Why are the study results inconsistent?
It is difficult to separate stress from other physical or emotional factors when examining cancer risk (3, 4). For example, certain behaviors, such as smoking and using alcohol, and biological factors, such as growing older, becoming overweight, and having a family history of cancer, are common risk factors for cancer. Researchers may have difficulty controlling the presence of these factors in the study group or separating the effects of stress from the effects of these other factors (3). In some cases, the number of people in the study, length of follow-up, or analysis used is insufficient to rule out the role of chance (4). Also, studies may not always take into account that cancer is not a homogeneous (uniform in nature) disease. • How does stress affect people who have cancer? Studies have indicated that stress can affect tumor growth and spread, but the precise biological mechanisms underlying these effects are not well understood. Scientists have suggested that the effects of st
