Enlarge Speakes family photo Grant Speakes' father is retired lieutenant general Stephen Speakes. Both soldiers spoke about how important it is for troops to deal with mental health issues. WASHINGTON  Army Capt. Grant Speakes had lived through the worst the Iraq war has unleashed: He had heard the screams of a soldier burned to death in a roadside bomb strike, stanched the bleeding of a soldier cut down by a sniper and killed an insurgent himself. He returned home haunted by the memories. While riding in cars, he jumped when other vehicles pulled next to his. He drank too much. One night at his parents' home, his father, retired lieutenant general Stephen Speakes, found his son sitting awake at 2 a.m., rocking back and forth alone in a chair. One night he finally crumbled. "My dad had been calling, leaving messages asking why I didn't return his phone calls," Grant Speakes said. "I just broke down and told him all the stuff I was dealing with. I was crying outside Hooters on the phone in Killeen, Texas. That was a low point for me." Soldiers such as Grant Speakes, who say they killed enemy troops in combat, are at greater risk of suffering combat stress and having emotional problems, a new study shows. HYPERBARIC CHAMBER: May treat traumatic brain injury PAIN PILLS: Abuse concerns Pentagon CASUALTIES: American casualties in Iraq, Afghanistan, and beyond Those soldiers often pay a profound psychological and emotional toll, according to Shira Maguen, lead author of the study on soldiers and post-traumatic stress disorder. Of nearly 2,800 soldiers surveyed, 40% reported killing or being responsible for somebody's death in Iraq. "Those who acknowledged killing somebody in combat were more likely to have PTSD symptoms, anger, relationship problems," said Maguen, a staff psychologist at the San Francisco Veterans Affairs Medical Center. Grant Speakes is among tens of thousands of U.S. troops who say they have had some type of combat stress from their service in Iraq or Afghanistan. Of the nearly 2 million veterans, 5% to 20% have some symptoms of post-traumatic stress, according to the Joint Chiefs of Staff. Speakes, now 27, feared the stigma that he and others say exists in the military concerning those who seek help. His father says the thought of career damage to him or his sons never concerned him. "I didn't know he was worried about it," Stephen Speakes says. "It never crossed my mind. I was very worried about how best to help him." Today, he says, he's happy to have "90% of my son back." Both talked to USA TODAY about the young officer's ordeal, the stigma of mental health problems and the need for soldiers to address them. Military family Grant Speakes and his twin brother, Brennan, were born into the Army and moved from post to post as their father ascended the ranks. Later, Grant Speakes entered Texas A&M, a training ground for officers. There he met Christy Fischer. The two would marry, but not before Grant spent a harrowing year in Iraq. That year started Dec. 31, 2005, when Speakes, then a lieutenant with the 4th Brigade of the 4th Infantry Division, arrived at Forward Operating Base Falcon on the southern edge of Baghdad. Early patrols were mostly routine. They became treacherous as insurgents began using larger roadside bombs and the first of a more powerful type, explosively formed penetrators (EFPs) that can pierce even heavily armored vehicles. Speakes' unit saw heavy combat, including a battle in which he ordered the driver of his Humvee to crash it through a cinder block wall. The soldiers needed room to maneuver and shoot. "I got out of the truck and fired. I called in air support," Speakes says. The soldiers captured 10 men suspected of financing insurgent attacks. Back at the base, Speakes was spent. He would be awarded an Army Commendation medal for valor. "That night, I realized I hadn't slept in 50 hours," he says. "You've got gunpowder ... on you. So I called home. 'Hey, Dad. I think I killed a dude. At least one.' "Then I threw up. I was drinking a milkshake at the time. I'd like to pretend it was from the milkshake. But I don't think so." The cost of killing Soldiers who have killed in combat need treatment, Maguen's study says, and "may experience significant shame and/or guilt and need to know they will be allowed to explore the impact of killing in a safe and supportive environment." Acknowledging killing experiences and analyzing them may stop soldiers from the "shame, stigma and secrecy associated with taking a life in combat," Maguen's study says. "Including killing in our evaluation and treatment planning will ensure that we are providing comprehensive health care to our newly returning veterans as they face the challenges of reintegration." The toll became evident to Grant Speakes during a mid-tour leave. He visited Christy and his brother in Oklahoma. The flight home was a highlight: He had been upgraded to first class and treated as a hero. But he couldn't relax, couldn't shake the need to be ever vigilant. "I had to sit in the right passenger seat," he says. "I had to look for IEDs, something out of place. I'd look out the window. Like a dog's stare." The Speakes family knew Grant needed treatment, but he feared the stigma that often surrounds those who seek mental health counseling. At home in Washington, Grant Speakes couldn't relax and he startled easily, his father says. "The mood change was obvious," Stephen Speakes says. "In the case of Grant, he was the life of every party. ... He came back somber, dark, morose, depressed and occasionally angry." Grant Speakes knew he needed counseling but says he was reluctant to seek it from the Army because another soldier might need it more. "I also worried about the cloud it would put on my dad's career, my brother's and my own," he says. "It was something I wanted to talk about, but I couldn't. Because of that, it was hurting my relationship with Christy." The family found a private psychiatrist, and Speakes began counseling and treatment. 'More at peace' Treatment and time helped heal Speakes and allowed him to stay in the Army. He deployed to Iraq again in 2008 and returned home June 1, 2009, "more at peace," he says. Stephen Speakes, who retired in the fall from a top Army budget position, says Army leaders recognize the toll combat takes on soldiers. He says what happened to his son in Iraq has left permanent scars. Grant Speakes acknowledges that he's changed, in some ways for the better. He's at Fort Benning, Ga., honing his skills as an officer. He's not certain when he will deploy again. "There is life after PTSD," Speakes says. "I'm a survivor. I'm not holed up in a room with an M-4. 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