Stress and Cancer: A Complex Relationship

International Stress Awareness Day falls at the beginning  of November,  and it highlighted a common question that we  often receive at the Canadian Cancer Survivor Network (CCSN).

Even before the pandemic, stress levels were on the rise across the country. In 2022, Statistics Canada published information on the reported levels of stress for Canadians aged 12 and up. Respondents were asked if most days in their life were either “quite a bit” or “extremely” stressful.

Between 2021 and 2022, an extra 500,000 Canadians reported feeling more stress in their day-to-day lives. That equated to a 1.4 percent jump, for a total of 7.1 million Canadians feeling high levels of stress The increase was felt across all age groups.

And so, with stress and cancer rates rising, is  there a link between stress and cancer? The answer is very complicated, and not really a direct yes or no.

The Canadian Cancer Society lists this issue under the “controversies and myths” section, and claims that research has not proven a definitive cause-and-effect relationship between stress and cancer. Stress is complicated, and its effect on the body is complicated as is cancer , and as a result the research is inconclusive.

A study among Canadian men with prostate cancer found an association between the condition and workplace stress (PMID: 27923666). However, another study showed that the link was not so clear (PMID: 29181335). One five-year UK study on stress and breast cancer found there was inconsistent evidence linking stressful life events with the disease (PMID: 27418063). One study showed that stress could make dormant cancer reactivate after treatment, although a lot of other factors have to be in place for this to happen (PMID: 33268511).

Meta analyses of cancer-and-stress studies would sometimes show a link, and others would not. One of the main criticisms of these studies is that finding a measurement for stress is difficult. Most rely on the participant self-reporting how much stress they are feeling, regardless of what their body is doing in response to it. This means that many of these studies  hinge on a degree of subjectivity.

At best, the evidence points to an indirect relationship. And that’s where even more complexity starts.

First the most obvious link: People with stress may resort to stress-induced behaviors, and often these behaviors are linked to cancer. Smoking tobacco and drinking alcohol, often used as stress-management tools, are known carcinogens. Stress eating can often consist of processed foods and red meat and is often unhealthy.

Poverty in general creates a stress-and-cancer feedback loop, as Dr. Ambreen Sayani explored in one of our webinars, which you can watch here.

In addition, stress has been shown to alter hormone levels. However, while cancer tumours do react to changes in hormone levels, and some hormones do cause cancer in certain people, linking stress-specific hormone changes to cancer is far from a certainty. In addition, it’s not clear if certain hormones increase or decrease your risk of cancer, and so to say that stress-based hormone changes cause cancer is inaccurate in a lot of cases.

Finally, stress has been shown to weaken the immune system. Stress produces cortisol which, while it boosts immunity in the short-term, can also suppress your immune system if there’s too much of it. Many viruses, like HIV, HPV, and hepatitis, are known to cause cancer, and the ability of the body to fight these off will directly be hampered by stress.

In all cases, stress may not be carcinogenic, but if it is not managed properly, it can lead to things that increase your risk of getting the disease. This is a meaningful distinction, because being stressed out is not a one-way road to cancer. Eating healthy, abstaining from smoking and drinking, and having healthy outlets, like exercising, can turn stress from a cancer risk into a way to protect yourself from the condition.

So, in a sense, stress can cause cancer, but only if it’s allowed to.