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New research provides one more reason to thank your mom this Mother’s Day.

In the first study of its kind, researchers at Washington University in St. Louis have found that preschool-age kids whose mothers actively support them during a stressful incident later show greater volume in the hippocampus, a region of the brain strongly associated with memory that has also been linked to the capacity to manage stress. The results, published in the Proceedings of the National Academy of Sciences, add to a growing body of research suggesting that nurturing parenting early in a child’s life is critical to their healthy development.

Previous studies have found that kids who receive warm, supportive parenting are better at coping with adversity and at completing cognitive tasks later in life. While studies in animals have found these benefits reflected in brain structure, prior neuroscience studies in humans zeroed in on at-risk kids, such as children raised in orphanages, which made the results difficult to generalize.

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In this new study, the researchers first recruited children between the ages of three and six, screening them for depression. When they were between the ages of four and seven, the children, along with their mothers, were observed in a stressful situation any parent would dread, known as the “waiting task”: The kids were asked to wait for eight minutes before opening a brightly wrapped gift sitting in front of them; the mothers, meanwhile, had to complete a survey. The researchers scored the parents based on the kinds of strategies—supportive or non-supportive—they used to help calm their anxious kids.

According to the study’s lead author, Jean Luby, a professor of child psychiatry at Washington University’s medical school, “supportive” parents provided reassurance to their child, offered their child a strategy for coping with their distress, showed affection (e.g., a pat on the back), and encouraged their child to wait patiently given that the reward would come soon, among other techniques.

When 92 of the children originally recruited for the study were between the ages of seven and 13, the researchers took scans of their brains, measuring the volume of their hippocampus.

The results show that mothers who were more supportive during the waiting task generally had kids whose hippocampi were bigger than those of the other kids years later. This was true even when the researchers controlled for factors known to affect the size of the hippocampus, such as whether a mother was depressed or a child had experienced traumatic events.

However, hippocampi were only significantly larger in children who weren’t diagnosed as depressed themselves. Depressed children had smaller hippocampi, even if their mothers acted supportive during the stressful task.

Prior research has linked hippocampus size to stress: A smaller hippocampus has been observed in people who’ve experienced a lot of stress, including people suffering from post-traumatic stress disorder. In this study, the fact that kids with nurturing mothers later had larger hippocampi suggests that the positive parenting techniques observed by the researchers may have profound effects on the kids, even down to the level of their brains, and may help make them more resilient to stress.

The researchers argue that because it’s possible to teach nurturing parenting practices, their results have profound implications that could positively affect the lives of countless children.

“Greater public health emphasis on early parenting could be a very fruitful social investment,” 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.”