Stress can cause a number of physical health problems, however the evidence that it can cause cancer is weak. Some studies have shown a link between psychological factors such as stress and anxiety and an increased risk of cancer. On the other hand many studies have failed to find evidence that people who tend to be anxious or stressed are any more likely to develop cancer than people who are more relaxed. A meta-analysis study published in 2013 of work stress and cancer risk, found that work stress, measured by job strain (high demands and low control at work) was not associated with colorectal, lung, breast or prostate cancer. There does not appear to be any such thing as a cancer-prone personality.

Several explanations may account for apparent links between stress and cancer. For example, people under stress may develop behaviours such as smoking, overeating, or drinking alcohol, which are known risk factors for cancer. Likewise, someone who has a relative with cancer may have a higher risk for cancer due to genetic risk factors, not because of the stress associated with a family member’s diagnosis.

Cancer Council NSW

Main point is that there is, to date, no compelling evidence that stress causes cancer. However behaviours occasioned by stress may increase an individual’s risk of cancer.