The study looked at more than 2,300 pairs of men and woman deployed to Iraq or Afghanistan and matched based on a number of variables — such as combat exposure, age, race, military occupation, marital status and pay grade. The researchers followed the pairs for an average of seven years and found that 6.7 percent of women and 6.1 percent of men developed PTSD.
The researchers said the difference was not statistically significant and that there wasn't a difference in severity for those who did develop the disorder.
Previous studies have been a bit of a mixed bag in terms of PTSD rates among military women, but some studies have reported that women are at higher risk of PTSD. That's commonly been used as an argument against letting women fight alongside male peers on the front lines.
But those studies focus on military populations as a whole, regardless of the individuals' previous cases of PTSD. Women in the general civilian population are also more likely to suffer interpersonal trauma — such as sexual assault — through people who they're familiar with.
"We were able to adjust for a number of things that people were unable to adjust for in the past," said Shira Maguen, an author of the study and a mental health director of the the San Francisco VA Medical Center. "This issue of exposure is extremely important. We're looking at different types of exposure."
In this study, researchers only looked at men and women who had no previous indications of PTSD, and found there's no difference in newly developed cases of the disorder. That's also why this study is reporting a lower PTSD rate among veterans than earlier estimates, which put the disorder at as high as 20 percent for returning Iraq and Afghanistan veterans.
Keeping track of the PTSD is important, as an estimated 2.7 million American veterans of the Iraq and Afghanistan wars are affected by it. The disorder is triggered by traumatic events, with symptoms including flashbacks, nightmares, bouts of anger and severe anxiety. For most people, the symptoms go away over time, but for others, they are a difficult hurdle in living a normal life.
While it can be treated with the use of antidepressant medications and psychotherapy, only half of veterans seek treatment — and of those, only half get "minimally adequate care," according to a study by the Rand Corp.
The study came out at a time of heightened interest in women's future role in the military combat. In early 2013, then-Defense Secretary Leon Panetta rescinded the ban on women in combat, giving the different branches of the military until January 2016 to request exceptions to the new policy.
The move sparked opposition to bringing women into the most demanding positions in the front lines. Opponents argue that female physiques are not built as ready for combat as are men's, so including them would put the rest of a troop at greater risk. They cite studies that show women have higher rates of injury than men.
Last week, two women graduated from the Army's rigorous Ranger School, becoming the first ever to break that gender barrier. Although both failed the initial phase of Ranger School, they persevered to become the first women ever to wear the elite Ranger Tab on their uniforms. Their story has lent energy to the movement for expansion of women's roles in the military.
"(Our study) bodes very well for women not only in leadership but also women in lower ranks," Maguen said. "Women have been doing this for many years now. What we should be focusing on is abilities and readiness."