A mother's nurturing love for her preschooler fosters the growth of a region in the child's brain that is key to learning and responding to stress, researchers have found.
Until now, there's been no solid proof linking a supportive, attentive parent to changes in the brain anatomy of children. Many studies have shown the importance of nurturing early in life in rodents and primates.
The brain's hippocampus is important for learning, memory and coping with stress.
In this week's online edition of the Proceedings of the National Academy of Sciences, U.S. researchers reported that some children had a hippocampus almost 10 per cent larger than their peers whose mothers who didn't show as much care. The findings only applied to children without depression.
"I think the public health implications suggest that we should pay more attention to parents' nurturing, and we should do what we can as a society to foster these skills because clearly nurturing has a very, very big impact on later development," said study author Dr. Joan Luby of Washington University's medical school in St. Louis.
In the study, researchers used MRI to measure the hippocampus of 92 children from St. Louis who started participating in the research project as preschoolers.
First, as preschoolers, the children were closely watched as they interacted with a parent, usually mom, as she filled out a survey. At the same time, the children had to wait for eight minutes before opening a brightly wrapped gift that was within arm's reach.
During the "waiting task," investigators took note of what supportive strategies the parent used to help their son or daughter wait patiently instead of acting on the impulse to tear open the gift immediately. Psychiatrists who didn't know anything about the subjects counted each display of support by the caregiver.
A supportive mother might console the child and explain there were only a few more minutes to wait.
The kids and their parents were assessed four to six times over the course of the study. When the children reached ages seven to 13, they had the MRIs to measure their brains.
Maternal support was "strongly predictive" of the size of the hippocampus at school age, the researchers said.
The children with low maternal support showed hippocampal volumes that were 9.2 per cent smaller, the study's authors found.
"We believe these findings have potentially profound public health implications and suggest that greater public health emphasis on early parenting could be a very fruitful social investment," the study's authors concluded.
"This finding, when replicated, would strongly suggest enhancement of public policies and programs that provide support and parenting education to caregivers early in development."
Factors such as use of medications, traumatic life events and a mother's history of depression were taken into account.
While nearly 97 per cent of the caregivers in the study were mothers, the researchers said they expect the effect would apply to the primary caregiver, whether that's mom, dad, a grandparent or someone else.
The study was funded by the U.S. National Institute of Mental Health.