The study, which showed increasing rates of mental health problems for troops on extended or multiple deployments, also said well over one-third of soldiers and marines believed that torture should be allowed to gain information that could save the lives of American troops, or knowledge about insurgents.
Of the 1,320 soldiers and 447 marines who took part, about 10 percent said they had mistreated civilians through physical violence or damage to personal property.
The study was conducted by Army medical experts from Aug. 28 to Oct. 3 last year.
“Soldiers with high levels of anger, who had experienced high levels of combat or who screened positive for mental health symptoms, were nearly twice as likely to mistreat noncombatants,” the acting Army surgeon general, Maj. Gen. Gale S. Pollock, told reporters.
The findings are posted at www .armymedicine.army.mil.
The survey data came out a month after Defense Secretary Robert M. Gates extended tours for soldiers in Iraq and Afghanistan to up to 15 months, from 12. American forces in Iraq are being increased under a security plan ordered by President Bush.
The report, the fourth prepared by the Army’s Mental Health Advisory Team since the war in Iraq began in 2003, showed that mental health problems like acute stress, anxiety and depression rose among troops facing longer deployments or their second or third tour in Iraq.
Over all, about 20 percent of soldiers and 15 percent of marines showed symptoms of anxiety, depression or acute stress. The rate was at 30 percent among troops with high combat experience.
Among soldiers, 27 percent of those with more than one tour of duty tested positive for a mental health problem, versus 17 percent for soldiers on their first deployment.
The rate of anxiety, depression and acute stress stood at 22 percent among soldiers deployed for more than six months and at 15 percent for troops in Iraq for less than six months. Army experts recommended that the Pentagon extend the interval between deployments to 18 to 36 months so that troops could recover mentally.
Mr. Gates said last month that troops in the region could expect to spend 12 months at home between deployments.
