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.