Editor's Note from Brian Ross: In the third year of a joint project with the nonprofit Carnegie Corporation, six leading graduate school journalism students were again selected to spend the summer working with the ABC News investigative unit.
This year's project involved an examination of whether, as happened in the wake of the Vietnam War, Iraqi war veterans were turning to drugs as a result of the trauma and pain of war.
The U.S. military maintains the percentage of soldiers abusing drugs is extremely small and has not increased as a result of Iraq.
The students' assignment was to get the unofficial side of the story from soldiers, young men of their own generation.
Today's report is the third in a series of five reports.
As more U.S. service members return home from Iraq and Afghanistan after witnessing the horrors of war, more will turn to drugs and alcohol to cope.
That's according to mental health experts who say there is a strong correlation between Post-Traumatic Stress Disorder, or PTSD, and substance abuse. PTSD is an anxiety disorder that afflicts people who have been through a traumatic event.
Dr. Phillip Ballard, a psychiatrist at Penrose-St. Francis Health Services in Colorado Springs, Colo., said he has seen a significant increase of soldiers from nearby Fort Carson seeking inpatient treatment for substance abuse.
"PTSD has as part of its core diagnosis the use of substances as self-medication for the relief of depression, anxiety, whatever feeling they may have," Ballard said. "Sometimes it's considered to be a weakness or a less than manly thing to ask for assistance or ask for help so they do the best they can do with what they have available...they use the chemicals and drugs they've used in the past to numb feelings up."
Between 30 and 50 percent of people with post-traumatic stress disorder will also abuse substances, according to Ballard.
As many as half of all PTSD patients treated in the Veterans Health Administration also have a substance abuse problem, according to the Department of Veterans Affairs' own information.
That is potentially a big concern since as many as one out of every four soldiers, or 28 percent, in combat brigade teams could be at risk for developing PTSD, according to a Department of Defense Task Force on Mental Health report from June 2007. Almost 40 percent of soldiers who have returned home report psychological symptoms, according to the report.
Col. Elspeth Ritchie, the psychiatry consultant to the U.S. Army Surgeon General, acknowledged that post-traumatic stress is a risk factor for the abuse of drugs and alcohol, but said that the Army has not been able to quantify how strongly the two are linked. The Army maintains that there has been no increase in the rate of illegal drug use among soldiers since the beginning of the wars in Iraq and Afghanistan.
ABC News was able to interview numerous U.S. service members who say they turned to drugs to help cope with their PTSD symptoms.
Gamal Awad, a former major in the U.S. Marine Corps, said he smokes marijuana to help cope with PTSD. Awad was first diagnosed with PTSD by a Marine psychiatrist after the 2001 attack on the Pentagon during which he said he picked severed limbs out of the rubble.
Despite the diagnosis and his ongoing treatment for PTSD, Awad was still deployed to Kuwait and Iraq, which he said made his condition much worse.
"I was having suicidal thoughts...I would go out on convoys with the purpose to die. I just wanted to be hit by an IED or get shot. We'd get hit with, you know, mortar rounds or rockets, I wouldn't take cover. I would just stand there," said Awad.
Awad said military doctors prescribed him a range of antidepressants and sleep medication, but he fell into a spiral of depression and misconduct that led to his discharge from the Marines. A civilian doctor then prescribed marijuana, which is legal in California for medicinal use, to treat Awad's PTSD symptoms.
"It's the one thing that's given me some sort of peace, some sort of sleep for more than three or four hours, and it's medical marijuana," Awad said.
Others like Alan Hartmann can't handle the nightmares and don't want to sleep, so they say they turn to uppers like cocaine or amphetamines.
Hartmann served as a specialist in Iraq shortly after the war started. He suffered from terrible nightmares after returning home. In one, Hartmann dreamt he was a soldier in World War II and that someone had stabbed him in the back causing his spinal fluid to leak out, according to his medical records.
Unable to handle the intense images, Hartmann abused methamphetamines to stay awake, he said. He said he went into rehab and has kicked his illegal drug habit.
"The nightmares were killing me, from being over there. The pain was so bad I didn't want to deal with it. Well, amphetamines is a really quick way to get rid of it…I got addicted for a long time, doing a lot of it," he said.
Col. Ritchie said she was unaware of cases of soldiers turning to drugs to cope with the trauma of their experiences in Iraq.
"That has not been my experience," said Col. Ritchie. "My psychiatrists and social workers who see soldiers report to me of their experiences with soldiers all the time, and none of them are seeing that particular explanation."
Col. Ritchie said in her experience, soldiers more commonly turn to drugs to recreate "the intensity, the adrenaline high" that they got during combat.
Psychological trauma and drug use, however, are nothing new for combat veterans, said Steve Holsenbeck, a former psychiatrist at Fort Carson who served in the military from 1973 until 1993. Many of this nation's homeless are veterans of previous wars who are still grappling with psychological issues from their service, he added.
"I suspect we'll see a lot of what we continue to see from Vietnam," Holsenbeck said. "I think it's going to look exactly like it looked then and like it looked after the Crimean war and after probably the battles between Spartans and Athenians. You're going to see people who are veterans, who came back; everything piled up on them; they got addicted to alcohol or drugs, lost their employment; they lost their families; they end up on the street."
Additional reporting by David Schneider and Mansi Mehan.