Hundreds of thousands of troops returning from Iraq and Afghanistan will struggle with the potentially debilitating psychological effects of war.

At least 638,000 soldiers who served in Iraq and Afghanistan have been deployed more than once, according to the Department of Defense(DoD). The Army’s Mental Health Advisory Team most recent report from 2008 said that soldiers who deployed to Iraq more than once were much more likely to develop PTSD.

“The deployment tempo is just burning through these service members and their families,” said Dr. Jonathan Shay, a leading PTSD psychologist and clinician at the Department of Veterans Affairs (VA) outpatient clinic in Boston, Mass.

“They are just being chewed up and spit out and destroyed,” he said.

A 2009 study by researchers at Stanford University estimates that by 2023, roughly 40 percent of the active Army and Marines and 32 percent of the Army reserve that deployed to Operation Iraqi Freedom will develop Post Traumatic Stress Disorder (PTSD).

This is partially due to the fact that the nature of warfare in Iraq and Afghanistan differs dramatically from previous wars. The Taliban wear no uniform, and troops have difficulty determining who is the enemy, especially when under fire.

“There really isn’t a front line,” said Sonja Batten, deputy director of the Defense Centers of Excellence for Psychological Health and Traumatic Brain Injury.

“Anyone could be the enemy,” she said. “You could encounter an IED on the side of the road just as you’re doing transport from one place to another.”

Improvised explosive devices, or IED’s, are responsible for the majority of American deaths in Afghanistan, and have killed hundreds of U.S. soldiers and injured at least 20,000 since 2001, according to the DoD’s Defense and Veterans Brain Injury Center. Roughly two-thirds of soldiers wounded in action in Iraq suffered blast-related injuries, according to DoD data.

These explosions also affect soldiers who experience the blast but are not killed or seriously injured, in often unseen ways. Post Traumatic Stress Disorder (PTSD) is the most well known of many psychological injuries that can be triggered by traumatic events such as frequent IED attacks.

“About one third of the service members we’ve sent over to Iraq and Afghanistan are expected to return home with a mental health condition,” said Paul Sullivan, a veteran and executive director of Veterans for Peace, a national veteran’s advocacy group.

Roughly one in five soldiers, around 350,000, who fought in Iraq or Afghanistan is expected to develop PTSD or depression, or both, according to a 2008 RAND Corporation study called “The Invisible Wounds of War.”

The focus on PTSD has led many other psychological injuries that can result from a traumatic event to be overlooked, according to Dr. Matthew Friedman, Executive Director of the National Center for PTSD.

“Only a minority--a significant minority--maybe 15-20 percent, are going to have something that is clinically diagnosable, and that’s PTSD,” he said.

“But for most of them,” he continued, “[their problems] can wreck a marriage, they can wreck a career, they can wreck a friendship, but it might not be PTSD, it might be some [other] post-traumatic problem.”

For example, soldiers exposed to bomb blasts can also experience a traumatic brain injury (TBI), or brain damage caused by the powerful shock waves of an explosion. The dramatic rise in severe TBI since 2001 is well documented, as modern military medicine has saved the lives of thousands of soldiers suffering from head injuries that would have killed them in previous conflicts.

At least 370,000 soldiers are expected to sustain a ‘mild’ or ‘minimal’ TBI, and most don’t even know it. The Defense and Veterans Brain Injury Center estimated that 27,862 soldiers suffered some for of traumatic brain injury in 2009.

“There’s nothing minimal about it,” said Dr. Thomas Horvath, Chief of Staff of the Michael E. Debakey Veterans Affairs Medical Center in Houston. “It can be quite debilitating, in a subtle and complicated way.”

Mild TBI is a brain injury similar to a concussion or repeated concussions. But soldiers can experience one without ever hitting their heads. The shock waves smash the brain against the inside skull like in a concussion. For years, soldiers were told to shake it off and get back to work.

In the section called PTSD and TBI, Michael Jernigan, a Marine severely injured by a roadside bomb blast and diagnosed with PTSD, describes the consequences of his wounds and how strong family support and a rapid diagnosis by military medical staff guided him to the road to recovery. Jernigan eventually enrolled in college and is now a frequent blogger on The New York Times “Home Fires” blog that is designed to allow veterans to write about their experiences.

“Coping with traumatically stressful events is a seldom a solitary task and typically requires considerable amounts of assistance and support from other people,” according to the 2008 Encyclopedia of Psychological Trauma.

Many veterans are not as resilient as Jernigan and wind up as part of the growing statistic of military suicides.

In 2009, at least 328 active duty and reserve Army service members committed suicide, according to the U.S. Department of Defense. Every day the VA reports that at least 18 veterans commit suicide--more than 6,500 a year.

Experts within and without the VA say that veterans are suffering due to a scarcity of mental health professions within the military, the high psychological toll of repeated deployments, and a reluctance by affected soldiers to seek treatment.

“It could be foreseen exactly where we are today and have been for several years,” said Shay, “and still the end-strength has not been increased to permit the deployment tempo to be supported in a way that doesn’t utterly destroy the people that inhabit these institutions.”

Shay said that when he worked in the Pentagon in 2003, he tried unsuccessfully to pressure the military brass--under the influence of then Secretary of Defense Donald Rumsfeld--to increase the total number of troops.

“The people who made those kind of policy decisions,” he said, “I think they have blood on their hands.”

The dramatic rise in suicides has shocked the military into action. The DoD is trying to increase the number of mental health professionals in Iraq and Afghanistan. Currently, there is roughly one mental health professional for every 1,200 soldiers deployed overseas, according to the DoD.

The Pentagon also instituted mandatory screening for psychological injury before and after deployment, and has attempted to reduce the stigma associated with PTSD within the military. In August 2009, the DoD established a Suicide Prevention Task Force to combat military suicides, and has established a toll-free suicide hotline for veterans.

For those like Shay who predicted a rise in PTSD, TBI and other psychological injuries as a result of the Iraq and Afghanistan wars, the military’s efforts are a welcome change in policy.

“They didn’t volunteer for self-destruction,” said Shay, who is considered one of the country’s foremost scholars on the psychological impact of the Vietnam war. “They volunteered to do something useful for the country, even if it was at some risk to themselves.”

According to the National Priorities Project, a non-profit research organization that analyses federal data so that people can understand and influence how their tax dollars are spent, close to one trillion dollars has been spent on the wars in Iraq and Afghanistan. Founded in 1983, the organization looks a the impact of federal spending and policy on local, state, and national levels, to help people understand where tax-dollars are being spent and to propose alternatives. In the case of the money already spent on the current wars, the NPP estimates that more than seven million affordable housing units could have been built.