The survey of 1,000 troops found problems including anxiety, depression, nightmares, anger and an inability to concentrate, said Lt. Gen. Kevin Kiley and other military medical officials. A smaller number of troops, often with more severe symptoms, were diagnosed with post-traumatic stress disorder, or PTSD, a serious mental illness.

The 30 percent figure is in contrast to the 3 percent to 5 percent diagnosed with a significant mental health issues immediately after they leave the war theater, according to Col. Elspeth Ritchie, a military psychiatrist on Kiley's staff. A study of troops who were still in the combat zone in 2004 found 13 percent experienced significant mental health problems.

Soldiers departing a war zone are typically given a health evaluation as they leave combat, but the Army is only now instituting a program for follow-up screenings three to six months later, said Kiley, speaking to reporters at a breakfast meeting.

Screenings of 1,000 U.S. soldiers who returned from Iraq to their home bases in Italy last year found that three to four months later, 30 percent of them had some mental health difficulties — a much greater incidence than expected. Kiley attributed that to post-combat stress problems taking time to develop once the danger has passed.

Only about 4 percent or 5 percent of troops coming home from combat actually have PTSD, but many others face problems adjusting when they come home, Kiley said.

Such problems are sometimes more acute in members of the National Guard, who return to a civilian job when they leave active military duty, Ritchie said.

Military medical officials, however, cautioned against people reading their data as suggesting the war had driven so many soldiers over the edge. Instead, they characterized the anxiety and stress as normal reactions to combat, seeing dead and mutilated bodies, and feeling helpless to stop a violent situation.

Still, such reactions can lead to problems with spouses and children, substance abuse and just day-to-day life, they said.

Truck drivers and convoy guards in Iraq are developing mental health problems in greater numbers than other troops, Ritchie said, suggesting the long hours on the road, constantly under threat of attack, are taking their toll.

The military has about 200 mental health experts in Iraq, grouped in what the Army calls "combat stress control teams." These teams are at many posts around the country and talk with troops after battles, try to prevent suicides and diagnose troops who should be evacuated from of the country because of mental health problems.

"They are worth their weight in gold," Kiley said of the teams.

An inquiry into the mental health of soldiers serving in Iraq found an improvement in the mental health and morale in 2004 over 2003. The military made its report on the inquiry public last week.

The report said the number of suicides in Iraq and Kuwait declined from 24 in 2003 to nine last year.

Historically, mental health problems have always been a part of warfare, and was looked at systematically when shellshock cases accounted for significant losses during World War I.

Ritchie said mental health cases ebb and flow during a war, and suggested they are sometimes connected to a soldier's sense of success of the larger war effort. During the Korean War, cases increased when U.S. forces were losing ground but decreased as the situation improved, she said.