PHILADELPHIA -- For children in foster care, living in a stable home has a beneficial effect, independently of their behavior problems when they start foster care.

Children who enter foster care with many behavior problems are less likely to have problems only 18 months later, if they are placed in a stable home. Conversely, among children who begin foster care with fewer apparent behavior problems, those who are moved more frequently are more likely to have subsequent problems than children in more stable placements.

The researchers analyzed data from the National Survey of Child and Adolescent Well-Being, a nationally representative study of children who were referred to child welfare agencies for maltreatment in 1999 and 2000. From a sample of 729 children who entered continuous foster care, the study team compared the child's behavioral well-being at baseline with outcomes after 18 months of out-of-home care. The children ranged in age from infancy to 15 years old.

After 18 months in foster care, half of the children studied were "early stabilizers," experiencing a long-lasting home placement within 45 days of entering the foster care system. Another 19 percent of the children received a long-lasting placement later than 45 days, while 28 percent did not achieve a long-lasting placement.

In the group predicted to be at low risk of instability, early stabilizers had a 22 percent risk of behavioral problems, compared to a 36 percent risk of behavioral problems among children in unstable placements. The different rates, said the study team, revealed that unstable placement increased the risk of behavior problems by 63 percent, even in children with fewer problems to begin with.

Among children in the high-risk group, where behavioral problems after 18 months were higher for everyone, instability still had a large effect. High- risk children with early stability had a 47 percent risk of behavior problems, compared to a 64 percent risk in high-risk children with unstable placements - amounting to a 36 percent increase in the risk of behavior problems due to instability.