As discussed in one of my previous posts, stress is an ambiguous, all-encompassing construct that people often use to label both physically and psychologically suboptimal states in which an individual is struggling to cope with the demands placed on him or her. You may say your body experiences stress when attempting to escape from an attacker, but you could also be stressed just worrying about an upcoming presentation. Despite these very different scenarios, the term “stress” is used to describe both states. Stress not only has a broad definition but also is broadly implicated in society as a major cause for anything from mild medical concerns such as catching a cold to more serious diseases such as cancer and even psychological conditions such as depression. But do these charges hold true? With this popular narrative it is easy to retrospectively identify stress as a cause for poor health outcomes, but does the evidence actually support this assertion?
First, let’s take a look at the simplest (i.e., short-term) health concern: infectious disease. Our body defends itself from infectious disease through a complex immune system (Sapolsky, 2004). Innate immunity is our first line of defense, and is a nonspecific response to infectious agents that causes inflammation. Acquired immunity, on the other hand, is a more complex system that allows us to target a specific pathogen, build up immunity against it, and boost our defenses if the same pathogen shows up in the future.
So how does stress impact our immune system? At first, stress appears to enhance it (Sapolsky, 2004). However, if the stressor is too intense or continues for too long, it may actually lead our immune system not only to return to baseline levels, but also subsequently to plummet further. For example, stress may enable you to push through that exam week without getting sick, but just when you’re arriving home for the holidays you may find you’ve succumbed to the flu. Alternatively, if you’re constantly overworked and sleep deprived you may find yourself catching a cold more easily. Indeed, Cohen et al. (2012) found that recently experiencing a long-term threatening stressor increased participants’ risk of getting a cold. In fact, they demonstrated the mechanism behind the effect: stress led participants to demonstrate glucocorticoid receptor resistance (GCR), those with greater GCR were at higher risk of catching a cold, and greater GCR also predicted greater inflammation in infected participants.
Interestingly, while stress can impact how our immune system operates, our immune system can also affect how we are impacted by stress. Hodes, Kana, Menard, Merad, and Russo (2015) found that our peripheral immune system alters our response to stress and can make us vulnerable to mood disorders such as depression. Dysregulated immune responses to stress may cause inflammation, which in turn may contribute to depressive symptoms. Thus, our physiology and psychology are intimately connected when it comes to stress and its impact on health.
The more immediate effects of stress on our immune system and ability to fight off infectious may be clear, but what about more long-term diseases such as cancer? Despite popular belief amongst the general population and cancer patients that stress contributes to the onset and worsening of cancer, the evidence for this is mixed and studies showing a connection are often flawed as they use retrospective methods (Sapolsky, 2004). One large-scale, prospective study, on the other hand, found that self-reported frequency of stress and adverse life events did not affect future breast cancer risk (Schoemaker et al., 2016). This disconnect between popular belief and scientific evidence could be detrimental as it has the potential to lead to ineffective preventative techniques and treatments. Thus, it seems critical that we improve health-related education as it relates to stress so that lay people do not mistakenly use stress as a catch-all explanation for poor health.
Cohen, S., Janicki-Deverts, D., Doyle, W. J., Miller, G. E., Frank, E., Rabin, B. S., & Turner, R. B. (2012). Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. Proceedings of the National Academy of Sciences, 109(16), 5995-5999.
Hodes, G. E., Kana, V., Menard, C., Merad, M., & Russo, S. J. (2015). Neuroimmune mechanisms of depression. Nature neuroscience, 18(10), 1386.
Sapolsky, R. M. (1994). Why zebras don’t get ulcers. New York: WH Freeman.
Schoemaker, M. J., Jones, M. E., Wright, L. B., Griffin, J., McFadden, E., Ashworth, A., & Swerdlow, A. J. (2016). Psychological stress, adverse life events and breast cancer incidence: a cohort investigation in 106,000 women in the United Kingdom. Breast Cancer Research, 18(1), 72.