A new study from a researcher at Brown University found the number of US troops who committed suicide since 2001 is beyond 30,000, and might even be higher.

The study found that the US global war on terror, unleashed in the aftermath of the terror attacks of Sept. 11, 2001, has led to 30,177 suicides by troops, either while enlisted or after they served.

By comparison, the study's author, Thomas Howard Suitt, points out that there have only been 7,057 actual combat deaths in the US military since that time.

The study notes that suicides might be higher since the Veterans Administration, which tracks suicides among its ranks, does not track all those who serve as military reservists and National Guard troops, who are often pressed into service in emergencies, as during the US Capitol riot in January.

And the study said even as war operations in Afghanistan are winding down, suicide rates among troops have been rising in recent years.

US combat deaths have gone down "considerably" since 2007 but the number of troop suicides peaked in 2012. And the last three years have seen the worst consecutive, year-to-year suicide rates among active troops since 2001.

As for the reason, Suitt says there is no one cause driving suicides, rather it is "like piecing together a puzzle we can only identify through hindsight."

But he does point to the increased use of improvised explosive devices, or IEDs, that have caused a significant number of traumatic brain injuries.

He also notes that medical advances have allowed military members to return to the battlefield, even with brain injuries that can lead to suicides.

Suitt cited the story of Army Sgt. Dominic McDaniel whose job was to protect his unit.

An IED explosion in 2005 left McDaniel with a traumatic brain injury, a discharge from the army and terrible guilt for unit members who were also injured.

McDaniel, the study noted, was treated for depression and suicidal thoughts. But he also reported that while nine of the troops wound up dying in combat, another 15 died by suicide.

According to the study, high suicide rates are "caused by multiple factors, some inherent to fighting in a war and others unique to America’s 'war on terror' framework."

"Partially, they are due to risks common to fighting any war: high exposure to trauma, stress, military culture and training, continued access to guns, and the difficulty of reintegrating into civilian life," it said./aa