The stress response system is a life-saving adaptation that's allowed humans and mammals to survive and thrive throughout time. Whether it was running from a predator during the caveman days or hustling to meet a work deadline in present-day, the body's response to these external situations is designed to help us succeed.
While this system is effective for short bursts of time, or "acute stress," problems arise when we are chronically stressed or worried. "Chronic stress" continually triggers the body's stress response, keeping us in fight-or-flight mode longer than the system is designed to support.
The link between high levels of stress and negative health outcomes is well established, which is why it's important to be aware of your stress levels and how to manage them. Before discussing the signs of an altered stress response, we will do an overview of the hormonal and physiological changes that make up the stress response mechanism.
What happens during the stress response
Stress response begins in the brain. When a threat is present, the eyes and ears send sensory information to the amygdala, a part of the brain responsible for emotional processing. The amygdala analyzes this information and, during a stressful event, sends a distress signal to the hypothalamus, or the "command center" of the brain .
The hypothalamus is critical as it controls the autonomic nervous system (ANS), which is responsible for "automatic" bodily functions that we don't have to think about (e.g., breathing, heart rate, constriction/dilation of blood vessels).
The ANS has two parts: the sympathetic nervous system and parasympathetic nervous system. The sympathetic triggers the "fight or flight" response while the parasympathetic signals to "rest and digest".
When the hypothalamus receives the distress signal from the amygdala, it activates the sympathetic nervous system. This results in action from both the adrenal glands and HPA axis.
These small glands on top of the kidneys respond by releasing the hormone epinephrine into the bloodstream. More commonly known as "adrenaline," this hormone causes the heartbeat to quicken to deliver extra blood to the heart, muscles, and organs. The increased heart rate leads to increased blood pressure.
Epinephrine also floods the bloodstream with energy (in the form of glucose and fats) so your muscles can have ample fuel ready to be used . After this, the second part of the stress response begins, mounted by the HPA axis.
The HPA axis is comprised of the hypothalamus, pituitary gland, and adrenal glands. It's responsible for sustaining the stress response if the brain continues to perceive a threat.
To start the hypothalamus releases corticotropin-releasing hormone (CRH), which signals the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH travels to the adrenal glands triggering the release of cortisol .
The stress response produces effects lasting for short periods of time. Elevated levels of epinephrine, cortisol, and blood sugar, coupled with an increased heart rate and high blood pressure, have negative health consequences if continually present.
Signs your body is stressed
Signs that can indicate an altered stress responses include biomarkers like cortisol levels, using biofeedback tools, and observing lifestyle factors providing insight into how your body responds to stress.
The key biomarker for measuring stress is Cortisol, also known as the "stress hormone".
Cortisol is a glucocorticoid hormone, a type of steroid hormone, responsible for regulating your body’s stress response, suppressing inflammation, and regulating blood pressure and blood sugar. It also helps with the metabolism of nutrients and affects your sleep-wake cycle.
Almost every tissue in your body has a receptor for cortisol. It's important to check cortisol levels through either a salivary, blood, or urine test to gauge the body's stress levels
Cortisol peaks in the morning and then drops throughout the day, hitting its lowest point at midnight. Because of this, samples are typically taken in the morning. For a more comprehensive view, multiple samples are taken throughout the day.
Low cortisol levels (hypocortisolism) is considered adrenal insufficiency . This can be caused by an autoimmune condition (Addison's disease) or an under-active pituitary gland.
Weakness, fatigue, low appetite, weight loss, or low blood pressure can be physical symptoms of low cortisol production.
High cortisol is usually classified as Cushing's disease. It could also point to the presence of neuroendocrine tumors.
Weight gain, high blood pressure, high blood sugar (diabetes), excessive hair growth, or weak bones are physical symptoms of high cortisol .
Biofeedback is a non-invasive way to assess the physiological response and health of your body. Looking at heart rate variability (HRV), resting heart rate, and sleep quality can shed light on how your body handles stress.
One biofeedback measurement tool is HRV, or heart rate variability, the variance in time between each heartbeat. Ideally, the time between each beat should vary (e.g., 1.3 seconds between beats, followed by 0.9 seconds between beats). "The greater this variability is, the more ready your body is to execute at a high level" .
This relates to the parasympathetic and sympathetic branches of the autonomic nervous system. The sympathetic "fight or flight" activation will increase heart rate, while the parasympathetic "rest and digest" activation will slow heart rate, thus affecting HRV.
Although it may seem counterintuitive (because many assume both heart rate and HRV should be steady and consistent), HRV is supposed to fluctuate throughout the day as there should be times when you're relaxed and then times you're body is under stress, like when exercising.
High HRV means your heart is receptive to input from both sympathetic and parasympathetic branches of the nervous system. It indicates a balance between them.
Low HRV can indicate one side is dominant over the other, usually the sympathetic. This could be a sign your body is continually mounting a stress response; an increase in the sympathetic-to-parasympathetic ratio is being linked to increased cardiovascular morbidity and mortality .
Resting heart rate
Resting heart rate is how many times your heart beats per minute at rest. The healthy range is between 60-100 beats per minute. Very healthy individuals, like long-distance runners, can have a resting heart rate as low as 40.
Factors that affect resting heart rate include circulating hormone levels, physical fitness, and autonomic nervous system health.
In a stressful situation your heart rate might speed up. But by the end of it, it should return back to normal. An elevated heart rate for a prolonged amount of time is a sign your body may have an altered stress response.
Check your heart rate
Many health devices can be worn to monitor heart rate. It's also easy to check it yourself. Using your pointer finger and index finger, place them on the opposite wrist just below the base of the thumb or on the side of the neck just below the jawbone. You should be able to feel each beat; count the beats in 15 seconds, and then multiply by four to get your heart rate.
If you suspect you have an elevated heart rate, it's important to go to the doctor to rule out other health conditions.
It's no surprise that sleep quality and stress levels have an inverse relationship.
The sleep-stress cycle refers to the bidirectional relationship between sleep and stress: sleeping less increases stress levels the next day, and increased stress levels decrease sleep quality. It's a negative cycle that perpetuates the problem.
This is because sleep and stress share the same pathway: the HPA axis. Studies show that an overactive HPA axis is linked with decreased sleep quality and amount , and that the day after a rough night of sleep, your body produces higher amounts of cortisol.
In a sleep-stress study, The American Psychological Association found that "adults who sleep fewer than eight hours a night are more likely to report symptoms of stress in the past month". They also concluded that "adults with lower reported stress levels report sleeping more hours a night than do adults with higher reported stress levels" .
If you find yourself having a hard time falling asleep or staying asleep, it could be a sign of HPA axis dysregulation, meaning the body is not relaxed enough to enter a deep sleep state.
Lifestyle factors can also be signs of altered stress responses.
Low energy levels
Prolonged stress depletes daily energy levels. There are multiple ways it can affect energy throughout the day:
- High cortisol levels have been shown to inhibit function of the prefrontal cortex, the region of the brain responsible for executive functions (e.g., decision making, attention).
- A prolonged stress response can deplete nutrients needed to create energy, like B vitamins and magnesium.
- Chronic stress reduces levels of serotonin and dopamine, which help regulate mood, energy, and motivation.
- High levels of stress lower the protective ability of your immune system, leading to more frequent sickness.
Changes in appetite, either from loss of appetite or overeating, may be due to stress.
Epinephrine released by the adrenals can shut down appetite in the short term.
But in the long-term, stress can increase appetite. Elevated cortisol can increase cravings for sugary or fatty foods, foods that have a feedback effect that lowers stress-related responses and emotions . Since these foods physically help lower feelings of stress in the moment, they may contribute to stress-induced cravings.
Stress can also affect appetite by altering the production of leptin and ghrelin, hormones responsible for hunger and fullness cues. Leptin, the hormone that makes you feel full, is lowered following a stressful event .
Frequent unexplained headaches may be a physical symptom of an altered stress response.
Stress can both cause headaches and make headache intensify. This can be caused by increased muscle tension held in the neck and shoulders or from a clenched jaw. High blood pressure and changes in appetite, either from under-eating or over-eating, associated with stress can also contribute to headaches.
Encountering stressors throughout daily life is unavoidable. However, managing stress is something you can control. Below are some ways you can improve your body's ability to handle stress.
Considering how strongly sleep and stress are linked, it's important to prioritize rest. While it's recommended to sleep 7-9 hours per night, many Americans sleep 6 hours or less.
Tips to improve sleep quality and quantity:
- Go to bed and waking up at similar times each day
- Lower light exposure before bed from bright lights and screens
- Get outside: Exposure to full spectrum sunlight in the morning causes our brains to produce serotonin, stops the production of melatonin, and resets your circadian rhythm
- Do something calming before bed like taking a hot shower, reading, or meditating
Diet plays a big role in how we feel. As discussed2, stress responses can alter our appetite and what foods we crave.
Research shows that elevated cortisol combined with high sugar consumption "may prompt the deposition of fat around our internal organs-visceral fat that is associated with cardiovascular and metabolic diseases" .
Eating a variety of nutrients can help regulate blood sugar (which is more sensitive when stressed) and ensure your body is getting the nutrients it needs.
Regular physical exercise can improve sleep and decrease overall stress. Exercise lowers levels of adrenaline and cortisol while also stimulating the production of endorphins, feel-good chemicals in the brain.
Lastly, checking in with your mindset is important. A research-supported tool for stress is CBT, or cognitive behavioral therapy. This approach is based on the process that thoughts affect emotions which affect actions. "Reframing your thoughts around a stressor can help manage your emotions, reducing feelings of stress" .
This could look like being aware of how worst-case scenario thinking affects stress levels and trying to reframe to more positive thoughts. If additional support is needed, seek out a professional mental health provider who can help with stress management.
- Understanding the stress response. Harvard Health. (2020, July 6). Retrieved July 25, 2022, from https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response
- Cortisol: What it is, function, symptoms & levels. Cleveland Clinic. (2021). Retrieved July 26, 2022, from https://my.clevelandclinic.org/health/articles/22187-cortisol
- Heart rate variability: The ultimate guide to HRV. WHOOP. (2021, August 11). Retrieved July 25, 2022, from https://www.whoop.com/thelocker/heart-rate-variability-hrv/
- Schubert, C., Lambertz, M., Nelesen, R. A., Bardwell, W., Choi, J.-B., & Dimsdale, J. E. (2009, March). Effects of stress on heart rate complexity--a comparison between short-term and chronic stress. Biological psychology. Retrieved July 25, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2653595/
- American Psychological Association. (2013). Stress and sleep. American Psychological Association. Retrieved July 26, 2022, from https://www.apa.org/news/press/releases/stress/2013/sleep
- Buckley, T. M., & Schatzberg, A. F. (2005, May 1). On the interactions of the hypothalamic-pituitary-adrenal (HPA) axis and sleep: Normal HPA Axis activity and circadian rhythm, exemplary sleep disorders. OUP Academic. Retrieved July 25, 2022, from https://academic.oup.com/jcem/article/90/5/3106/2837129
- Why stress causes people to overeat. Harvard Health. (2021, February 15). Retrieved July 25, 2022, from https://www.health.harvard.edu/staying-healthy/why-stress-causes-people-to-overeat
- Bouillon-Minois, J.-B., Trousselard, M., Thivel, D., Benson, A. C., Schmidt, J., Moustafa, F., Bouvier, D., & Dutheil, F. (2021, September 24). Leptin as a biomarker of stress: A systematic review and meta-analysis. Nutrients. Retrieved July 25, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8541372/
- Thorn , B. (2013, November). Healthy ways to handle life's stressors. American Psychological Association. Retrieved July 25, 2022, from https://www.apa.org/topics/stress/tips
- American Psychological Association. (2019, October). Manage stress: Strengthen your support network. American Psychological Association. Retrieved July 26, 2022, from https://www.apa.org/topics/stress/manage-social-support
- Cortisol: What it is, function, symptoms & levels. Cleveland Clinic. (n.d.). Retrieved July 26, 2022, from https://my.clevelandclinic.org/health/articles/22187-cortisol