Kelsey Graham by Kelsey Graham

You’ve likely experienced the physiological effects of stress—sweaty palms, racing heart, shallow breathing—and are familiar with the feeling of being overwhelmed it can bring. The stress response is part of the “fight or flight” mechanism that has helped our species thrive. However, the demands of modern life make this adaptive response problematic for our long-term well-being.

This article will cover the physiological underpinnings of stress, its impact on various bodily systems and useful strategies for navigating it.

The Physiology of Stress

The body’s stress response is governed by the sympathetic nervous system. When faced with acute danger, your body responds with a cascade of physical and hormonal changes that prepare you to respond. Some of these changes include:

  • Increased blood pressure and heart rate
  • A surge of the hormones epinephrine, norepinephrine and cortisol
  • Reduced blood flow to visceral organs and increased blood flow to musculoskeletal system
  • Heightened muscle tension
  • Inhibition of immunity, digestion and reproductive functions (Sapolsky, 1994)

When confronting immediate, life-threatening danger, these physiological responses are protective. They help mobilize the body’s available resources to increase the chance for survival. Anything not immediately necessary, such as growth, digestion and reproduction, gets downregulated. Unfortunately, when the perceived threat is no longer acute, but stems from constant daily pressures, these responses can threaten your well-being. Eventually, the body’s stress response may wreak more havoc than the stressor itself, impacting numerous health outcomes (American Psychological Association, 2019).

Chronic Stress and Weight

There is a strong correlation between high-stress levels and increased weight (Harding et al., 2014; Block et al., 2009). A variety of factors underlie this relationship. While some of the hormones associated with the stress response inhibit hunger, others increase it. Cortisol typically spikes in the latter parts of the stress response and stays elevated during the recovery phase. This hormone increases hunger and motivation to eat as a means of replenishing calories that might have been lost while responding to a stressor. The body’s stress response also increases the drive for hyperpalatable foods, such as quick-digesting carbohydrates and those that are high in fat, as a means of rapidly replenishing energy stores (Yau and Potenza, 2013).

In addition, cortisol spurs an increase in fat storage, particularly around the midsection. The fat cells located in the abdomen, known as visceral fat, are particularly sensitive to cortisol and store more fat than other areas when exposed to it. 

Chronic Stress and Digestive Function

Digestion is rapidly inhibited during stress. Blood flow is diverted away from digestive organs, gastrointestinal enzymes responsible for breaking down food decrease and peristalsis (the muscular contractions of the intestines that help move food along) is inhibited. When facing a critical threat, this is beneficial. Digestion is not immediately necessary and blood flow is redistributed to other working tissues. When stress becomes chronic, however, this weakens the digestive system. Stress can also increase markers of gastrointestinal inflammation and is related to conditions such as irritable bowel syndrome, ulcers, Crohn’s disease and ulcerative colitis (Yaribeygi et al., 2017).

Chronic Stress and Mental Health

Chronic stress can negatively impact mood, and high levels of stress are related to increased rates of both depression and anxiety (Khan and Alam Khan, 2017). Prolonged exposure to cortisol and other corticosteroids can increase feelings of anxiety and contribute to the development of depression. Elevated cortisol levels are often seen in individuals with major depression, and animals with high corticosteroid levels show symptoms of depression, such as poor sleep, locomotor changes, reduced appetite and low libido (Khan and Alam Khan, 2017). Additionally, individuals exposed to early life stressors are more likely to experience clinically significant mental health outcomes in adulthood (Schneiderman, Ironson and Siegel, 2005).

Chronic Stress and Disease

The prevailing theory behind lifestyle-related disease is that of underlying inflammation. Inflammation is part of the immune response to illness or injury, where white blood cells, antibodies and cytokines defend compromised tissues. Like stress, this is beneficial in the short-term. Chronic inflammation, however, promotes the development of most chronic diseases. Unchecked stress can incite or perpetuate systemic inflammation, and research reveals that stress is a common risk factor in 75-90% of modern diseases, including cardiovascular disease, diabetes, liver disease, Alzheimer’s and cancer (Liu, Wang and Jiang, 2017).

The Benefits of Stress

While it may seem that stress is inherently negative, it can be beneficial. Stress can boost cognition, motivation, memory, creativity, vigilance and perseverance. Furthermore, the way we perceive a stressor has a significant impact on how it affects us. Simply viewing a stressor as a “challenge” rather than a “threat” yields better physical and psychological consequences (Kilby and Sherman, 2016). Stress mindsets (our attitudes and beliefs about the effects of stress) alter our behavioral and psychological responses to threat, and thus, our long-term outcomes. Those who view stress as adaptive are less likely to be depressed, report higher levels of happiness and have greater life satisfaction than those who view stress as detrimental (McGonigal, 2015).

To objectively test the effect of mindset on the physiological stress response, researchers set up an experiment involving a mock interview and measured two stress hormones: cortisol and dehydroepiandrosterone (DHEA). As mentioned earlier, cortisol is behind some of the deleterious effects of chronic stress. It helps break down stored fuel and inhibit unnecessary systems during the stress response, but chronically high levels can hamper health. DHEA also rises during a stress response, which promotes brain growth, recovery and repair from stressors (McGonigal, 2015). Researchers randomly assigned participants to watch either a “stress is enhancing” or “stress is debilitating” video before their mock interviews. They found that, compared to the “stress is debilitating” group, those who watched the “stress is enhancing” video had a dramatically greater rise in DHEA, which is linked to improved health outcomes in response to stress (Crum et al., 2016).

Stress is a natural part of life. When unchecked, the body’s physiological response can negatively impact health. However, your mindset can transform your stress response, allowing it to enhance creativity, motivation and perseverance, ultimately helping you become more resilient in the face of future stressors. 

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