Chronic Stress

  • Published1 Apr 2012
  • Reviewed1 Apr 2012
  • Source BrainFacts/SfN

What do standing frustrated in a supermarket checkout line or sitting in a traffic jam have in common with fleeing predators, as was done in the early days of human beings?

Clearly, these activities are very different, yet they provoke the same responses in the body— the release of hormones (glucocorticoids and epinephrine) to improve memory, boost immune function, enhance muscular activity, and restore physiological balance. Over long periods of time, as these hormones continue to be released, the consequences can be negative: memory is impaired, immune function is suppressed, and energy is stored as fat.

Overexposure to glucocorticoids leads to weakened muscles. Elevated glucocorticoids and epinephrine contribute to hypertension (high blood pressure), atherosclerosis (hardening of the arteries), and abdominal obesity. Epinephrine also increases the release and activity of body chemicals that cause inflammation, adding to the body’s chronic stress burden. This continual chemical activity can lead to arthritis and accelerated aging of the brain.

These findings have been verified in animal experiments. Aging rats show impaired neuron function in the hippocampus — an area of the brain important for learning, memory, and emotion — as a result of increased glucocorticoid secretion throughout their lives. Overexposure to glucocorticoids also increases the number of neurons damaged by stroke. Moreover, prolonged glucocorticoid exposure before or immediately after birth causes a decrease in the normal number of brain neurons and smaller brain size.

What’s more, scientists have identified a variety of stress-related disorders, including high blood pressure, clogged arteries, impotency and loss of sex drive in males, irregular menstrual cycles in females, colitis, and adult-onset diabetes. Stress also can contribute to sleep loss when people get caught in a vicious cycle: elevated glucocorticoids delaying the onset of sleep, and sleep deprivation raising glucocorticoid levels.