I will never forget the day I received the call that I was accepted to UC Davis School of Veterinary Medicine. I started crying so loudly that the lady on the other end of the line asked if I was OK. I was only able to choke out a “thank you” in response.
When the first day of school arrived, I met 147 other students who I could tell all felt the same way. Many of us had dreamed of this day from the time we went on our first school trip to the zoo or adopted our first family pet. But after two weeks of orientation, when classes finally began, reality set in.
Now that I was here, I didn’t know if I was equipped to deliver what was expected of me in order to succeed in this new environment—expectations I largely put on myself. New challenges, new school, new city—was this my new identity? I wanted to run.
So that’s exactly what I did. On the treadmill, on the track, around my neighborhood, anywhere. As it turns out, that’s what I’ve been doing ever since. Having experienced firsthand the benefits of exercise in adapting to stressful situations and maintaining overall health, I want to share with my veterinary student colleagues so they can realize these same benefits for their own mental and physical health.
How stress is bad for the brain
According to the National Institute of Mental Health, stress is “the brain’s response to any demand.” It’s important to note that not all stress is bad. The stress response is mediated by the sympathetic nervous system and has evolved to accentuate utility, shuttling our resources to only the most vital organs needed to help us escape from the perceived threat.
As our environment has changed, though, so have its demands. The need to hunt or risk starvation has been replaced by the need to drive to the local market—but the stress response has remained the same. When we feel as though a demand can’t be met or our desires can’t be satisfied, our stress response turns from useful to debilitating. Chronic stimulation of the body’s survival mechanism can lead to mental health disorders and other detrimental effects.
In short, chronic stress is bad for the brain. The stress response is a complex cascade of events involving the stimulation and response of many brain structures, ultimately leading to the release of hormones that elicit physical changes such as increased breathing or heart rate. An important component of the stress response is activation of the HPA axis, a complex system composed of the hypothalamus, pituitary gland and adrenal glands.
In response to a stressor, the hypothalamus releases corticotropin-releasing hormone (CRH) and vasopressin, activating the HPA axis and resulting in the secretion of glucocorticoids—namely cortisol. With repeated exposure to stressors, prolonged HPA axis activation will drive elevated levels of cortisol in the body along with its catabolic effects.
While a normal glucocorticoid level can facilitate neurogenesis by supporting neuronal connections, an abnormally high level resulting from chronic stress will produce effects in our neuronal synapses linked to the onset of depression. Glucocorticoid resistance can lead to chronic activation of the inflammatory response,1 which has been associated with such symptoms as fatigue and sleep impairment,2,3 along with loss of sociability, poor memory and impaired cognitive capability.4 These are only a few of the neurobiological connections between chronic stress and psychiatric disorders.
How exercise is good for the brain
This is where exercise comes in! Physical activity helps offset the buildup of stress while also acting as a mood-enhancing agent. Exercise puts stress on the body by activating the sympathetic nervous system and inducing glucocorticoid secretion. Sounds familiar, right? The difference is that this stress response is acute—it involves a brief elevation of glucocorticoid levels followed by a swift return to physiologic levels. In fact, physically active individuals have a notably altered tissue sensitivity to glucocorticoid secretion.
In one study, rats given voluntary access to cardio for four weeks showed an attenuated glucocorticoid response to psychologically stressful stimuli when compared with the non-exercise group—a response that corresponded to less anxious behavior.5 As veterinarians, having the ability to maintain hormonal balance during a stressful event could be the key to maintaining our composure and efficacy in the face of a clinical emergency.
Exercise can also be used as a tool to build mental toughness. In a study that assessed more than 100 healthy men and women, those who exercised regularly showed less of a decline in positivity after exposure to an acute psychosocial stressor than sedentary individuals.6 Exercisers also scored higher on measures of friendliness after completing stressful tasks. And subjects who exercised regularly were able to maintain greater positive mood during and after the exposure to stress than those who did not. This ability to recover quickly from adversity is often termed “resilience.”
Since exercise is a stressor itself, it’s possible that it helps us adapt over time to respond to stressful events more efficiently. This “crossed-stressor adaptation hypothesis” explains how adaptation to exercised-induced stress may modify our physiological response to stressors that don’t involve exercise.7 In a vet school context, studying helps us learn information, and exercising may help us recollect that information in the more pressing situations we’ll encounter as care providers.
How stress is bad for the body
Stress is bad for our bodies too—not the kind of stress we put on ourselves by running a 5k but the kind associated with worrying about remembering the steps in the dorsal column medial lemniscus pathway or the anatomic location of beta-2 adrenergic receptors. Have you ever gotten sick before or directly after a stressful event? This is a physical response to chronic stress. Mind and body are entities that operate in coordination with one another—what affects mind also affects body.
As it turns out, the rise in cortisol resulting from HPA axis activation that affects our neuronal synapses also affects our immune system. While cortisol reduces inflammation in the body when it’s released acutely, it has the opposite effect when it reaches levels too high for the body to respond to appropriately. Sustained HPA axis activation and glucocorticoid resistance cause an increase in proinflammatory cytokines, leading to inflammation.
The duration of stress has been shown to be proportional to the severity of immune system damage. Inflammation leads to a heightened risk for developing cancer, cardiovascular disease and diabetes. More directly, chronic stress can lead to increased expression of genes that induce cell death, leading to apoptosis of lymphocytes and an overall decrease in the total number of these cells in the body.8 This depletes us of the armor we need to fight off the enemy surrounding us during cold and flu season.
How exercise is good for the body
Unlike the chronic stress we feel when we’re approaching finals or preparing for our first week of clinics, stress from exercise can be turned on and off to allow prolonged periods of rest and recovery. One study of lab animals showed that acute stress is immunoenhancing, as demonstrated by the results of a delayed-type hypersensitivity (DTH) test to assess cell-mediated immune response. Increasing the intensity of the acute stress led to an even greater increase in DTH response.9
These results suggest that exercise may help the body mount a response to antigen that’s quicker and greater in magnitude than it would be without exercise. Exercise as an acute form of stress can boost immune system function and therefore make a huge difference in students under conditions of prolonged stress.
Why this is important for vet students
A study performed by Merck Animal Health this year found that veterinarians align with the general population in mental illness statistics but are below average in maintaining adequate well-being.10 The study defines mental health as “psychological distress” and well-being as “the way individuals think and feel about their lives compared to the best/worst possible lives they can imagine.” The study also found that many of those who are suffering from psychological distress are not receiving treatment.
As is true of any community, each veterinary school has its own distinct culture. I can only speak about my own experience as a first-year veterinary student at UC Davis when I share how the conversation about mental health and well-being has always been very transparent and even encouraged. Faculty members have been immensely brave in opening up about their personal hardships, inspiring peers in my class to do the same.
Before applying to veterinary school, I had never heard of “compassion fatigue” or “imposter syndrome.” But sensitive topics such as these were discussed within our first week of orientation. And during our first semester, Barry Kipperman, DVM, DACVIM, led an ethics course that explained veterinarians’ role as advocates for beings that cannot advocate for themselves. I began to see why so many veterinarians are consumed by this responsibility and how easily one can feel unable to meet this demand—cue the stress response!
Recommendations made by Merck at the end of its study include setting healthy expectations for work-life balance. James Clark, DVM, MBA, a teacher and mentor to veterinary students at UC Davis as well as a multi-practice owner, focuses on practical steps we can take to address the mental health challenges we may face in our careers, or even now as students. He has instituted a “21-day challenge” whereby students do one thing every day for 21 days that they believe will make them more happy and productive. His goal is to help us establish “healthy habits that persist.” I chose to fit at least 20 minutes of sweat into my day every day, and over half the class decided to set similar goals.
Dr. Clark has put forth this challenge to each UC Davis vet school class for the past five years, and he told us that more than half the class has chosen to participate every year. This commitment to wellness is truly inspiring and gives me hope that I’m witnessing a shift in our profession toward greater self-care.
As veterinary students, we’re challenged every day to be adaptable and to be problem-solvers. We’re confronted with cases involving species we didn’t even know existed let alone know how to treat. I echo many of my colleagues when I say we’re overwhelmed by the knowledge we don’t yet possess and may not have the time to learn in these four short years. But rather than feeling burdened by this responsibility, I often consider how we may benefit from it. How can we respond to stressors in a way that’s productive and conducive to our growth as professionals? While exercise may not be the only answer, I’m convinced that it’s a start.
Exercise has allowed me to view stressors in my life in a similar way to how I view the beginning of my workouts. When I start my run, I worry that I won’t be able to finish or that I’ll fatigue quickly. But as I keep putting one foot in front of the other, I know that I’m closer to finishing, and I don’t worry about how many paces I have left because I’m constantly progressing. I try to use this as a model for my four years as a veterinary student. And hopefully once I begin my career, I won’t be envisioning the finish line anymore because I’ll be consumed by the satisfaction of moving forward—one foot in front of the other.
1. Silverman MN, Sternberg EM. Glucocorticoid regulation of inflammation and its functional correlates: From HPA axis to glucocorticoid receptor dysfunction. Ann N Y Acad Sci 2012;1261(1):55-63.
2. Meyers CA, Albitar M, Estey E. Cognitive impairment, fatigue, and cytokine levels in patients with acute myelogenous leukemia or myelodysplastic syndrome. Cancer 2005;104:788-793.
3. Motivala SJ, Sarfatti A, Olmos L, et al. Inflammatory markers and sleep disturbance in major depression. Psychosom Med 2005;67:187-194.
4. van der Kooij MA, Fantin M, Rejmak E, et al. Role for MMP-9 in stress-induced downregulation of nectin-3 in hippocampal CA1 and associated behavioural alterations. Nature Comm 2014;5:4995.
5. Droste SK, Chandramohan Y, Reul JM. Voluntary exercise impacts on the rat hypothalamic-pituitary-adrenal axis mainly at the adrenal level. Neuroendocrinol 2007;86:26-37.
6. Childs E, Wit HD. Regular exercise is associated with emotional resilience to acute stress in healthy adults. Front Physiol 2014;5:161.
7. Sothmann MS, Buckworth J, Claytor RP, et al. Exercise training and the cross-stressor adaptation hypothesis. Exerc Sport Sci Rev 1996;24:267-287.
8. Sarjan H, Yajurvedi H. Chronic stress induced duration dependent alterations in immune system and their reversibility in rats. Immunol Let 2018;197:31-43.
9. Dhabhar FS, Mcewen BS. Acute stress enhances while chronic stress suppresses cell-mediated immunity in vivo: A potential role for leukocyte trafficking. Brain Behav Immun 1997;11(4):286-306.
10. Study compares mental health and well being of veterinarians and general population. Merck Veterinary Manual, March 13, 2018. Available at: www.merckvetmanual.com/news/editorial/2018/03/13/17/45/study-compares-mental-health-and-well-being-of-veterinarians-and-general-population.