Two months after returning from Iraq, some U.S. Army soldiers have displayed subtle signs of confusion, reduced attention span and impaired memory that suggest a slow readjustment to civilian life, according to a study published last Wednesday.

The study also found an increase in reaction speed and a heightened level of tension among the soldiers, said lead author Jennifer J. Vasterling, a psychologist with the Southeast Louisiana Veterans Health Care System.

The findings, published in the Journal of the American Medical Association, are consistent with "an adaptive response to a life-threatening situation," she said.

The psychological changes most likely were a result of the soldiers' constant hyper-vigilance in Iraq — a trait that is helpful in battle but counterproductive on their return.

"The brain can put only so much cognitive effort in a given direction," Vasterling said.

Psychologist Jennifer Peskind of the University of Washington, who was not involved in the study, agreed that the soldiers' hyper-vigilance was "a distracter" that impaired their ability to focus on mundane tasks of memory and reasoning. Overall, however, she characterized the soldiers' psychological changes as "mild."

The study, the first to examine psychological characteristics of soldiers both before and after deployment to the Middle East, found no significant incidence of post-traumatic stress disorder.

Earlier studies have shown that as many as one in every eight soldiers who saw duty in Iraq was diagnosed with PTSD within a year after their return and that as many as a third of them have sought psychiatric help.

But a study reported in March by Dr. Charles W. Hoge and his colleagues at the Walter Reed Army Institute of Medical Research found that 90 percent of those with PTSD showed no signs of the disorder in the first months immediately after their return.

Vasterling's group studied 654 soldiers who were examined both before and after their deployment, comparing them to a control group of 307 soldiers who were not deployed.

They found that about three out of 10 of the returning veterans reported some mental confusion, compared to two out of 10 before deployment. Similarly, three out of 10 had small problems in verbal learning skills, memory and maintaining attention. About one in four reported some depression.

Vasterling said she thinks the symptoms will mostly disappear over time and plans to re-evaluate the soldiers a year after their return.

"The body has learned how to respond to a life threat over an extended period of time," she said. "It's doubtful that it can be turned off like a light switch."