The Romanian study, which tracked children for 12 years, shows reach of social isolation.
Children who grow up in institutions instead of with families have major deficits in brain development, said a study of Romanian orphans.
The findings, published online in the Proceedings of the National Academy of Sciences, underscore the importance of an enriched environment during infancy and childhood and may help explain the increased rates of depression and anxiety disorders known to exist among institutionalized children.
The report comes from the Bucharest Early Intervention Project, which has been following 136 Romanian orphans for 12 years, since the children were infants. It is the first study to randomly assign children either to foster care or to the institutional care of orphanages.
Such randomization -- ethically possible because all the children would otherwise have remained in institutions -- has allowed the scientists to ensure that other factors, such as physical appearance or personality, did not affect whether children were chosen to join a family or remained in an institution.
Striking find revealed in MRIs
Researchers at Harvard University, the University of Maryland and Tulane University worked with authorities to place half the children with foster families. Children living with their biological families have served as a control group.
The team has published almost 50 research papers since the project began, showing that the orphans who remained in institutions have significantly more behavioral and neurological deficits than those who went to families: At age 4 1/2, more than 40 percent had anxiety disorders and 4 percent had major depressive disorders. Many also exhibited signs of autism.
In the new study, the team scanned the brains of 74 of the children, ages 8 to 11, using magnetic resonance imaging. What they found was striking: Brains of children in institutions had less white matter -- the type of tissue that connects different regions of the brain -- than orphans who were placed in foster care or children living with their own families. Reductions in white matter have been found in numerous neurological and psychiatric conditions, including autism, schizophrenia and attention deficit hyperactivity disorder, or ADHD.
'A 40-watt light bulb'
Senior author Charles Nelson, a developmental neuroscientist at Children's Hospital Boston, said the changes were likely related to a difference that the scientists had noticed earlier: Children in institutions had less electrical activity in their brains -- specifically, a kind known as "alpha power" -- than those who had gone to foster homes. "If a normal kid is like a 100-watt light bulb, these kids were a 40-watt light bulb," he said.
The observed brain differences seem to parallel some of the behavioral differences seen in the different groups of children -- notably, higher rates of depression and anxiety disorders in kids who remained in institutions, he said.
But the placements -- the children went to families when they were 6 to 31 months old -- did not erase all problems. Though the children with families were doing better than the children in institutions, brains of both groups remained far from normal, Nelson said, with less gray matter than children who had been with families all along.
Perhaps, Nelson said, the children were placed in homes too late; deprivations they experienced before that time were profound. Children in the orphanages are often left in rooms by themselves for hours at a time. He said the findings underscored both the potential for recovery from early-life isolation and the devastating reach social deprivation can have even if experienced only for the first few years of life.