The thymus gland pumps out millions of lymphocytes each day to patrol throughout the body and to kill off bacterial invaders. Killer cells called macrophages literally eat invading bacteria. They operate in all parts of the body and we depend on them for our survival. Macrophages are weakened by a steroid called cortisol which is released by the adrenal gland when we experience stress. A weakened immune system makes us vulnerable to infection and this is why people under stress often experience regular attacks of colds and flu.
Psychological stress does have physical ramifications.
We can do ourselves a great deal of harm by stressful thinking. We can flood our body with stress hormones and this can create a vicious cycle making us more and more stressful. Brain scientists are gradually moving away from the view that the brain is an electrically driven organ. Extensive research over the past 25 years has produced convincing evidence that hormones and not electricity is the stuff of thought. Many neurosurgeons are now persuaded that thinking is hormonal and that it takes place all over the body.