Children who lack the direct care of their biological parents for extended periods show larger gray matter volumes in the emotional circuitry of their brains, according to a new Chinese study. Though these findings are preliminary, they suggest direct parental care influences brain development, say the researchers.

“Since the larger gray matter volume may reflect insufficient pruning and maturity of the brain, the negative correlation between the gray matter volume and IQ scores suggests that growing without parental care may delay the development of brain,” wrote the researchers in the study they presented at the annual meeting of the Radiological Society of North America.

However, biological parenting does not account for all the differences between groups of children.

"Children who had been adopted or placed in foster care showed a smaller deficit than orphans," Yuan Xiao, a doctoral candidate at Sichuan University told Medical Daily.

A New Culture of Migrant Work

In China, the economic boom has inspired hundreds of millions of laborers to relocate for months, even years at a time, to better jobs in cities far from their children, the researchers explain. This massive parental migration has resulted in millions of so-called “left behind children.” Though cared for by relatives, these children lack direct parental care from their biological parents for long periods. How does such an experience impact the brain?

To explore this circumstance, Dr. Su Lui, senior investigator and a professor at Sichuan University, and his colleagues worked with 38 LBC who had lived with the absence of both biological parents for more than six months. The children, 21 boys, were between the ages of 7 and 13, with an average age of 9.6. The researchers enlisted the help of 30 comparison children, 19 boys, between the ages of 7 and 14 and all living with their parents.

After measuring each child’s IQ, the team performed MRI brain scans to view gray matter volume and compared the data between groups.

The brains of the left-behind children boasted larger gray matter volumes in multiple brain regions, especially in emotional brain circuitry, compared to the children living with their parents, the researchers discovered. Overall, the IQ scores of the left-behind children was not significantly different from those of the other children. Still, the gray matter volume in a brain region associated with memory encoding and retrieval was negatively related to IQ score.

"I acknowledge that left-behind children (LBC), orphans and adopted children may have something in common, such as early adversity as well as stress. But, these left-behind children are quite different from the orphans or adopted children," said Xiao. "First, they have no history of institutional rearing, or have not experienced the extreme deprivation. Second, left-behind children are mostly taken care of by the grandparents."

Though grandparents usually provide food and clothing, Xiao explained, they often have fewer years of education than parents and "they often have less time and energy to attend to the psychological and emotional well-being of the children than the LBC might typically receive from attentive parents."

Ultimately, the researchers believe the negative correlation between gray matter volumes (a possible reflection of insufficient pruning) and IQ scores indicates direct parental care — or its lack — alters the trajectory of a child's brain development. Based on this finding, Lui, Xiao and their colleagues call for public health efforts to provide early interventions for the millions of children currently left behind by their parents.

Source: Xiao Y, Yang L, Yan Z, Fu Y, Du M, Lui S. Increased Gray Matter Volume of Emotional Circuits in Children without Direct Parental Care. RSNA Annual Meeting. 2015.

Note: Comments from Yuan Xiao were added to this article after initial publication.