BELLMORE, New York (CNN) -- Walking through a crowded shopping mall can bring back memories of war. The shifting crowds, the jostle of passers-by and the din can all trigger Army Sgt. Kristofer Goldsmith's post-traumatic stress disorder.

Upon finishing high school, Kris Goldsmith fulfilled his dream of enlisting in the Army. He was sent to Iraq.

"You get used to scanning what everybody's doing. Your brain just starts working so fast and it's purely instinctual because you want to know what everyone's intent is around you," said Goldsmith, who served four years in active duty.

"You want to know if anyone has the intent to harm you or the capabilities to harm you."

That hyper-vigilance is one common symptom of post-traumatic stress disorder. PTSD, an anxiety disorder, can develop after a terrifying or life-threatening event, or a series of events causing extreme stress.

It's a complex disorder that displays myriad symptoms. People may become more depressed, aggressive, or emotionally detached. For Goldsmith, the chest-tightening anxiety attacks and trouble sleeping he experienced after returning from Iraq in 2005 indicated he was suffering from PTSD.

"With PTSD comes anxiety problems, depression problems ... I get flashes of rage, which goes hand in hand with alcoholism I've been fighting since I got back from Iraq," Goldsmith said. Dr Gupta: Watch more on Kris Goldsmith's war experience »

As more troops return from the battlefield, the U.S. military faces a burgeoning dilemma of diagnosing and treating PTSD.

According to the latest Pentagon study, published in 2004, about one in six veterans of the wars in Iraq and Afghanistan suffers from PTSD, depression or anxiety. Learn more about PTSD

A more recent RAND Corp. study, released in April this year, found that nearly 20 percent -- or one in five returning war veterans -- reported symptoms of post-traumatic stress disorder or major depression. But, only slightly more than half of them sought treatment, the study found.

That compares with a prevalence of 4 percent for the general U.S. population, according to a 2005 study in the Archives of General Psychiatry.

As soon as he graduated from high school, Goldsmith fulfilled his childhood dream of enlisting in the Army. After his first duty station at Fort Stewart, Georgia, he and the rest of the 3rd Infantry Division deployed to Iraq. His Battalion occupied Sadr City in January 2005.

Carrying the rank of private at the time, Goldsmith had trained as a forward observer in charge of directing artillery. But once he set foot in Iraq, his job duties shifted.

At the time, radical Shiite cleric Muqtada al-Sadr had ordered his Mehdi Army militia to observe a cease-fire, so gun and mortar fire were infrequent. Instead, Goldsmith was charged with documenting everything his platoon encountered.

At first, he was reporting on the sewage, water, electrical and trash systems in the sprawling Baghdad slum of Sadr City. But he soon found himself documenting Iraqi-on-Iraqi violence instead.

"There started to be a lot of murders in Sadr City. I was a 19-year-old kid taking pictures of mutilated men, women and boys and little girls. Those are the type of images that never really go away," he recalled.

In late 2005, Goldsmith returned from Iraq. He found himself profoundly changed: drinking heavily every day, sleeping too much or too little, displaying an uncontrollable temper.

Violence and physical fights became a regular part of going out with friends.

He remembers choking someone into unconsciousness at a party. "Without saying a word, without warning, I wrapped my arms around this kid's neck and I choked him until he stopped breathing....

"I was covered in my blood and his from rolling around in broken glass as I was strangling him. And I mean that's not who I was before I deployed." Goldsmith's personal life was spinning out of control.

Back from the Battle Anderson Cooper and MTV shine a light on issues facing young veterans. A special hour on CNN.

Sat & Sun, 8 p.m. ET AC360 »

All the while, Goldsmith's military career was flourishing. He received the Army Commendation Medal for his service in Iraq. He was promoted from private to sergeant in May 2006. But he looked forward to May 2007 and the end of his Army contract as a chance to recover and get back to normal.

"I just wanted to get out of the Army, and I figured all my problems would go away once I got out of the service," he said.

But his breaking point came when his unit was given "stop-loss" orders in early 2007. Under stop-loss, military personnel are forced to stay beyond their volunteer commitments.

"Those stop-loss orders were saying that I was going to deploy to Iraq the same week that I was supposed to be getting out of the Army," Goldsmith said.

The stop-loss set in motion an unimaginable set of events for Goldsmith. In March 2007, he went to the Winn Army Community Hospital at Fort Stewart with what he believed to be a heart attack.

After cardiac testing, doctors said it was most likely a panic attack and directed him to the behavioral health clinic on base. That same day, doctors told Goldsmith he had an "adjustment disorder with disturbance of emotions and conduct."

He was told to attend group therapy sessions and given an appointment with a psychiatrist. He was found to have chronic severe depression, prescribed the anti-depressant Celexa and cleared for duty.

Goldsmith said he felt helpless and out of options.

Health Library MayoClinic.com: Post-traumatic stress disorder (PTSD)

MayoClinic.com: Post-traumatic stress disorder (PTSD) MayoClinic.com: Suicide: Understand causes, signs and prevention

"The night before I was supposed to deploy to Iraq on Memorial Day of 2007, I tried to take my fate into my own hands. What I wanted to do was make the issue of stop-loss something that people talk about and give people reason to fight against it because I had felt like my entire life had just been raped of every ounce of freedom and liberty that I had thought I was joining the Army to protect," Goldsmith said.

"So I took a black Sharpie magic marker and I wrote across my arms 'Stop-loss killed me. End stop-loss now.' I took my half bottle of Percocet and ... a liter and half a bottle of vodka and downed the Percocet and I chased it with the vodka and drank until I couldn't drink anymore."

To his surprise, Goldsmith survived the suicide attempt. His unit deployed to Iraq without him and he was discharged months later. Now 23, he lives with his parents in Long Island, New York.

His post-traumatic stress disorder was diagnosed months after his homecoming at a Veterans Affairs Hospital. He receives $700 in disability every month.

These days, Goldsmith spends much of his time working with veterans' rights groups and in the peace and anti-war movement. Earlier this year, he testified before Congress' Out of Iraq Caucus as a member of the organization "Iraq Veterans Against the War."

"I don't think that my 18-year old self would recognize who I am today. At the age of 18, I thought that I was going to be a career soldier.... I never imagined speaking out."

All About Post-Traumatic Stress Disorder • Armed Forces • Iraq War