“It’s hard to show causality because there are so many factors that go into the development of cancer — environmental (stress included), but also genetic factors and unknown factors,” says Allyson Ocean, MD, oncologist at NewYork-Presbyterian and Weill Cornell Medicine in New York City. Ditto for the range of issues that may influence the course of cancer once it has occurred. That said, experts in the field of psycho-oncology, which concerns itself with the psychological, behavioral, and social factors that may affect cancer, say that a growing body of literature suggests that stress does play a role in cancer causation and recovery. The “hits” take various forms. Some people may inherit a gene that predisposes them to cancer, such as the BRCA1 gene, which has been linked to many cancers, including breast cancer. But a cell requires more genetic hits to trigger cancer. “If, on top of that, someone has a very stressful lifestyle, or they smoke, or are very overweight; over time, those might all be additional hits to the system,” says Dr. Ocean. Under normal circumstances, the body is exquisitely primed to prevent those multiple hits from leading to cancer. “Cells are constantly mutating in the body, but many biological processes exist to keep those mutating cells from turning into tumors,” says Lorenzo Cohen, PhD, director of the Integrative Medicine Program at MD Anderson Cancer Center in Houston. One of those processes is performed by the immune system. “Typically, the immune system is constantly surveying the body, on alert to kill invading viruses or mutating cells, a process known as ‘cell-mediated immunity,” Dr. Cohen says. When the body is under chronic stress, that safeguarding process may become less dependable. “It’s pretty clear that chronic stress disrupts the immune system, making us vulnerable to everything from a cold or flu to the uncontrolled growth of mutated cells,” says Cohen, who with his wife, Allison Jeffries, master of education, coauthored the book Anti Cancer Living: Transform Your Life and Health With the Mix of Six.
More Studies Suggest a Chronic Stress–Cancer Connection
It’s easier to see this chronic stress–cancer connection in animals than it is in human beings, mainly because scientists are able to induce both stress and cancer in their animal subjects (something they can’t ethically do in people). “We’ve shown that stress can cause cancer to metastasize in animals,” says Cohen. “For instance, a study published in December 2017 in the journal Cancer Cell found that if you put mice genetically predisposed to develop pancreatic cancer in an isolated, deprived environment separate from other mice, their tumors grow faster than in the same breed of mouse raised in normal housing.” Conversely, the researchers found that mice with pancreatic cancer that were given beta-blockers — drugs that block the release of the stress response and hormones, including adrenaline — in addition to chemotherapy survived longer than mice given only chemotherapy. “When you block the stress hormones with a drug, you can short-circuit their tumor-enhancing effects,” says Cohen. Indeed, when researchers who conducted the pancreatic mouse study looked at 631 patients with advanced pancreatic cancer who had surgery to treat their condition between 2002 and 2013, they found that those who were on a form of beta-blockers that interact with a large number of targets in the body lived about two thirds longer than those who weren’t taking beta-blockers or were taking a form that affects only a limited number of targets. One small human study, published in May 2018 in the journal Cancer, also appears to bear out the theory that stress may worsen disease. The study, which followed 96 patients with chronic lymphocytic leukemia (CLL), found that those who felt more stress and anxiety about about their condition also had a higher volume of cancer cells in their blood and higher blood levels of markers for advanced disease. The results held true even after the researchers controlled for other factors, such as gender, prior treatment, and carrying a genetic marker for the disease. “The current results indicate that stress is related to immune and inflammatory processes that contribute to cancer cell proliferation and survival,” wrote lead author Barbara L. Anderson, PhD, professor of psychology at The Ohio State University in Columbus, along with her coauthors. “It’s more evidence of the importance of managing stress in cancer patients,” said Dr. Anderson, in a release issued by her institution. RELATED: Everything You Ever Wanted to Know About Stress — Including How to Manage It
Stress Hormones Trigger Inflammation Linked to Cancer
When you’re experiencing acute or chronic stress, the body is flooded with what’s known as the stress-response hormones — epinephrine, norepinephrine, and cortisol, which can suppress the immune system’s response to mutated cells. The trouble occurs when you’re under chronic stress — that is, prolonged, unremitting — or when you experience acute stress several times a day over a period of time. Your body is then constantly being flooded with these stress hormones. Some research seems to buttress the stress-inflammation-cancer connection. A Canadian study published in November 2017 in the journal Frontiers in Oncology, for example, included work history interviews with nearly 2,000 men, age 75 or younger, who were newly diagnosed with prostate cancer, and approximately the same number of matched controls. They found that those men who reported having had at least one stressful job over the course of their lifetime were more likely to develop prostate cancer before age 65. The average age of diagnosis is about 66, according to The American Cancer Society. (Other studies attempting to link work stress and cancer risk have yielded conflicting results.) There’s another way in which the stress hormones might promote cancer: Norepinephrine may bind with beta receptors that live on the surface of some tumor cells, causing them to proliferate. “Norepinephrine can fuel a tumor’s ability to form new blood vessels,” Cohen says. “New data shows that stress hormones might also increase nerve growth and density at the tumor site, which are associated with worse outcomes in people.” RELATED: How Stress Affects Your Body, From Your Brain to Your Digestive System
More Stress Means Unhealthful Habits That Contribute to Cancer Mutations
In a kind of double whammy, people who are stressed-out are less likely to exercise and eat healthfully. In fact, unhealthful eating (think sugar and fat) may be triggered by stress-induced hormones and other chemicals flooding the body. Being overweight or obese is responsible for approximately 8 percent of all cancers, according to the American Cancer Society. Chronic stress is also likely to induce us to take up cancer promoting habits, such as smoking and excessive drinking. “It leads to lifestyle changes that are pro-inflammatory and pro-carcinogenic,” says Ocean. “Keep these habits up for a long time and your risk of developing cancer goes up, too.”
The Stress and Cancer: What Can You Do About It?
“At the end of the day, all you can do is to try and create as inhospitable a terrain for cancer as possible, so that regardless of the triggers, the cancer cells don’t grow,” says Cohen. It makes sense, for instance, to handle high-stress times with healthful habits that not only reduce your agita, but also lower your risk of a host of diseases besides cancer, including diabetes, heart disease, and Alzheimer’s. Healthful habits, Ocean says, “means exercising instead of pigging out, or doing yoga rather than throwing down a few shots over the weekend.” Also crucial: “A good support network, and prioritizing what’s important and meaningful in your life,” says Cohen. “If you can figure out what you care about, you can use those core values to guide your decision-making, which makes for a less stressful, higher quality of life in anyone, with or without cancer.” Experts also recommend engaging in some kind of mind-body practice, including deep, diaphragmatic breathing for a few minutes a day. “Studies have shown this kind of breathing actually stimulates the parasympathetic nervous system,” which tends to calm the body, says Cohen. (You can tell you are doing diaphragmatic breathing correctly by putting your hand on your belly: You should feel it rise and fall as you inhale and exhale.) Ten minutes of daily meditation with a free app, such as Calm or Headspace, can be very useful, as can any practice that involves breathing and stretching (think tai chi or yoga). Finally, consciously sitting less; getting regular exercise (30 to 40 minutes five or six times a week) and sleeping for at least seven or eight hours a night are also great stress reducers, and may even have a dramatic effect on cancer and mortality. A meta-analysis published in the British Journal of Cancer looked at the link between exercise and colon cancer risk and found that the most physically active people had a 24 percent lower risk of colon cancer than those who were the least active. Studies focusing on the occurrence of breast cancer have shown similar benefits of exercise. Even patients who already have advanced cancer may benefit from stress- and inflammation-reducing activities, such as moderate exercise and yoga. One meta-analysis published in January 2018 in the International Journal of Yoga, for instance, included more than 10,000 cancer patients from 20 different countries, and found that those who practiced yoga reported fewer symptoms from treatment, such as postoperative breathing issues for lung cancer patients; better quality of life; reduced anxiety; improved sleep; and better physical and emotional health. They also showed stronger markers of immunity, such as lower markers of inflammation. “The key, really, is finding activities that you like, that you’ll be willing to do on a daily basis,” says Cohen.
