A new study published in Cancer Research reveals that women who have had six or more symptoms of posttraumatic stress disorder (PTSD) have a twofold greater risk of developing ovarian cancer compared with women who have never had any symptoms of PTSD, reports the Harvard T.H. Chan School of Public Health.

Symptoms of PTSD may include flashbacks (reliving the trauma); bad dreams; frightening thoughts; avoiding reminders of the experience; being easily startled; feeling tense or on edge; difficulty sleeping; negative thoughts about oneself and the world; and loss of interest in enjoyable activities.

Researchers at Harvard and Moffitt Cancer Center examined data from the Nurses’ Health Study II, which tracked the health of tens of thousands of women between 1989 and 2015 using  questionnaires sent every two years, as well as medical records. Each survey asked about an ovarian cancer diagnosis, which was later confirmed through medical records.

Then, in 2008, more than 54,000 study participants completed an additional questionnaire focused on lifetime traumatic events and symptoms associated with these events. Women identified the events they considered the most stressful and the year it happened and were also questioned about seven PTSD symptoms they may have experienced as a result of the event.

Women were then divided into six groups based on their responses: no trauma exposure, trauma and no PTSD symptoms, trauma and one to three symptoms, trauma and four to five symptoms, trauma and six to seven symptoms and trauma but PTSD symptoms unknown.

Their findings showed that women who had experienced trauma and six to seven PTSD symptoms in their lifetime were at a significantly higher risk of ovarian cancer than those who had never been exposed to trauma. In addition, these women were also more likely to develop the most common and aggressive forms of ovarian cancer.

Regarding the findings, Andrea Roberts, MPH, PhD, coauthor and research scientist at the Harvard T.H. Chan School of Public Health, said, “We need to understand whether successful treatment of PTSD would reduce this risk and whether other types of stress are also risk factors for ovarian cancer.”

“Ovarian cancer has been called a ‘silent killer’ because it is difficult to detect in its early stages; therefore, identifying more specifically who may be at increased risk for developing the disease is important for prevention or earlier treatment,” said coauthor Laura Kubzansky, PhD, a professor of social and behavioral Sciences at the Harvard T.H. Chan School.

Click here to learn how PTSD affects most people living with cancer.