Post-traumatic stress disorder (PTSD) may be linked to type 2 diabetes.

Researchers from the Mailman School of Public Health at Columbia University and Harvard School of Public Health found that women with PTSD are nearly twice as likely to develop type 2 diabetes compared with women who don't have the anxiety disorder.

"When we are under stress we are more likely to get sick, but women with PTSD are in this extreme stress response a lot of the time," study author Karestan Koenen, told Time.

For the study, researchers analyzed survey data collected between 1989 and 2011 from nearly 50,000 women enrolled in the Nurses Health Study II.

They found a dose-response relationship: the greater the number and severity of PTSD symptoms, the greater a woman's risk of type 2 diabetes. Four percent of the nurses reported the highest number of PTSD symptoms. By age 60, nearly 12 percent of women with the highest number of PTSD symptoms had developed type 2 diabetes, whereas fewer than 7 percent of women with no trauma exposure had diabetes.

Antidepressant use and elevated body mass index accounted for nearly half of the increased risk of type 2 diabetes, or 34 and 14 percent, respectively. On the other hand, smoking, diet quality, alcohol intake, and physical activity did not explain the association.

One in nine women will have PTSD at sometime over the course of her lifetime--twice the rate of men. Women are also more likely to experience extreme traumatic events like rape that carry a high risk for the disorder.

"Not only is PTSD devastating to mental health, but it affects physical health too, raising risk for cardiovascular disease, diabetes, and obesity," said Karestan C. Koenen, senior author of the study.

The study builds on past findings by the researchers, including a 2013 study that reported a link between PTSD and obesity. Other research has shown a link between mental health issues like anxiety, social phobia, and agoraphobia and type 2 diabetes.

The findings are detailed in the journal JAMA Psychiatry.