In the 20 years since the September 11 terror attacks, four times as many deaths among members of the military have been caused by suicide compared to those killed in action.

That’s 30,177 active duty personnel and veterans of the post-9/11 wars who have taken their own lives.

While these high suicide rates can partially be attributed to the mental health toll of participating in war—exposure to trauma, stress, access to guns, difficulty returning to civilian life after duty—there are additional factors, one of the biggest being traumatic brain injury, unique to the wars stemming from 9/11, that contribute to the rising suicide rates among military members, says Thomas “Ben” Suitt, who earlier this year earned a PhD from Boston University’s graduate program in religion, specializing in the sociology of religion in the military and social ethics.

“Among the demographic of veterans aged 18 to 34, who most likely served in post-9/11 conflicts, the suicide rate per 100,000 was 25.5 in 2005. Today, that rate is 45.9 per 100,000,” Suitt says.

While pursuing his doctorate, Suitt was studying moral injury and the role of faith in 9/11 veterans. Talking with them for his research, he was struck by their stories of trauma.

“I was looking at Veteran Affairs (VA) and Department of Defense (DoD) data, and I saw that no one had put it in terms of how bad suicide rates are getting,” Suitt says. “Rates are getting worse and worse.”

Historically, he says, data indicate that suicide rates typically go down among members of the military during wars. But military suicides have gone up during the War on Terror, meeting and surpassing the suicide rate among civilians.

Read the full article about military suicide rates by Kat McAlpine at Futurity.