February 1, 2012 — Early maternal support and nurturing has a strong positive effect on brain development in young children, new research shows.

In a longitudinal study, researchers found that supportive caregiving during the preschool years predicted larger hippocampal volume at school age in nondepressed children.

"This particular publication is unique in that it combines observational data of parent-child interaction at preschool with structural brain outcomes at school age," Joan Luby, MD, professor of child psychiatry and director of the Early Emotional Development Program at Washington University School of Medicine in St. Louis, who led the study, told Medscape Medical News.

Dr. Joan Luby

"It's the first finding in humans of a clear link between early nurturance and hippocampal volume. A well-established link has been known in animals for more than 20 years," Dr. Luby added. "This has very important general public health implications about the importance of attention to early parenting."

The study was published online January 30 in Proceedings of the National Academy of Sciences (PNAS).

Unique Focus

Commenting on the study for Medscape Medical News, Charles A. Nelson III, PhD, professor of pediatrics and neuroscience from Harvard Medical School in Boston, Massachusetts, said "a unique element of this study is that it focuses on positive outcomes rather than negative."

"There is an abundance of work showing reductions in hippocampal volume when children, or even adults, experience adversity," explained Dr. Nelson, who was not involved in the study. "This turns that issue on its head and shows that hippocampal volume actually increases as a function of increases in maternal warmth."

The 92 children in the study were originally recruited between the ages of 3 and 6 years from daycare centers and preschools in the St. Louis, Missouri, metropolitan area. The sample included 51 healthy nondepressed children and 41 with early-onset depression.

Between the ages of 4 and 7 years, the children were closely observed and videotaped interacting with a parent, almost always a mother, during a challenging and mildly stressful task.

How much or how little the parent was able to support and nurture the child in this stressful situation, which was designed to approximate the stresses of daily parenting, was evaluated by raters blind to the child's health or the parent's temperament.

"Whether a parent was considered a nurturer was not based on that parent's own self-assessment. Rather, it was based on their behavior and the extent to which they nurtured their child under these challenging conditions. It was very objective," said Dr. Luby.

Magnetic resonance imaging (MRI) scans of the brain obtained at school age revealed that children without depression who had very nurturing mothers in preschool had a hippocampus almost 10% larger than their peers whose mothers were not as nurturing. The estimated increase in hippocampal volume by unit of increased maternal support was 13.4 mm3, the researchers report.

Robust Finding

Notably, say investigators, the link between healthy maternal nurturing and increased hippocampal volume remained robust even after accounting for other factors known to affect hippocampal volume, such as stressful life events, comorbid internalizing and externalizing symptoms, and a history of maternal depression.

Maternal nurturing did not have a strong impact on hippocampal volume in the children with early-onset depression.

"The fact that this association was only observed among the nondepressed children argues, and is consistent with, the fact that early-onset depression may limit a child's ability to benefit from warm, maternal care," Dr. Nelson said. "This is quite unfortunate."

Dr. Luby and colleagues think their findings could have "profound public health implications and suggest that greater public health emphasis on early parenting could be a very fruitful social investment."

"The finding that early parenting support, a modifiable psychosocial factor, is directly related to healthy development of a key brain region known to impact cognitive functioning and emotion regulation opens an exciting opportunity to impact the development of children in a powerful and positive fashion," they write.

"This finding, when replicated, would strongly suggest enhancement of public policies and programs that provide support and parenting education to caregivers early in development," they add.

The study, Dr. Nelson commented, has a "few limitations, but nothing serious, just the nature of research such as this." He noted that the investigators focus exclusively on the hippocampus and do not report on whether other structures benefit from increases in maternal care. They also do not address whether increases in hippocampal volume affect behavior; for example, do these children show improvements in learning and memory?

The study was supported by the National Institute of Mental Health. The authors and Dr. Nelson declare no conflicts of interest related to this work.

PNAS. Published online January 30, 2012. Article

