Spring Break Sniffles

Why do we get sick on vacation?

Posted Apr 16, 2018

Belinda Yew, used with permission
Source: Belinda Yew, used with permission

This guest post was contributed by Belinda Yew, a graduate student in the USC Psychology Department's Clinical Science program.

Life is full of great mysteries. What happens to all the ships and planes that go missing in the Bermuda Triangle? Is there life on Mars? Why do you always run into people you want to impress when you look like your shower has been broken for a month? How are you able to survive for weeks on meager food, sleep and exposure to natural light only to fall sick when finals are over and spring break rolls around? While experts are still working on the first three, the answer to our last question may be found in the field of psychoneuroimmunology.


Psychoneuroimmunology is essentially the study of how our psychological (thoughts, behaviors), neurological (brain and nervous system), and immune functions interact. While most of us know that smoking a pack of cigarettes for breakfast or braising ourselves on the beach all day sans sunscreen can hurt our health, research suggests that stressors like feeling lonely and chronically worrying about midterm papers may be just as harmful. Put simply– both physical and mental wellbeing influence health. 

Pixabay, Creative Commons license
Source: Pixabay, Creative Commons license

In the mid-eighties, researchers at the Ohio State University convinced almost 100 freshman med students to provide blood samples both before and during their finals. The researchers were particularly interested in the students’ natural killer cells (immune cells that exist to, as their name suggests, bring a quick and speedy death to any pathogens they encounter). Interestingly, blood collected during exams contained significantly fewer killer cells than samples collected a month earlier, suggesting that even the stress of college finals can diminish immune function.

Over a decade later, in an even pluckier batch of Ohio State students, researchers studied the effects of academic stress on wound healing. Bored by the sunny, school-free days of summer vacation, the students signed up to receive superficial mouth wounds and answer questions about their stress levels. Each day after this, an unfortunate researcher was tasked with measuring the students’ wounds until healing was complete. The same stress questionnaire and wound infliction-plus-measurement procedures were then repeated later in the year, right before finals. As expected, students’ stress ratings sky-rocketed during exams. Thanks to some A+ wound measuring, however, researchers were also able to show that mouth wound repair was 40 percent slower during finals versus summer break. These effects held even when they accounted for the sleep deprivation and caffeine overloading that typifies exam season, so it’s likely that stress rather than other exam-related factors interfered with healing.

Pixabay, Creative Commons license
Source: Pixabay, Creative Commons license

Notably, the health-depleting powers of stress are not restricted to students over-burdened by exams (and apparently, research participation). Comparable findings have been seen in recently widowed individuals, caregivers of dementia patients, people with chronically high job stress, and people lacking social support, suggesting that various types of stress can affect immune function. Furthermore, this stress doesn’t just impede our ability to stave off disease but also compromises the effectiveness of vaccines.

Unsurprisingly, enduring stressors such as poverty and ongoing domestic abuse exact the largest tolls on health. With prolonged immunosuppression, our bodies become ripe for more serious illnesses like cancer.

How does stress influence immune function?

So how exactly does the caffeine-fueled chaos of finals week or the superhuman productivity of the month leading up to your team’s project deadline, end with you relegated to your bed, swimming in an ocean of snot? For those of us who haven’t gotten around to completing advanced degrees in neuroendocrinology just yet, the science goes something like this:

Whether it is caused by a hungry T-rex hot on your heels or a daunting job interview, stress tends to trigger the same ol’ fight-or-flight response. Breathing speeds up, your heart beats faster (to pump the blood needed for delivery of your muscles’ massive energy order), you take a break from digestion and growing, your senses become hyper-focused, and after some time, immune function is dampened.

Why does it help to curb immune function when you’re facing imminent threat? While your immunity may momentarily heighten at the sight of a hungry (albeit historically misplaced) dinosaur, over time, your body tries to lower it back to baseline. Running your immune system on full-throttle is a costly process and, if prolonged, can lead to harmful effects on the body. Immune activation not only drains resources but can become hypersensitive, occasionally mistaking your own cells for invaders, which can lead to nasty autoimmune disorders like rheumatoid arthritis and celiac disease. Processes that lower immune function can therefore be adaptive in the face of short-term (think less than an hour) threats.

With longer-term stressors, however, attenuated immunity is prolonged for months and even years. Furthermore, behaviors commonly associated with extended stressful situations (e.g. drinking, sleeping less, and smoking) can exacerbate this threat to our health. The thrill of printing the final page of your report may therefore coincide with your weakened immune system’s defeat by colds or flus that it would usually conquer effortlessly. Instead of celebrating and relaxing, your well-earned Spring break now consists of tea-drinking and using your body weight in tissues.

What can we do?

If you’re anything like me, learning that stress can literally kill you probably has your anxiety approaching ulcer-inducing levels by the second. How do we get off this runaway train to disease town? The good news is there are a number of proven ways to minimize stress and promote healthy immune function:

Diet. This may seem obvious but eating a nutritious diet that is low in sugary, processed foods can reduce inflammation and keep your body running how it should. Foods that are high in vitamin C (e.g. citrus fruits, bell peppers, kiwi) and omega-3 (e.g. salmon, walnuts, and flax) may also reduce cortisol, a stress hormone.

Meditation. Regular meditation reduces stress and may even improve immune function directly. The best part is you don’t need inordinate hours or wind chimes to find your “inner peace.” Even a few minutes of practice can produce improvements in mindfulness.

Breathing. Deeper, slower breathing enables the complete filling of your lungs so that more oxygen can be taken into your body with each breath. Deep breathing also lowers heart rate and blood pressure, evoking a relaxed sensation that has been shown to lower stress.

Friends. Loneliness and social isolation have been linked to higher morbidity and mortality. In contrast, good social support can buffer against stress, resulting in improved immune and cardiovascular function. Spending time with people who love and care about you may be just as potent as those unholy juice cleanses.

Smiling. While being told to “grin and bear” your stress or “put on a happy face” can be infuriating, there may be some truth to these adages. Even fake smiling has been shown to speed up physiological recovery from stress.

These are just a few of the multitude of stress-reduction techniques available. As scientists, health care providers, and legislators increasingly recognize the importance of stress management for health, we can expect to see the list grow. In the meantime, know that stress is an inevitable but largely manageable part of life. As legendary singer and civil rights activist Lena Horne once said, “it’s not the load that breaks you down, it’s the way you carry it.”


Black, D.S. & Slavich, G.M. (2016). Mindfulness meditation and the immune system: A systematic review of randomized controlled trials. Annals of the New York Academy of Sciences, 1373, 13-24.

Glaser, R., Kiecolt-Glaser, J.K., Bonneau, R.H., Malarkey, W., Kennedy, S., & Hughes, J. (1992). Stress-induced modulation of the immune response to recombinant hepatitis B vaccine. Psychosomatic Medicine, 54, 22-29.

Kiecolt-Glaser, J.K., Garner, W., Speicher, C., Penn, G.M., Holliday, J., & Glaser, R. (1984). Psychosocial modifiers of immunocompetence in medical students. Psychosomatic Medicine, 46, 7-14.

Kraft, T.L., & Pressman, S.D. (2012). Grin and bear it: The influence of manipulated facial expression on the stress response. Psychological Science, 23, 1372-1378.

Mahmood, L., Hopthrow, T., Randsley de Moura, G. (2016). A moment of mindfulness: Computer-mediated mindfulness practice increases state mindfulness. PLOS One, 11, e0153923.

Marucha, P.T., Kiecolt-Glaser, J.K., & Favagehi, M. (1998). Mucosal wound healing is impaired by examination stress. Psychosomatic Medicine, 60, 362-365.

Segerstrom, S.C. & Miller, G.E. (2004). Psychological stress and the human immune system: A meta-analytic study of 30 years of inquiry. Psychological Bulletin, 130, 601-630.

Uchino, B.N., Cacioppo, J.T., & Kiecolt-Glaser, J.K. (1996). The relationship between social support and physiological processes: A review with emphasis on the underlying mechanisms and implications for health. Psychological Bulletin, 119, 488-531.

More Posts