A 46-year-old woman diagnosed with breast cancer had one burning question at the beginning of our meeting: is stress related to cancer? She was in the midst of a gut-wrenching separation from her husband. She was juggling work, finances, responsibilities, child care, and in the midst of all this, had been struck by breast cancer. Had she unleashed her tumor through stress?
The quick, if unsatisfying, answer is that we don't know. Five years ago, I would have been less agnostic. Most likely, I would have said: "stress certainly can exacerbate the psychic symptoms that accompany cancer — anxiety, fear, depression, guilt. But to blame cancer on stress is to enter a cycle of blame and victimhood that can be debilitating. Cancer patients often need to summon incredible reservoirs of resilience, and stress can deplete that reservoir in some and activate it in others. And stress, of course, can enable behaviors that are cancer-linked, such as smoking. But the role of stress in directly causing cancer remains speculative.
Recently, I've begun to change the way that I think — in part, because of an astonishing experiment performed recently in mice. In this experiment, one group of mice bearing tumors were kept in "stimulating environments" — with other mice and with toys and mazes. The other group was maintained in a "normal" environment, the standard cage in a laboratory (which, while designed to be quite comfortable for mice, does not "stimulate" them). The surprising result is that mice in the stimulated environment developed smaller tumors, and occasionally developed tumors that did not grow as aggressively. When the reasons behind this difference were analyzed, the researchers could track it down to a hormone called leptin, which plays a role in metabolism, growth, fat regulation and — you guessed it — stress.
This is a mouse experiment in an artificial laboratory setting. It has been criticized by scientists who claim that prior work has never revealed such an obvious link. And it's impossible to generalize it to humans. But it allows us to begin to address the link between cancer and stress in a more mechanistic, rigorous manner. That is a crucial advance.