How Stress Works
Stress, in its simplest term, is the human body’s reaction to adversity, which also involves a mental response. When a person feels stress – whether physical or mental – it activates the fight-or-flight response.
The body’s stress hormone system activates a corticotrophin-releasing hormone that’s part of the hypothalamus in the brain, a small part of the brain responsible for controlling the nervous system. The hypothalamus tells the pituitary gland to release adrenal cortical-stimulating hormone into the bloodstream. That, in turn, tells the adrenal gland to release adrenaline. We’re all familiar with this hormone, which increases heart rate, contracts blood vessels and basically gets you ready to fight or run away. Adrenaline, in turn, triggers the release of cortisol, which also helps get your body ready for “fight or flight.”
There is evidence that the stress response, at very high or very low levels of stress, has been linked to the worsening and onset of some diseases, including cancer. However, a moderate level of stress can actually help fight disease and is useful for the body.
Illustration by Pete Ryan
When Dr. Kathy Hegadoren was diagnosed with breast cancer on May 14, 2010, the nurse who researches stress at the University of Alberta was well aware of what was going on in her body, and in her mind.
“I felt blind-sided,” says Hegadoren, who holds a Canada research chair in stress-related disorders in women. “Even though I didn’t perceive myself as stressed, when I was diagnosed I had lots of behavioural evidence of stress – a hard time sleeping, a hard time concentrating at work – but I didn’t feel jittery. My mind would just wander.”
When she started her first round of cancer treatment in late July, Hegadoren just wanted to get on with it, so she could take some action over her diagnosis. “In some ways, it allows me to feel more in control, which makes you feel less stressed,” she says. “It’s about personal control. It’s a journey. You have to believe in getting up and having hope, not having your diagnosis becoming your whole life.”
A cancer diagnosis obviously causes a lot of stress, but Hegadoren says the concept of stress is very elusive for many people. “It’s so difficult to define because it has so many meanings,” says Hegadoren. “It can be used as a noun, a descriptor, a perception, a physiological and biological pathway, all of those things can be characterized as part of the stress response.”
You can’t see it, but people respond differently to stress in various circumstances and different levels of stress can be either positive, or negative. Too little stress, or too much, has been linked to the onset or worsening of certain diseases, such as heart disease, diabetes and many others.
One of two key stress hormones, cortisol, increases insulin resistance, for example, which means insulin has a harder time getting into certain cells in the body. “If you have that chronic insulin resistance, there is some evidence that chronic state of insulin resistance can increase your risk for Type 2 diabetes,” says Hegadoren.
People who have chronic stress also tend to end up with more symptoms of irritable bowel syndrome and inflammatory bowel disease, according to Dr. Donna-Marie McCafferty, an associate professor at the University of Calgary. She studies the link between irritable bowel disease and cancer, involving metabolic stress. Current research suggests a link between stress and worsening irritable bowel disease symptoms, including diarrhea, stomach cramps and other digestive problems.
Stressed-out mice
A moderate level of stress has been proven to help shrink cancerous tumour growth in lab tests and the Ohio-based researcher who conducted the tests on mice says this could have huge implications for humans. “The goal here is to start to prescribe lifestyle management as an approach to treating diseases like cancer,” says Dr. Matthew During, a professor of neuroscience at Ohio State University Medical Centre.
His team injected mice with three types of cancer – melanoma, colon and spontaneous intestinal cancer – and placed mice in two scenarios: one with mice in a large cage with toys and very low levels of the stress hormone leptin being measured, while the others were placed in a more crowded or “challenging” environments. The mice in the more challenging environments, where they had to compete with other mice and even show aggression, had slightly higher levels of the stress hormone.
Researchers found the mice’s tumours in the stimulating environment shrank by 50 per cent after three weeks and 77 per cent after six weeks. The tumours even disappeared entirely in one in five mice. At the same time, the tumours continued to grow in the mice with low stress levels. “Our studies show that a small amount of stress activates this particular pathway from the brain to fat that regulates the release of (leptin)… so if you activate that pathway – done by partial stress – it starves the tumour,” says During. The more leptin the mice produced, the smaller the tumours became.
“A certain amount of stress is healthy for you,” During says. “It’s like a U-shaped curve and if you get too much stress it is not ideal, a small amount is extremely good and then you go beyond that … excessive stress becomes distress and it’s a dysfunction.”
Some studies also link irritable bowel disease to an increased cancer risk. “However, no conclusive study demonstrates that stress management has a beneficial effect on inflammatory bowel disease,” says McCafferty. “There are a couple of (studies) which indicate that the duration and severity of inflammation in irritable bowel disease patients is linked to the development of cancer. Therefore, if stress is linked… to irritable bowel disease then, in theory, it could contribute to cancer development.”
Stress even has implications on memory. Dr. Ken Lukowiak, a University of Calgary professor who studies how stress alters memory function, agrees there is a strong link between feeling in control and how stress affects people. “What form the most stressful stimuli are those that we don’t control,” he says. “If you can’t control the stimulus, then you can predict quite highly that it’s going to be a stress stimulus in the wrong way. Some stresses are very useful and others are extremely detrimental.”
Yet, even Hans Selye, a Hungarian-born Canadian who Lukowiak calls the “father of stress research,” had a famous quote about how elusive stress is for most people, saying: “Everybody knows what stress is, but nobody really knows.”
Lukowiak describes stress as a bell-shaped curve, where you plot memory function, from poor to good, on one axis and stress level on the other axis. “At low stress, you won’t learn anything and if you are far too stressed out, you’re not going to learn anything,” says Lukowiak. “There’s an optimal level of stress that one wants to achieve. You want to always get into that sweet spot and that sweet spot is going to change dramatically, depending upon all sorts of things.”
Age and individual circumstance, for example, can greatly alter what would be considered the optimal, moderate level of stress. “It’s all in the eyes of the beholder and, even then, it’s going to change depending on your internal state,” he says.
Kathy Hegadoren knows that her mental state changed when she learned of her breast cancer diagnosis, but she credits a strong support network, personal resources and a positive outlook with helping her to achieve a balanced state, despite the presence of some understandable stress. “Stress is actually very positive and, in its most elemental way, it’s our instinct to survive,” says Hegadoren. “When we talk about disease, not only can overwhelming stress lead to chronic diseases, but it can lead to mental disorders.”
Being aware of stressors in your life is the first important step to address how you handle your body’s response and how you cope mentally. Hegadoren, meanwhile, is focused on her treatment plan and will continue her own journey, dealing with stress the best she can along the way. “I have a huge support network – a strong marriage, children who care deeply about me and lots of people that love me,” she says. “I have the luxury of having lots of things that others don’t always have.”