How Stress Makes Us Sick
Keely Muscatell, PhD, is a social neuroscientist and psychoneuroimmunologist. She is a post-doctoral scholar in the Robert Wood Johnson Foundation (RWJF) Health & Society Scholars program at the University of California (UC), San Francisco and UC, Berkeley.
Results from the recent NPR/RWJF/Harvard School of Public Health poll suggesting that Americans are living under high levels of stress probably don’t surprise anyone. In a way, I’ve been taking an informal version of this poll for the last six years, since when I tell people I meet on airplanes or at local bars that I study stress and health, I am unfailingly met with knowing glances and stories about stressors people are facing in their lives. Given that stress is pervasive (and problematic) in modern life, lots of current research in psychology and neuroscience is focused on understanding exactly how stress can get “into our brains” and “under our skin” to make us sick.
When we think of illness, one of the first things that comes to mind is the immune system, with its lymph nodes, white blood cells, and antibodies hanging around to help us fight off infections and heal our injuries. An especially important component of the immune system involves inflammation. If you’ve ever gotten a paper cut, you’ve probably noticed that the area of skin around the cut tends to turn red and warm up shortly after the injury. This happens because proteins called “pro-inflammatory cytokines” swim through your blood stream to the site of the wound, where they call out to other immune cells to come to the area and help heal the cut. In the short term, this is a good thing; those little cytokines are a key part of healing. But if inflammation becomes widespread throughout the body, cytokines can lead to depression and even physical diseases, like arthritis and heart disease.
But what does any of this have to do with stress? A number of studies in a relatively new field called psychoneuroimmunology have shown that stress on its own can cause inflammation. In other words, the immune system can be activated by our thoughts and feelings, even when there aren’t any cuts to heal or infections to fight.
Researchers have found that people who are under a lot of chronic stress, like those living in poverty or caring for a sick parent, have higher levels of inflammation than people living under less stressful circumstances. Even short-term, mild stressors can cause inflammation: When people are asked to come to the lab and give a short speech in front of panel of disapproving strangers, the number of cytokines in their bloodstream increases. In fact, in a recent study I conducted with colleagues at UCLA, we showed that even just being told by a peer that you’re “annoying” or “boring” is enough to increase inflammation.
Maybe it’s time to revise that age-old saying about sticks and stones, as it seems that names can hurt—and fire up the immune system as well. And that, in turn, could be making us sick.
Of course, there are many people in the United States who are faced with stress on a daily basis and still go on to live long, healthy, happy lives. In fact, in the study mentioned above, some participants seemed to just let the negative feedback roll off their backs, while others were visibly upset by it. One participant even asked me two hours after the feedback if I thought she seemed annoying; clearly she was ruminating about the experience and self-conscious about the way she had come across.
This Is Your Brain on Stress
To try and get a handle on why some people are especially sensitive to the negative effects of stress while others are resilient to it, we examined what was happening in the brains of our participants while they received negative feedback from a peer. Using functional MRI scanning (which allows us to track what parts of the brain are being used over time), we measured how participants’ brains responded to being told they were “annoying” and “boring,” in addition to measuring their levels of inflammation. We found that people who showed more neural activity in the amygdala—an ancient, animalistic brain structure involved in emotion and threat—also had bigger increases in inflammation. So it seems that people who responded to stress with more activity in this “emotion center” of the brain also had more reactive immune systems, and therefore may be more likely to develop stress-related illnesses.
If you’re concerned that your amygdala may be firing non-stop and revving up your cytokines, fear not: Just changing the way you think in a stressful situation can calm down the amygdala and hopefully stop inflammation from increasing. A number of studies suggest that reframing the way you think during a stressor (what psychologists call “cognitive reappraisal” and a common technique in cognitive-behavioral therapy) can “turn down” an overactive amygdala. Other research suggests that simply labeling our emotions can help decrease the amygdala’s response, as can thinking about a loved one, writing about stressors in a journal, or even providing help and support to others rather than focusing on our own issues.
While we need much more research to fully understand how stress affects the brain and body, our research and that of many others is beginning to provide answers to the question of how stress makes us sick. Given the tremendous amount of stress that the NPR/RWJF/Harvard School of Public Health Poll revealed that we’re under, answering this question is of extreme importance to the health and longevity of our nation.