Veterans of the fighting in Iraq are more likely than other U.S. soldiers to suffer mild memory and attention lapses back home, but they also tend to have better reaction time, at least in the short-term, a study found.

The findings may simply reflect the normal changes that would be expected to occur as soldiers make the transition from combat to regular life.

But they could also signal more serious mental health problems down the road, said lead author Jennifer Vasterling, a psychologist and researcher with the Veterans Affairs' Southeast Louisiana Veterans Health Care System.

The study involved 654 soldiers who took mental-function tests a few months before going to Iraq in mid-to-late 2003 and within three months after returning in 2005. The researchers noted subtle changes in their scores.

If the changes persist, "that's where you have to worry about people developing stress-related emotional problems like post-traumatic stress disorder," Vasterling said.

The study appears in Wednesday's Journal of the American Medical Association. It is one of the first studies to show war's effect on military personnel by documenting before-and-after mental function.

Vasterling said the researchers hope their work will help "avoid some of the ambiguity and confusion that happened after the 1991 Gulf War," when it was unclear if some soldiers' ills were war-related.

While some of the changes documented in the study could be "considered as essentially normal coping experiences," it will be important to track the participants to see if they develop more serious problems, two British specialists in military psychiatry, Matthew Hotopf and Simon Wessely, said in an editorial.

A Pentagon study in JAMA earlier this year found that 35 percent of Iraq vets received psychological counseling shortly after returning, and earlier research found that about 17 percent of soldiers returning from Iraq had symptoms of post-traumatic stress.

About 11 percent of the vets Vasterling studied reported such symptoms upon their return, she said.

Most Iraq vets in Vasterling's study had some type of combat-related experience. Their before-and-after scores were compared with those of a group of 307 soldiers who were not sent to Iraq and who took the tests around the same time.

The psychological tests given are commonly used to measure thinking and motor skills. Most soldiers in both groups scored within a normal range on all the tests.

In one test measuring visual memory, participants looked at geometric designs consisting of squares and dots for 10 seconds and had to draw the pattern right away and then half an hour later.

Both groups' before-and-after scores declined slightly, but the declines were bigger among the Iraq veterans. The portion of Iraq veterans scoring in the bottom quarter on that test increased from 25 percent before Iraq to about 35 percent afterward.

In an attention-measuring test, a series of alphabet letters flashed briefly on a computer screen. For about eight minutes, participants had to watch for a specific letter and press the keyboard space bar or mouse each time it appeared.

It is the kind of test in which better scores are expected the second time around because the first time gave test-takers practice. But only about 1 percent of Iraq veterans who had scored in the bottom range the first time did better than that the second time, compared with 8 percent in the non-deployed group.

In a reaction-time test, participants were supposed to press the space bar or click a mouse as fast as they could each time a snowflake-like image flashed on the screen. Scores declined among the non-deployed but improved slightly among the Iraq vets.

The improvement makes sense, because war trains people to react quickly to life-or-death situations, Vasterling said.