I personally understand that stress relates to our immune systems and susceptibility. Stress and other factors put our bodies to work in overdrive. They end up over worked and under paid and it leads to getting sick more often than the average person would. It doesn't surprise me that psycho social variables play a role in the human immune system. I never really thought how my high stress level could lead me to be more susceptible to infectious diseases, that is alarming. I am someone who is constantly in overdrive and my body definitely pays the price.