"Positive social supports can help promote resiliency even in the context of maltreatment and a genetic predisposition for psychiatric illness," she said.

Countless instances of child maltreatment occur each year, including nearly 1 million substantiated reports, and many other cases that are never brought to the attention of some authority. Although not all abused children are doomed to experience some type of psychiatric problem, depression is among the most commonly reported mental conditions among this group.

Also, genes can be a factor. Previous research in adults has shown that having a short version of the serotonin transporter gene, may increase susceptibility to depression after some stressful event. Among infants reared in stressful environments, those with the genetic variant show increased emotional distress, studies show.

Researchers have also found that the availability of a caring, stable parent or guardian may positively influence the long-term development of a person with a history of abuse.

In the current study, Kaufman and her team looked at 57 children who were removed from their homes due to allegations of abuse and/or neglect and a comparison group of 44 children with no history of maltreatment. The 5- to 15-year-old black, white, Hispanic and biracial study participants were from 67 families.

As in adult studies, children who had a history of significant stress -- maltreatment in this case -- and were genetically predisposed, seemed to be more vulnerable to depression than their peers, the researchers report in this week's Proceedings of the National Academy of Sciences (news - web sites).

Those from more stable homes, on the other hand, tended to have less signs of depression, regardless of whether or not they were genetically predisposed to the condition, the researchers note.

For example, among those genetically vulnerable to depression, maltreated children with low social support -- i.e. they did not always have someone to rely on when in need, talk to about personal things, share good news with, have fun with or go to for advice -- scored twice as high on a measure of the severity of their depression symptoms than did those with no history of abuse.

Frequent contact with a primary support person, such as a parent, relative, friend or other adult, was associated with lower depression scores.

In fact, among maltreated children with a slight genetic vulnerability to depression, those who were able to see their primary support only semiannually or less frequently had depression scores that were 33 percent higher than those with more frequent contact.

Altogether, these findings show that the risk for depression "may be modified by both genetic and environmental factors, with the quality and availability of social supports among the most important environmental factors in promoting resiliency even in the presence of a genotype expected to predispose to psychiatric disorder," Kaufman and her team write.