Does stress cause cancer?
While the opposite is certainly true -- cancer causes stress -- it's not known for sure how stress may lead to or exacerbate conditions like cancer. But it's an intriguing question among experts who are researching the potential links.
Perhaps the strongest indication that there may be a connection between stress and cancer comes from research in cell biology and biochemistry. Recent experiments have shown that certain molecules that increase in times of stress have also been linked with several diseases including cancer.
While the research is young, "inflammatory pathways activated by stress have been implicated in the development of tumors, metastasis of tumors, and resistance to chemotherapy," said Dr. Charles Raison, professor of psychiatry and behavioral sciences and director of the Behavioral Immunology Clinic at Emory University in Atlanta.
What's better-known: People who are in acute stress have been shown to have a reduction in immune function, but how that might translate into cancer in people is hard to define.
"People in high-stress occupations, such as police officers, doctors and firefighters don't have higher incidences of cancer than other members of the community," said Dr. Derek Raghavan, director of the Cleveland Clinic Taussig Cancer Center. "There is folklore that people who are grieving have a higher chance of getting cancer than others. But the data are conflicting, and carefully controlled studies do not support it."
Another viewpoint: Stress may not lead to the development of cancer, but it may affect its progression.
"Once you have cancer, then the presence of stress and stress-related states like pessimism and hopelessness are associated with the progression of cancer and decreased survival," Raison said.
Many scientists, however, disagree.
"There is virtually no connection between stress and cancer. I think it's disastrous that people are led to believe there is," said Robert Sapolsky, professor of neuroscience at Stanford University. "The right supportive setting can decrease stress and will indeed enhance the biology of how your body can deal with disease. But cancer, I think, does not fall into that category."
How Stressed Do You Feel?
What, then, is known for sure about the effects of stress? There is plenty of evidence that stress alters aspects of immune function, according to Dr. Sheldon Cohen, professor of psychology at Carnegie Mellon University. "People under higher stress are more likely to catch a cold when we expose them to a virus," he said.
Stress has also been shown to cause exacerbations of autoimmune diseases like multiple sclerosis, diabetes and rheumatoid arthritis, according to Raison.
"Even if you control for depression, stress in HIV patients is associated with more rapid progression of the illness and higher viral loads," he said.
So, the quandary is that although stress is known to have an affect on immunity, it is not yet clear how the immune system plays a role in cancer, as opposed to heart disease where the link with stress and inflammation is becoming better understood.
The definition of stress is also being looked at. There are clearly measurable stressors like the death of a loved one, losing a job or divorce. But what's more accurate, says Raison, is "perceived" stress. In other words, how stressed out do you feel?
"It turns out that perceived stress is more predictive of illnesses than how many bad things have happened to you," Raison said.
What does all this mean for cancer patients? Support groups might be the answer.
"Women with breast cancer randomly assigned to a year of supportive group therapy lived longer than control patients," said Dr. David Spiegel, professor of psychiatry and behavioral science at Stanford University and author of the groundbreaking study.
The problem is that among the subsequent trials, only half showed an increase in survival, while half show no difference.
As to whether group therapy helps cancer patients live longer, Spiegel said, "I think it's still an open question. I think it helps emotionally, and it's possible that it helps physically."
The take-home message, Speigel says, is that "it's important to acknowledge and deal with stress, whether or not it has any affect on the incidence or progression of cancer."