Stress and your immune system: Chill or be chilled.
Some stress is good. If you don’t have any stress, then you are probably dead or in a coma. I read somewhere about a tribe of natives that subsisted almost exclusively on nuts which grew in abundance. I thought that surely this would mean a life free of stress for these people. Now that I know a little about human nature, I realize that people create much of their own stress. Take the nut-gathering tribe for instance. I’ll bet some of the natives felt they had to have bigger, tastier, and more total nuts than the other natives. So even in this apparent Shangri-la, there may be keeping up with the Jones’s and all the jealousy, greed, pride etc. that go along with it.
I heard recently that women with breast cancer who excersize regularly have a significantly increased survival rate compared to those who don’t. Although it is likely that some of this effect relates to direct effects of exercize on the immune system and the down-regulation of estrogen production, I also believe some of the benefit has a psychological basis. This brings up a new and as yet underdeveloped sub-field within Immunology,which is called Psycho-neuro-immunology. This word is quite a mouthful, but it describes the area of study that examines the cross talk between our nervous system and our immune system.
The best understood way in which the nervous system impacts the immune system is through stimulating the production of hydrocortisone. Hydrocortisone is made by the adrenal glands in response to signals from the brain. When you are acutely stressed, the body tends to focus on short-term strategies for survival at the expense of long term strategies. For example, when you are being chased by a lion, a whole bunch of aspects of your physiology become of secondary importance to the coordinated contraction of skeletal muscles involved in running (and, in my case, screaming). One set of these temporarily neglected functions includes immunity. In other words, if you don’t out-run that lion, the ability of your leukocytes to fight a cold would mean didley squat. Hydrocortisone is one of the signals that temporarily depresses immunity when you are acutely stressed. The problem is that if you are acutely stressed too often, then your immune system will become chronically suppressed.
Hyrocortisone blocks an activation pathway inside of many of the cells of the immune system which normally stimulates, their migration, the signaling of other cells, killing of bacteria etc. One example of this that I love to tell my students about is a study which looked at the numbers of lymphocytes (the type of leukocytes which mediate acquired immune respones) in medical students at different times during the semester. What the study showed was that the number of lymphocytes in their blood dropped right before an exam and this correlated with a rise in hydrocortisone levels. These results suggested that the stress of studying for the exam stimulated the production of hydrocortisone in these students, which in turn, effected the migration of their lymphocytes.
I am not a psychologist so I am not going to say much about how to reduce the amount of stress in your lives. But I will tell you that if you suffer a lot of stress in your life, you need to find some way to chill or your immune system will suffer. Don’t get me wrong, I am not saying that being lazy will be good for your immune system. Remember the study involving breast cancer patients and excersize. Exercize, especially if it involves doing something you enjoy or something that brings a feeling of accomplishment, is one of the best stress reducers. There you have it: Chill or be chilled.