How stress shapes cancer’s course
About two millennia ago, the Greek physicians Hippocrates and Galen suggested that melancholia — depression brought on by an excess of “black bile” in the body — contributed to cancer. Since then, scores of researchers have investigated the association between cancer and the mind, with some going as far as to suggest that some people have a cancer-prone or “Type C” personality.
Most researchers now reject the idea of a cancer-prone personality. But they still haven’t settled what influence stress and other psychological factors can have on the onset and progression of cancer. More than a hundred epidemiological studies — some involving tens of thousands of people — have linked depression, low socioeconomic status and other sources of psychological stress to an increase in cancer risk, and to a worse prognosis for people who already have the disease. However, this literature is full of contradictions, especially in the first case.
In recent decades, scientists have approached the problem from another angle: experiments in cells and animals. These have revealed important mechanisms by which stress can alter tumors, says Julienne Bower, a health psychologist at UCLA who coauthored a 2023 article on the connection between the brain and the immune system in diseases, including cancer, in the Annual Review of Clinical Psychology. Such studies are showing that “psychological factors can influence aspects of actual tumor biology,” she says. On the flip side, studies in people and animals suggest that blocking the chemical signals of stress may improve cancer outcomes.
Today, a growing number of researchers think that psychological factors can influence cancer’s progression once someone has the disease. “I don’t think anyone appreciated the magnitude by which even mild stress, if it’s chronic, can have such a negative influence on cancer growth,” says Elizabeth Repasky, a cancer immunologist at the Roswell Park Comprehensive Cancer Center in Buffalo, N.Y.
