The most powerful factors affecting a child's brain development involve socioeconomic opportunities, according to a study in the journal Science.

The analysis of more than 2,300 9- and 10-year-olds found that environmental factors ranging from household income to education to neighborhood quality are associated with brain differences that can clearly be seen in MRI scans.

The researchers also found that preteens who'd grown up in neighborhoods with lower incomes and limited social support had brain differences associated with less sleep and more stress.

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"Something is going on in these neighborhoods," says Scott Marek, the study's first author and an assistant professor of radiology at WashU School of Medicine. "We need to find out how socioeconomics is becoming biologically embedded."

The research "highlights the fact that the environment in which we grow up and live has powerful impacts on our brain," says Russell Poldrack, a psychology professor at Stanford University who was not involved in the study.

It also challenges earlier research that focused on links between brain development and factors like IQ and mental health.

Those factors do appear to have a small influence on brain development, says Dr. Nico Dosenbach, an author of the new study and a professor at WashU Medicine in St. Louis.

"But socioeconomics was, by a wide margin, absolutely the dominant variable," Dosenbach says.

As a result, some earlier studies linking cognitive performance to brain differences "may require reevaluation," says Dr. Theodore D. Satterthwaite, an associate professor at the University of Pennsylvania Perelman School of Medicine.

Those studies focused on factors like IQ or mental health without accounting for socioeconomics, says Satterthwaite, who co-authored a perspective piece that accompanied the new study. So a reevaluation including that variable could weaken or even negate the findings.

In fact, the new study adds to what Satterthwaite calls a "rising tide of research" over the past few years, suggesting that childhood environment has a powerful influence on brain development.

The goal of the new research was to take an unbiased look at brain development and consider every factor that might have an influence.

Data came from the federally funded Adolescent Brain Cognitive Development (ABCD) Study, which is tracking thousands of children starting at ages 9 and 10.

The researchers used brain scans from ABCD to identify differences in the organ's structure and communication networks. Then they looked to see whether those differences were associated with factors like a child's environment, cognitive abilities and mental health.

Finally, the team ranked each factor by how strongly it was associated with brain differences.

"The pattern that emerged was, at first, very confusing to us," Marek says.

Nearly all of the top-ranked factors were in some way related to socioeconomic opportunity. And these factors were associated primarily with brain differences in areas involved in sensory processing and motor control, not higher functions like attention or memory.

So the team worked to figure out how factors like income, preschool enrollment, healthcare access and neighborhood quality might be affecting brain development.

The apparent answer involves brain circuits involved in keeping someone awake and alert. These circuits are altered when children get less sleep, experience more stress, or spend a lot of time using social media.

The team found that all of those environmental factors are more prevalent in neighborhoods where children lack economic, educational and social opportunities.

The finding doesn't prove that these factors are actually causing the brain differences, Marek says, "But the data are screaming that we should be looking at sleep, stress and screens if we want to get somewhere."

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