http://psychcentral.com/news/2015/08/17/ptsd-does-not-increase-risk-of-cancer/90973.html
The association between stress and cancer has been discussed in scientific literature for more than 70 years. Despite plausible theories that would support this association, findings from clinical research have been mixed.
Researchers compared the rate of various cancer diagnoses among people with PTSD with the standardized cancer rate from the general population in the same time period using data from the Danish national medical and social registers. They found PTSD was not associated with an increased risk for cancer.
“The general public may have a perception that stress contributes to cancer occurrence and given the ubiquity of PTSD and cancer and their costs to individuals and society, any observed associations could have meaningful public health implications,” explained corresponding author Jaimie L. Gradus, DSc, MPH, an epidemiologist at the National Center for PTSD.
“This study, however, provided no evidence that a severe chronic stress disorder such as PTSD is associated with cancer incidence.