The lethal shooting spree at a US Army base Thursday dealt a blow to an American military already under severe strain from years of war in Iraq and Afghanistan and plagued by a rise in suicides and depression.

Revelations that an Army psychiatrist had allegedly opened fire on fellow soldiers at Fort Hood in Texas came as a shock for an organization that likes to portray itself as a family.

The rampage occurs at a time of stress for the armed services burdened by two wars, with commanders struggling to ease the effect of repeated combat tours on troops and their families.

Suicides in the Army hit a record level last year, with at least 128 taking their lives, and are on track to set a new high this year -- surpassing the rate among the wider civilian population.

US commanders believe repeated deployments to Iraq and Afghanistan have played a role in the spike in suicides, as well a surge in post-traumatic stress and depression.

General Peter Chiarelli, Army vice chief of staff, has called post-traumatic stress disorder (PTSD) -- a painful mixture of anxiety and depression -- one of the "signature wounds of the war," and appealed to commanders to take it seriously.

"I want to change the stigma linked to these wounds," Chiarelli said of PTSD and traumatic brain injury.

"These are not phantom issues made up by weak soldiers. They are as real as if you fell and broke your leg or lost an arm," he told an audience last month.

Cases of both post-traumatic stress and traumatic brain injury have grown from 38 percent to 58 percent since August 2008, among soldiers stationed in Iraq and Afghanistan, according to the US Army.

And about 30 percent of soldiers deployed will likely have some form of post-traumatic stress, Chiarelli said.

The top US military officer, Admiral Mike Mullen, speaks often of his concern over suicide and post-traumatic stress, saying the Pentagon is still working to understand how to cope with the problem.

Mullen said on Wednesday that he has heard soldiers are often reluctant to report their symptoms and ask for help, fearing it could damage their careers.

"So we've just got to break that down and make it acceptable to ask for help in what is, by and large, something that is a temporary condition that, again, if it's addressed quickly, its effects can be greatly minimized," he said.

At events at Army bases, spouses sometimes speak with anger and an air of desperation, telling officials their husbands are preparing for their fifth or sixth successive combat tour and have little time at home before their training resumes and another deployment begins.

Retired officers had warned that the Army was at breaking point after a "surge" of US forces into Iraq in 2007. But commanders believe they have begun easing the strain -- increasing the time soldiers spend at home between tours.

The mission in Afghanistan, now entering its ninth year, and the controversial Iraq war have left political scars on the wider society as well, causing bitter divisions among Americans over the country's place in the world.

The controversial wars may have even played a role in the mind of the shooter, according to one colleague of Major Nidal Malik Hasan, the suspected gunman.

Colonel Terry Lee alleged the officer had expressed dismay over the US military's presence in Iraq and Afghanistan.

"He was hoping that President Obama would pull troops out ... when things weren’t going that way he became more agitated, more frustrated with the conflicts over there," Lee told Fox News channel's "Fox Report."

Lee added that "he made his views well known about how he felt about the US involvement in Iraq and Afghanistan."

But a cousin of the suspect said Hasan had been the target of harassment because of his "Middle Eastern ethnicity," even though he grew up in the United States. (By Dan De Luce/ AFP)