It could be new evidence of the kind of stress that's placed on military families when a family member is deployed overseas.
Researchers have found that preschoolers who have a parent away at war are more likely to show aggression than other young children in military families.
It's the first published research on how the very young react to wartime deployment.
The study was a small one, focusing on fewer than 200 children. The researchers looked at families living on a large Marine base in 2007. They found that children between the ages of 3 and 5 who had a deployed parent scored an average of five points higher for behavioral problems on two questionnaires that are widely used in child psychology.
They also found that about 1 in 5 of the older preschoolers with a parent at war displayed troubling emotional or behavioral signs.