Are you tired, irritable, or regularly experiencing headaches? Or perhaps you just can’t sit still? Have you been coming down with a cold every other week? Or constantly navigating tummy troubles? Is that shoulder or back ache still stubbornly bothering you? And on top of that, you seem to have a new pimple every day. In any case, if much of this applies to you, you may be stressed. As the World Health Organisation defines it, stress is a state of worry or mental tension caused by a difficult situation. But how can worrying or mental tension make you sick or give you tummy troubles? How does stressing about an exam affect the inside of your body and your industrious little cells? If you delve into reading about stress, one hormone inevitably pops up: the stress hormone, cortisol. Your body releases cortisol when the hypothalamus-pituitary-adrenal axis or HPA axis is activated. Here’s how the HPA axis works. When you’re stressed, either from an imminent tiger attack or a fast-approaching deadline, a cascade of events occurs in your body. Your nervous system will initiate your fight-or-flight response and your adrenal glands will release adrenaline, giving you an adrenaline boost. If the stress persists beyond a few hours, the amygdala—the part of your brain that senses danger—will alert another part of the brain called the hypothalamus. This will cause a cascade of hormones to be released. Briefly, this is what happens. The hypothalamus releases a hormone that signals the pituitary gland, which is also in the brain, to release another hormone that travels via the bloodstream to the adrenal glands atop the kidneys, where it tells the glands to release cortisol into the blood. Cortisol is also released when you exercise too much or work too far beyond your capacity, such that your body or brain becomes “stressed out”. Cortisol and adrenaline together give rise to the feeling of stress and affect every organ. They increase blood pressure so that you get enough oxygen. Cortisol makes extra glucose and fats available to your body, especially your muscles and your brain, from which your cells can derive energy. With extra energy, you are able to submit your term paper before the deadline hits. For your body, illness is caused by stress, but can also be managed by the same system. Cortisol can boost the immune system in response to acute stress so that it can defend against a pathogen, or aid in wound healing. It’s important to remember that you do need cortisol to live a healthy life. The functioning of many organs—the brain, muscles, and immune cells, just to name a few—depend to some extent on cortisol. You need cortisol to stay active during the day. Its levels fluctuate throughout the day: higher in the morning, giving you a boost to wake up, and lower at night when it’s time for bed. However, just like everything else in the universe, striking a balance is important. Momentary stress can be beneficial, giving you a boost to complete the task at hand. Even so, we all face some stressors that we simply can’t avoid, and the stress persists: war, unemployment, poverty, debt, and grief. This is what many in the medical field call chronic stress. In such a case, the constant activation of your HPA axis and increased cortisol levels can disrupt the body’s normal functioning. Sustained cortisol levels can hamper the way insulin works in the body. Cortisol raises the amount of sugar in your blood, giving you higher blood sugar levels. Insulin then decreases blood sugar levels by getting cells to store the glucose for later use. If cortisol-induced high blood sugar levels remain sustained for a long time, it can hamper how well insulin can do its job, and eventually throw off how your cells use sugars and fats. This could lead to Type 2 diabetes. Cortisol could also be the reason you’re gaining weight. There is evidence that chronic stress influences the way the body stores fat. Such links are mainly correlations, but research is ongoing. A large population-based study on 2,526 men and women measured hair cortisol levels and correlated it with instances of obesity. The study showed that chronic levels of stress were positively correlated with obesity. Another way cortisol might impact your weight is by influencing how you eat. Have you ever felt like downing a bucket of ice cream or devouring a full pizza after a long hard day? Science calls this the ‘Comfort food hypothesis’. First, cortisol controls insulin levels, which causes your blood sugar to drop. This makes you crave sweet or calorie-rich foods. Second, higher cortisol levels activate the amygdala, which makes you engage in pleasurable or compulsive activities. Binging on junk food is a common guilty pleasure for most people. Ultimately, the elevated cortisol drives these fat deposits to accumulate in the abdomen. So, the fat around your belly—also known as visceral fat—could be the result of excess stress (or cortisol) in your body. If you’ve ever gotten sick after a stressful exam week, you know that cortisol affects the immune system. Over long periods of sustained stress, cortisol prevents certain immune cells from dividing so that they can tackle a pathogen, especially viruses. This is what may be leading to your cold. Cortisol also increases something called inflammation in your body. Your tissues get red, swollen, and begin to hurt, like how wound tissue gets inflamed. This is a part of the immune system’s defense. However, inflammation over long periods is bad. It prevents the body’s cells from healing and regenerating. This causes a host of issues in the body, especially in your gut, the lining of which becomes inflamed, affecting how you digest your food. By extension, it also affects the health of your gut bacteria. Inflammation has been linked to a host of other diseases, such as heart disease and atherosclerosis—where fat deposits inside the blood vessels restrict blood flow to that area—diabetes, and even aging. Stress also directly affects your brain's functioning. Chronic stress can rewire your brain, removing old connections and creating new ones that are finely tuned to a particular stressful event. This especially affects how you remember things, and there is even evidence that the part of your brain that forms long-term memory, the hippocampus, shrinks under the strain of long-term stress. Beyond memory, the various stress hormones and inflammation can disrupt the brain’s functioning. This can lead to a broader impact on mood, cognition and brain health, and also influences behaviors like concentration, decision-making, and social interaction. Cortisol heavily affects sleep, and a dysregulated amount of cortisol can lead to poor sleep, which further worsens brain health. This all links chronic stress to developing depression, anxiety, addictions and an increased risk of Alzheimer’s disease in some people. So, is it all doom and gloom? No. Even if you can’t eliminate what’s stressing you out, you can learn to respond to it differently. The first is pretty common advice: exercise, meditate, take time for yourself doing things you enjoy, stay hydrated, and try to slow down your breathing. There is evidence that these activities dampen the effects of cortisol and stress on the body. Second, changing your relationship with the stressor can also help. Looking at what’s stressing you out and trying to change your perspective on it could help you feel more motivated to work through the stress. A mental health specialist can certainly help with this. Being stressed all the time, around the clock, isn’t normal, and shouldn’t be normalized either. Yes, everyone will feel stressed sometimes, but if it persists, it may be time for us and society to find a healthier balance.