Kids displaced by Hurricane Katrina responded to the stress of the natural disaster differently, with girls showing more signs of depression and boys becoming more withdrawn, a new study suggests.

While previous work has indicated differences between the sexes in response to stress, few studies have looked at the particular impact of natural disasters in which victims can experience trauma, loss and relocation.

"These folks experienced probably about as bad a hardship as a human being can in that they lost all their property, and also they lost all their social resources, they were forced to be displaced," said study researcher Jacob Vigil, of the University of New Mexico.

The results suggest psychological treatments designed to help disaster victims, who experienced Katrina five years ago this week, should account for gender, the researchers say.

"We can't expect boys and girls and men and women to react the same to these types of disasters," said David Geary, of the University of Missouri, also involved with the study.

In this case, girls might respond better to treatments that involve talking about their depression and anxiety — which is usually the treatment for both genders — while boys might benefit more from interventions that allow them to feel that they have regained their status in their community, Geary said.

"The follow-up treatments that are currently available are really probably better tailored for women and girls than for men and boys," Geary said.

Stress response

The study included 62 children ages 12 to 19 living in government relocation camps two months after Katrina hit. The children were surveyed to gauge their levels depression, anxiety, distress, aggression, and self-esteem.

The researchers also collected saliva samples to examine the children's biological response to stress. They tested the samples for levels of cortisol, a stress hormone, as well as alpha-amylase, an enzyme that indicates whether the body's "fight or flight" response to immediate stress has been triggered.

They compared the Katrina victim's psychological and biological response to stress to that of a control group of 53 adolescents from Missouri who were very similar to the Katrina group in terms of age, race and socioeconomic status. Both groups were over 93 percent African American, and over 67 percent had a history of government assistance, including welfare and food stamps.

Girls in both groups could be considered depressed, but those in the Katrina group had higher levels of depression.

Both genders in the Katrina group had lower levels of cortisol than those not hit by Katrina, an indicator of chronic stress. "Cortisol is very helpful in getting you focused and prepared, but if it goes on and on and on, the system kind of shuts down," Geary said.

There were no differences between the sexes in terms of how much alpha-amylase they produced.

Sex differences

Interestingly, although the biological responses appeared similar between the sexes, the resulting behaviors are different, Vigil said.

"Males and females have the same physical stress systems, but they seem to be specialized for producing different types of expressive behavior," he said.

These behavioral differences might be due to differences in the types of relationships males and females tend to form.

Females tend to have close intimate relationships and smaller social networks, Vigil said. Behaviors like depression "are very effective for increasing help from other people, but only from intimate confidants, the types of relationship partners that females form more so than males," he said.

In contrast, males tend to have larger social networks and form less intimate relationships in which dominance and aggression play big roles, Vigil said.

Guys also use aggressiveness to compete for status, Geary said. Previous work on primates has shown that when males lose contests for status, they "become behaviorally withdrawn and inhibited and less aggressive," he said. This is similar to the way the Katrina boys reacted with a decrease in aggression, he said.

The results were published in the July/August 2010 issue of the journal Child Development.