Researchers Say Stress and Disease Are Likely Linked

Newswise — A new commentary in the Oct. 10 edition of the Journal of the American Medical Association explores whether psychological stress leads to disease and concludes that the link is likely.

The authors, who say consistent results across different kinds of studies suggest that stress plays a causal role in disease, looked at four diseases.

"The evidence from studies of depression and heart disease is most convincing. The HIV/AIDS data are a little weaker. The evidence for stress playing a role in cancer isn't all that good, even though there is supporting evidence from studies of animals," said lead author Sheldon Cohen.

Cohen and colleagues want more time, thought and dollars invested to explore whether interventions designed to reduce stress influence health. "The existing evidence linking stress to health is impressive," said Cohen, a psychology professor at Carnegie Mellon University. "What we need now is to find out what actually works to reduce stress," he added. "After that we'd like to see randomized controlled trials to determine if these stress-reducing strategies translate to less disease."

The commentators are all psychologists who study the interplay of biology and behavior on the body.

Cohen says it would be unethical to expose someone to ongoing stress that might cause them permanent harm, so gold-standard evidence from randomized experimental studies is not available. Still, there is convincing confirmation from prospective cohort studies, natural experiments, animal studies and brief laboratory tests on humans.

Cohen says the evidence adds up.

In studies of people exposed to brief, acute stress, researchers have documented changes in the way the body functions.

"That approach looks for the effect of stress on body systems related to disease — things like heart rate, blood pressure or changes in immune function — but we don't necessarily know that such changes would lead to disease," Cohen said.

Researchers have also noted associations between stress and disease in prospective studies. In those investigations, the stress levels of participants are measured; then investigators follow them to see if the participant groups who experienced the most stress are also the people with develop the highest rates of death and disease.

"The problem with that approach is there could be environmental or personality characteristics that influence both why a person is stressed and why they developed a disease," Cohen said.

In natural experiments, investigators track the health and death rates of people who experience stressors that are beyond their control (such as death in the family or a natural disaster). Since the subjects do not cause the stressful event, these studies are not subject to the alternative explanations that plague prospective studies.

Repeated, sustained stress could throw off everything from metabolism to resting heart rate to the body's response to infection and inflammatory insults, Cohen and colleagues write.

Stress might also increase the risk of disease because, "stressed people smoke more and sleep less; they don't have healthy diets; they exercise less," Cohen said.

Michael Irwin is a physician who studies the interaction of the brain, behavior and immunity. He echoes the call for more research on stress and diseases.

"This suggestion is critical as most of the data are correlations. Intervention studies are needed to show that stress amelioration impacts psychological and physical health outcomes. Randomized controlled trials are the 'backbone' of evidenced-based medicine and are needed to change how doctors counsel their patients," said Irwin, a professor at the University of California, Los Angeles.

Both Cohen and Irwin have observed changing attitudes about the influence of stress on health.

"My experience with doctors is that they do believe in the association between stress and disease, and they tell their patients to try and reduce their stress," Cohen said.

JAMA. Journal of the American Medical Association. Contact Media Relations at (312) 464-JAMA (5262) or [email protected] Cohen, S. et al. Psychological stress and disease. JAMA 298(14), 2007.