BOSTON — Members of the 883rd Medical Company treat the kinds of wounds that can't be seen but are sometimes just as damaging as physical injuries.

The "combat stress control" unit, which headed to Iraq Sept. 2 for a second deployment, offers counseling and advice to soldiers who may be suffering from anxiety, depression, insomnia and a host of other psychological problems associated with combat.

The unit, which spent three months in Iraq in 2003, includes psychiatrists, psychologists, social workers and other mental-health workers.

Staff Sgt. Robert Davis, 30, of Newton, a mental-health technician, said during his first deployment he saw many soldiers who had anxiety and trouble sleeping — conditions that were magnified by the mobile nature of the war.

He said the unit also offered counseling to members of a squad that had watched as their leader was killed by anti-aircraft gunfire.

"They were trying to cope not only with losing a leader and a friend, but they had also witnessed his death in a rather horrific way," Davis said.

Col. John Cooper, who runs an inpatient unit at a psychiatric hospital and teaches at Harvard Medical School, said he saw a variety of reactions to "really gruesome and horrible things" during the unit's first Iraq deployment.

"I think really the big thing was just the uncertainty of how long they were going to be there," Cooper said.

An Army report released in July found that psychological stress is weighing particularly heavily on National Guard and Reserve troops in Iraq.

The Army sent a team of mental-health specialists to Iraq and Kuwait last summer to assess conditions and measure progress in implementing programs designed to fix mental-health problems discovered during a similar survey of troops a year earlier.

The initial inquiry was triggered in part by an unusual surge in suicides among soldiers in Iraq in July 2003.

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

However, it found that 13 percent of soldiers had mental-health problems, most suffering from acute or posttraumatic stress.

The issue has received renewed attention since Marine Sgt. Daniel Cotnoir was charged with shooting into a crowd in Massachusetts last month, injuring two people.

Cotnoir's lawyer has said he was receiving psychological counseling after serving eight months in Iraq. A mortician by trade, he retrieved the bodies of dead U.S. soldiers.

Two people were treated for minor injuries after the shooting.

The 883rd, which started as a malaria-control unit during World War II, is one of nine combat stress units the Army has sent to Iraq. The unit also served in Kuwait during the Persian Gulf War.

At the farewell ceremony Aug. 18, U.S. Rep. Martin Meehan, D-Mass., said he has drafted legislation that would require every returning serviceman to receive a thorough psychological examination along with a physical exam.

"The psychological wounds can be much more destructive," Meehan said.