Every semester I check my attendance records an a pattern becomes abundantly clear: in the two or three weeks before final exams, attendance drops off. Some people will toss me an email explaining why, and almost always the reason is illness. Many of you have probably noticed that this trend takes the form of “just when I have all these other things to take care of, all of a sudden I’m sick. Figures.”
Yes, it does figure. In fact, it makes perfect sense – when you consider the immune modulation effects of stress. I mean, I guess I’m going out on a limb by assuming that finals, exams, and papers might be stressing you out, especially when they’re happening all at once. But it’s a pretty safe assumption that you’re sleeping less, exercising less, eating worse, and spending less time relaxing than you might have during the rest of the semester. If you know anything about my habits, it’s a pretty good explanation for why I get four colds every year: one every semester right around the first class, and one just before finals. Both periods of illness correspond to periods of peak stress.
The general idea is that stress can cause a couple of side effects: firstly (and directly) the release of cortisol during periods of stress decreases activity in the immune system, leading to increased risk of infection. This is generally associated with chronic stress. The second cause of symptoms is acute stressors stimulating the release of leukocytes and, in turn, cytokines – which cause an inflammatory response in the body, even though there is no infection to fight.
The second example has some pretty clear value. The stress response isn’t just associated with psychological stressors like exams; it’s also associated with increased physical activity and what comes with it – risk of injury. To protect itself from the risk of infection due to an injury, the body temporarily increases the immune response during a period of acute stress. Basically, the brain anticipates that an infection might occur, and releases white blood cells (leukocytes) and cytokines, and these will cause inflammation. It’s the inflammation which you experience as things like headaches, joint pain, fever, and swollen glands. The great irony is that you’re not actually sick, but your immunological response causes you to feel as if you are.
The first example is more of a problem in the long run. Long-term stress is associated with generally increased levels of cortisol, which suppresses immune function. This leaves the body vulnerable to opportunistic infections. Studies routinely show that individuals with higher-than-average levels of chronic stress heal more slowly than their less-stressed counterparts. Studies have also shown that opportunistic infections – ranging from gingivitis, pericarditis, and bronchitis to HIV and some cancers – progress faster and are harder to cure in individuals with higher levels of stress.
This is in line with Hans Selye’s theory of general adaptation syndrome, in which the effect of long-term exposure to cortisol (and other stress hormones) eventually causes irreversible organ damage, decreased immune function, physical and psychological exhaustion, and even death. Selye is more or less saying that the body’s stress response is not an unlimited resource, and will eventually deplete itself to the point that continued resistance to the stressor can only be sustained by cannibalizing other resources, such as body fat and muscle. Eventually, even organ tissues become involved in the process.
Studies on the impact of stress (broken down by socio-economic status) show that mortality rates trend along with the frequency of economic stressors, and that class differences in death rates might be anchored around relative levels of stress. Wealthier individuals with a more leisurely lifestyle have fewer infections, lower rates of cancer, and live longer. Poorer individuals who spend more time working and worrying about making ends meet experience more infections, slower rates of healing, higher rates of cancer, and more deaths due to cardiovascular diseases. Of course there are other differences in lifestyle between these groups which could contribute to differing mortality rates, but stress is definitely a factor – and stress motivates many other behaviors (such as drug and alcohol abuse) which may also increase mortality rates.
Basically, I’m saying that stress kills, and why you’re conveniently sick during periods when being sick is actually really, really inconvenient.
General Psychology 