The use of psychiatric drugs on the battlefield has not been scientifically studied, and some say the practice carries risks.
"The black box on the label talks about side effects like suicide, poor judgment," retired Army psychologist Bart Billings warned. "It's really not a good idea to put people in a battle situation where the side effects of the medications they're taking could be suicide -- when they're carrying weapons."
As a psychiatrist in Kuwait during the first Gulf War, Ragan saw a vastly different military opinion of psychiatric medications. "Clearly, in 1990, if someone was on antidepressant medication, we sent them back to the United States."
The Army has 200 mental health professionals in Iraq to treat soldiers and monitor medications. This number has remained constant since the start of the war, even as the number of troops has increased.
Former Marine Cpl. Michael Cataldi, an Iraq war veteran, remembers the dark days that followed his first deployment.
"I was taking anti-psychotics, narcotics for pain and drinking at least 30 beers a night," he said.
He came home to Camp Pendleton, Calif., haunted by the horrors of war, including a helicopter crash that killed 30 fellow Marines.
"I saw a Marine Corps sergeant who had the majority of the top of his head missing, and he had the look of a scream on his face," Cataldi recounted. "And that stuck with me, and it still sticks with me."
Cataldi said he went to see a military psychiatrist who brushed aside his concerns. "I tell them, `I'm having nightmares. I feel like I'm having out-of-body experiences. I feel like I'm watching myself in a movie. I'm losing memory, coordination.' This whole time he said, `You're not feeling that way.' Exact words: `No, you're not.'"
Cataldi was prescribed several psychiatric medications and deployed to Iraq for a second tour of duty.
When asked for comment, Marine public affairs officer Cpt. Carl Redding told ABC News that Cataldi's records were "private and not releasable." Redding continued, "Marines with a psychiatric disorder in remission or those whose residual symptoms do not impair their duties may be considered for deployment."
Cataldi's wife, Monica Cataldi, believes the decision was wrong. "In my opinion, anybody who has to be on medication just to function, just to do their job, shouldn't go to Iraq."
A month into his second tour in Iraq, Cataldi said he ran out of his psychiatric medication.
"I went cold turkey on a narcotic in a combat zone," Cataldi said. "I woke up lying in the dirt in the middle of the night. I don't remember how I got there, with my rifle buried next to me."
"I wasn't mentally safe. I was a liability. I could have got someone hurt," Cataldi said.
Redding emphasized the military's focus on mental health. "Providing proper mental health care and assessing mental fitness to deploy are of the highest importance to Marine leaders."
Last fall, Sgt. Chad Barrett stood before an Army medical evaluation board in Fort Carson, Colo., and asked to return to Iraq, even though his medical record included a PTSD diagnosis, a suicide attempt and a commander's recommendation that he be "removed from the United States Army and receive the treatment he needs."
On Christmas Day last year, the Army sent Barrett to Iraq for the third time. He never came home.