions. So…next up: what you can do to protect your brain against the effects of chronic stress.
1. Kung H-C, Hoyert DL, Xu J, Murphy SL. Deaths: final data for 2005. Natl Vital Stat Rep Cent Dis Control Prev Natl Cent Health Stat Natl Vital Stat Syst. 2008 Apr 24;56(10):1–120.
2. The Impact of Stress: 2012 [Internet]. http://www.apa.org. [cited 2013 Oct 30]. Available from: http://www.apa.org/news/press/releases/stress/2012/impact.aspx
3. Arnsten AFT. Stress signalling pathways that impair prefrontal cortex structure and function. Nat Rev Neurosci. 2009;10(6):410–22.
4. Gianaros PJ, Sheu LK, Matthews KA, Jennings JR, Manuck SB, Hariri AR. Individual Differences in Stressor-Evoked Blood Pressure Reactivity Vary with Activation, Volume, and Functional Connectivity of the Amygdala. J Neurosci. 2008 Jan 23;28(4):990–9.
5. McEwen BS. Seminars in Medicine of the Beth Israel Deaconess Medical Center: Protective and damaging effects of stress mediators. N Engl J Med. 1998;
6. Siegle GJ, Thompson W, Carter CS, Steinhauer SR, Thase ME. Increased Amygdala and Decreased Dorsolateral Prefrontal BOLD Responses in Unipolar Depression: Related and Independent Features. Biol Psychiatry. 2007 Jan;61(2):198–209.
7. Kiehl KA, Smith AM, Hare RD, Mendrek A, Forster BB, Brink J, et al. Limbic abnormalities in affective processing by criminal psychopaths as revealed by functional magnetic resonance imaging. Biol Psychiatry. 2001 Nov 1;50(9):677–84.
8. Mervaala E, Föhr J, Könönen M, Valkonen-Korhonen M, Vainio P, Partanen K, et al. Quantitative MRI of the hippocampus and amygdala in severe depression. Psychol Med. 2000 Jan;30(1):117–25.
9. Taren AA, Creswell JD, Gianaros PJ. Dispositional Mindfulness Co-Varies with Smaller Amygdala and Caudate Volumes in Community Adults. PLoS ONE. 2013 May 22;8(5):e64574.
10. Hölzel BK, Carmody J, Evans KC, Hoge EA, Dusek JA, Morgan L, et al. Stress reduction correlates with structural changes in the amygdala. Soc Cogn Affect Neurosci. 2010 Mar;5(1):11–7.
11. Etkin A, Prater KE, Schatzberg AF, Menon V, Greicius MD. DIsrupted amygdalar subregion functional connectivity and evidence of a compensatory network in generalized anxiety disorder. Arch Gen Psychiatry. 2009 Dec 1;66(12):1361–72.
12. Lanius RA, Bluhm RL, Coupland NJ, Hegadoren KM, Rowe B, Théberge J, et al. Default mode network connectivity as a predictor of post-traumatic stress disorder symptom severity in acutely traumatized subjects. Acta Psychiatr Scand. 2010;121(1):33–40.
13. Bluhm RL, Williamson PC, Osuch EA, Frewen PA, Stevens TK, Boksman K, et al. Alterations in default network connectivity in posttraumatic stress disorder related to early-life trauma. J Psychiatry Neurosci JPN. 2009 May;34(3):187–94.