Whether from a charging lion, or a pending deadline, the body’s response to stress can be both helpful and harmful. The stress response gives us the strength and speed to ward off or flee from an impending threat. But when it persists, stress can put us at risk for obesity, heart disease, cancer, and a variety of other illnesses.
Perhaps the greatest understanding of stress and its effects has resulted from a theory by George Chrousos, M.D., Chief of the Pediatric and Reproductive Endocrinology Branch at the National Institute of Child Health and Human Development (NICHD).
A threat to your life or safety triggers a primal physical response from the body, leaving you breathless, heart pounding, and mind racing. From deep within your brain, a chemical signal speeds stress hormones through the bloodstream, priming your body to be alert and ready to escape danger. Concentration becomes more focused, reaction time faster, and strength and agility increase. When the stressful situation ends, hormonal signals switch off the stress response and the body returns to normal.
But in our modern society, stress doesn’t always let up. Many of us harbor anxiety and worry about daily events and relationships. Stress hormones continue to wash through the system in high levels, never leaving the blood and tissues. And so, the stress response that once gave ancient people the speed and endurance to escape life-threatening dangers runs constantly in many modern people and never shuts down.
Effects on reproductive system
Stress suppresses the reproductive system at various levels. For example, stress hormones inhibit the testes and ovaries directly, hindering production of the male and female sex hormones testosterone, estrogen, and progesterone.
The gastrointestinal tract and stress
Stress can result in digestive problems. Stress hormones directly hinder the release of stomach acid and emptying of the stomach and can directly stimulate the colon, speeding up the emptying of its contents.
Also, continual, high levels of cortisol – as it occurs in some forms of depression, or during chronic psychological stress – can increase appetite and lead to weight gain. Overeating at night is also common among people who are under stress.
The immune system and stress
Stress interacts with the immune system, making you more vulnerable to colds and flu, fatigue and infections.
In addition, the high cortisol levels resulting from prolonged stress could serve to make the body more susceptible to disease by switching off disease-fighting white blood cells.
Conversely, too little corticosteroid, can lead to a hyperactive immune system and increased risk of developing autoimmune diseases – diseases in which the immune system attacks the body’s own cells. Overactivation of the antibody-producing B cells may aggravate conditions like lupus, which result from an antibody attack on the body’s own tissues.
One of the major disorders characteristic of a chronic stress is melancholic depression. Chrousos’ research has shown that people with depression have a blunted ability to “counterregulate,” or adapt to the negative feedback of increases in cortisol. The body turns on the “fight or flight” response, but is prevented from turning it off again. This produces constant anxiety and overreaction to stimulation, followed by the paradoxical response called “learned helplessness,” in which victims apparently lose all motivation.
Hallmarks of this form of depression are anxiety, loss of appetite, loss of sex drive, rapid heartbeat, high blood pressure, and high cholesterol and triglyceride levels.
Other conditions are also associated with long-term stress.
These include anorexia nervosa, malnutrition, obsessive-compulsive disorder, anxiety disorder, alcoholism, alcohol and narcotic withdrawal, poorly controlled diabetes, childhood sexual abuse and hyperthyroidism.
The excessive amount of the stress hormone cortisol produced in patients with any of these conditions is responsible for many of the observed symptoms. Most of these patients share psychological symptoms including sleep disturbances, loss of libido, and loss of appetite as well as physical problems such as an increased risk for accumulating abdominal fat and hardening of the arteries and other forms of cardiovascular disease. These patients may also experience suppression of thyroid hormones, and of the immune system.
Although many disorders result from an overactive stress system, some result from an under-active stress system.
For example, in the case of Addison’s disease, lack of cortisol causes an increase of pigment in the skin, making the patient appear to have a tan. Other symptoms include fatigue, loss of appetite, weight loss, weakness, loss of body hair, nausea, vomiting, and an intense craving for salt.
Lack of the corticotropin-releasing hormone (CRH) also results in the feelings of extreme tiredness common to people suffering from chronic fatigue syndrome. Lack of CRH is also central to seasonal affective disorder (SAD), the feelings of fatigue and depression that plague some patients during winter months.
Chrousos and his team showed that sudden cessation of CRH production may also result in the depressive symptoms of postpartum depression. In response to CRH produced by the placenta, the mother's system stops manufacturing its own CRH. When the baby is born, the sudden loss of CRH may result in feelings of sadness or even severe depression for some women.
Source: National Institute of Child Health and Human Development (NICHD)