These heightened biological reactions work in our favor—for the short term. For the caveman, once the danger was over, the system returned to normal levels of functioning, and experienced long periods of little or no stress at all. Stress was short-lived and fleeting. In modern times, for many of us, we are drowning in constant waves of these stress-induced biological changes, with little or no return to baseline levels in between. That's when a normal stress response can begin to make us sick.
Too much ongoing stress (with little or no breaks in the cycle) can lead to a host of medical problems such as elevated blood pressure, heart attacks and compromised immune systems. That can lead to a greater incidence of colds, flu, infections, and even cancer. Long-term exposure to stress has been proven to contribute to infertility, and even speed up the aging process. The emotional effects of stress can cause overeating which might lead to obesity and the host of diseases that accompany it.
So why is it that stress, which seems to be something only in our minds, can have such an impact on our bodies? What is going on that causes almost every cell and organ to suffer from chronic stress? To put it simply, the body doesn't recognize the difference between physical threats or psychological threats, and it responds to both as life or death situations.
When you are under stress, your brain produces a series of chemicals that travel through your blood, wreaking havoc on almost every system in our body. Dr. Michael Roizen and Dr. Mehmet Oz described this stress circuit beautifully in their best-selling book, You: Staying Young. They state:
"Your stress circuit is the interaction between your nervous system and your stress hormones. This hormonal system is called the HPA axis. The hormones cycle through three glands in a feedback loop. When faced with a stressor, the hypothalamus at the base of our brain releases CRH (corticotrophin-releasing hormone), which then dances around the pituitary gland, stimulating another hormone called ACTH (adrenocorticotropic hormone) into our blood stream. ACTH signals the adrenal gland to release cortisol and norepinephrine (also known as adrenaline, the fight or flight chemical). Adrenaline increases your blood pressure and heart rate, while cortisol releases sugar in the form of glucose to fuel your muscles and mind. Then, cortisol travels back to the hypothalamus to stop the production of CRH once the stress is over, and the body returns to normal. But only if the stress stops as well."