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Giving “Worried Sick” a Whole New Meaning

Research suggests everything from stress to your mood may affect your body’s immune response.

Everybody experiences stress differently, from the circumstances that cause it, to the ways that we cope with it. What doesn’t differ is that we all experience it, one way or another. There are a multitude of reasons why we get stressed: academic deadlines, social pressures and work-related responsibilities.

As a student, I notice my friends and I tend to get sick around finals season or catch the flu during that midterm week in February. While this seems like the worst luck ever, it might actually stem from a connection between your physical and mental health. The reasons are being studied extensively; however, there is evidence to suggest that psychosocial factors play a role in regulating the body’s immune system.

The immune system provides a set of defences to protect the body from possible invaders called pathogens. It operates through a vast number of cells, organs and pathways that are equally intricate as they are powerful. One particular pathogen-fighting group of white blood cells are called lymphocytes, which include T-cells, B-cells, and natural killer (NK) cells. T-cells will directly tackle invaders or produce cytokines, which act as signalling molecules that activate other elements of the immune system. B-cells are responsible for producing antibodies, which fight pathogens. And natural killer cells do exactly what their name suggests: kill infected cells. Although each cell has its own unique role, they have to work together for proper immunological function.

Let’s take a look at the intersection between the immune system and stress. From a biological standpoint, stress is defined as the body’s response when pushed beyond its limits or exposed to a foreign threat. In response to stress, a hormone called cortisol is released. Researchers have found that excessive levels of cortisol can suppress the activity of T-cells and B-cells, dampening the immune response. Since the elements of the immune system depend greatly on their cooperative function, there is a domino effect that extends beyond these lymphocytes. For example, the dysregulation of T-cells causes an imbalance in cytokines which are in charge of signalling for the immune response. As such, an excess of cytokines can hyperactivate the immune system, worsening asthma, allergies and autoimmune disorders.

More recently, the COVID-19 pandemic has exacerbated pre-existing stressors and taken a negative toll on many people’s mental health. Social isolation, separation from loved ones, travel bans and other abrupt life changes in the past year are some of many reasons for stress to be at an all-time high. With this increase in stress, comes an increase in cortisol in the body. A spike in cortisol levels can dysregulate the elements of the immune response, causing a rise in cytokine levels. In some cases, the immune system may produce an additional overexaggerated cytokine response to new viruses such as SARS-CoV-2, which is responsible for COVID-19. This response is commonly called the “cytokine storm”. Early literature suggests a strong link between COVID-19-related respiratory failure and the cytokine storm. However, more recent findings at Washington University School of Medicine called into question this relationship, with very few patients exhibiting the cytokine storm profiles leading to respiratory failure. Research involving COVID-19 continues to evolve rapidly, but this example highlights the complexity of the immune system.

A study conducted at the Leibniz Research Centre explored the difference in immunity after exposure to short-term and long-term stress. For short-term stressors, such as taking an exam, they found a significant reduction of NK cells, cytokines, and other immune cells called monocytes. The researchers subjected participants to academic stress then measured cortisol levels in their saliva and immune cells in their blood. They found long-term stress worsened pre-existing illnesses such as diabetes, irritable bowel syndrome, heart disease or schizophrenia. A similar study conducted at the Ohio State University College of Medicine found that medical students had suppressed immunity for one three-day exam period each year. During this period of time, the participants exhibited a reduced NK cell count, and virtually no production of T-cells. While we feel stress mentally, it takes a toll physically as our body is less capable of fighting pathogens and protecting us from disease.

On the other hand, some studies link positive mood to increased immunological function. Researchers commonly assess this by testing the antibody levels of a patient following a vaccination. One study found that individuals in a positive mood produced a 73% greater antibody response to a hepatitis B vaccine than participants in a negative mood. Another study found greater antibody response in individuals who had a support system of close friends. A group of students receiving a flu shot filled out a survey assessing their level of social support. Then, researchers used the students’ blood tests to measure antibody levels.

Another study investigated laughter as a positive emotional stimulus; the researchers found that patients had increased NK cell function after watching an hour of funny videos. They observed the same increase in NK and T cell activity following an eight-week stress reduction program. So, when you go in for your next flu shot or your COVID-19 vaccination, keep in mind that being optimistic might help gear up your immune system to protect against pathogens.

While your mood may not cause a cold nor cure the flu, it can affect the way your body mounts its immune response. All that to say — taking care of your mental health in turn maintains your physical health too. See the list below for McGill resources on mental health and wellness.


Local Wellness Advisors (LWAs) at McGill are trained clinicians embedded within faculties and services to orient and connect you with the appropriate support resource - on-campus or off-campus - for your unique situation. LWAs also offer wellness programming tailored to your faculty and work with departments on wellness awareness, prevention and early intervention.

Keep.meSAFE is a mental health counselling service offered to students in partnership with the undergraduate and graduate students’ societies (SSMU and PGSS). It provides 24/7 access to licensed counsellors through telephone and mobile chat in more than 60 languages. To access this service, download the MySSP app in the Apple App Store or Google Play.

The Peer Support Center provides free, one-on-one, confidential and non-judgmental peer support and resource referral to all McGill students.

McGill Students’ Nightline is a confidential, anonymous, and non-judgmental listening service run by McGill students. They aim to provide the community with non-professional support in all kinds of situations, including information, guidance during a crisis, or an empathetic space to share your experiences and emotions.

Cat Wang is a biomedical science student at McGill University, specializing in anatomy and cell biology.


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