A new study indicates that boys, but not girls, tend to suffer more from mental health problems including depression and conduct disorder after moving out of a poor neighborhood and into a better one.

Conduct disorder is characterized by acting-out behaviors like fighting, bullying, damaging property, cruelty to people or animals, cutting school and breaking other rules, according to the American Academy of Child and Adolescent Psychiatry.

"Giving poor families the opportunity to move to better neighborhoods has a significant mental effect on kids in the family," said lead researcher Ronald Kessler, a professor of health care policy at Harvard Medical School.

"The striking thing was the mental health effects were positive for girls and negative for boys," he added.

Kessler said that one reason for this difference might be the way in which boys and girls are seen by their new neighbors. He said that boys who come from a poor neighborhood to a better one are are automatically seen as "juvenile delinquents" and are treated differently.

"He doesn't get the same chance of integrating into the neighborhood," Kessler said. "Whereas, when a girl comes, 'She's this poor little thing from the inner city - let's help her.'"

While girls were found to do better in better neighborhoods, experiencing less violence and sexual assault, the level of violence didn't change for boys.

Kessler said the government should consider these types of problems when enacting and pursuing a public-housing policy.

"It's not just a roof over their head, but where that roof is," he said. "Every decision the housing authority makes is a simplistic herd decision, and it's going to hurt somebody in a meaningful way."

For their study, the researchers randomly chose around 4,600 families living in public housing in poor neighborhoods. Some families received vouchers to move to better areas, some received vouchers allowing them to move wherever they chose and some received no assistance.

At the beginning of the study, the children ranged in age from newborns to eight-years-old. Ten to 15 years later, the researchers interviewed around 1,400 boys and nearly 1,500 girls.

The team found that around seven percent of boys who moved from poor neighborhoods suffered major depression, compared with 3.5 percent of boys who remained in their poor neighborhoods. Differences were also significant for post-traumatic stress disorder, which showed a difference of 6.2 percent versus 1.9 percent, and conduct disorder, which showed a difference of 6.4 percent versus 2.1 percent.

6.5 percent of girls who moved had major depression, compared with 10.9 percent of those who stayed behind. 0.3 percent of girls who moved had conduct disorder, compared with 2.9 percent who didn't move.

Dr. Matthew Lorber, a child psychiatrist at the Lenox Hill Hospital in New York City, said the problem stems from a failure to identify and treat mental illness among at-risk poor children. He said that if these children had access to treatment, many of the problems they developed later on could be prevented.

The study was published March 5 in the Journal of the American Medical Association.