You lose your kid at the grocery store. You forget about a deadline at work. You have 40 things to do today and only time for 12. As mental pressure builds, the body responds physically to try to protect itself in a fight-or-flight response.
Studies on stress began in the 1930s when Hungarian-Canadian scientist Hans Selye coined the term and conducted a series of experiments on lab animals. The animals were subjected to various non-harmful forms of stress, and they all showed negative physical effects, according to the American Institute of Stress.
Long-term studies on these animals correlated persistent stress with increased likelihood of chronic illness, heart attacks and strokes.
Since Selye’s studies, research on stress has narrowed in on five physical symptoms of stress.
What are the physical symptoms of stress?
1. Headaches
Stress causes muscle contraction. Rehabilitation therapist David Munson, explained, “When stress levels are high, our brain sends a signal to the nerves to go into ‘protection mode,’ and our nerves activate our muscles to tighten and increase their tone,” per TriHealth.
Headaches caused by stress feel like “constant mild to moderate pressure and pain,” like something is “squeezing the sides” of your head, “aching or tight neck muscles and shoulder muscles,” and a sensitivity to bright lights and loud sounds, according to Cleveland Clinic.
While tension headaches can be caused by arthritis, they can also be caused by looking at too many screens or straining your neck for long periods of time. These symptoms can last anywhere from 30 minutes to a week.
2. Upset stomach
Stress can cause multiple stomach issues, including bowel movement changes and stomach pain.
In a study conducted by Vanderbilt University, Dr. Howard Mertz described the digestive system and the stomach as particularly susceptible to stress. He said, “Common gastrointestinal symptoms due to stress are heartburn, indigestion, nausea and vomiting, diarrhea, constipation and associated lower abdominal pain.”
According to UChicago Medicine, “When you’re stressed, the nervous system sends signals to your gut and your intestines, triggering the muscles involved in digestion to go into a ‘flight or fight’ response.”
Mertz described a study conducted to observe rodents’ physical response to stressful situations. To induce stress, researchers restrained rats or placed them “on a small platform surrounded by water.”
While in these stressful situations, the rats’ bowel movements in their small intestines slowed down significantly. Mertz described this as “a defense mechanism to promote vomiting and reduce oral intake.”
However, the rats’ bowel movements through their large intestines sped up, and stool output increased. “This may be a defense mechanism to eliminate toxins,” Mertz wrote.
Another study published by the National Institute of Health investigated the relationship between stomach pain and stress and showed that individuals with chronic stress are more likely to have irritable bowel syndrome and Type 2 diabetes.
3. Weakened immune system
A study by the American Psychological Association showed how short-term stress can strengthen the immune system, but long-term stress is correlated with lower lymphocyte levels, and consequently a weaker immune system.
Lymphocytes are white blood cells that protect the body from infections and diseases.
“There are several other studies which demonstrated a relationship between psychological stress and susceptibility to several cold viruses,” the NIH commented. The study added, “This is not surprising as stress does suppress the immune system.”
The bigger the stress, the bigger the impact it will have on your body’s overall health. APA reported, “Stressors that turn a person’s world upside down and appear to offer no ‘light at the end of the tunnel’ could have the greatest psychological and physiological impact.”
4. Insomnia
In the past month, 43% of Americans have laid awake as a result of stress, according to data published by the American Psychological Association. The study added, “Most Americans would be happier, healthier and safer if they were to sleep an extra 60 to 90 minutes per night.”
Professor of neurology Dr. Annise Wilson explained how stress influences sleep to the Baylor College of Medicine.
“High levels of stress impair sleep by prolonging how long it takes to fall asleep and fragmenting sleep,” she said. “Sleep loss triggers our body’s stress response system, leading to an elevation in stress hormones, namely cortisol, which further disrupts sleep.”
Wilson referred to research showing sleep influencing learning and memory, adding, “Chronic sleep deprivation also has been associated with decreased metabolism and endocrine dysfunction.”
Short-term insomnia is usually a result of “stress or a distressing event,” according to the Mayo Clinic. Once insomnia reaches three months or more, doctors classify it as long-term and recommend seeing a doctor.
5. Trouble breathing
Australian integrated breathing therapist Dr. Rosalba Courtney described breathing as both voluntary and automatic.
Because trouble breathing is a common side effect of intense stress, Courtney explained, “If our brain and nervous system perceives we are under (physical or psychological) threat, these involuntary automatic processes stimulate our breathing in preparation for imminent fight or flight,” she wrote.
American scientists have correlated stress with trouble breathing for over a century.
Psychiatrist Eric Lindemann famously wrote in 1942 that the physical symptoms of the stress that accompany grief include “sensations of somatic distress occurring in waves lasting from 20 minutes to an hour at a time, a feeling of tightness in the throat, choking with shortness of breath, need for sighing and an empty feeling in the abdomen, lack of muscular power, and an intensive subjective distress described as tension or mental pain.”