Our brains make us who we are. But what makes our brains? Which of the myriad experiences and characteristics that define a child's life and identity — from screen time to sleep to illness — leave imprints in the folds of that child's brain?
After analyzing hundreds of biological, psychological, social and environmental factors related to children's development, researchers at Washington University School of Medicine in St. Louis found that a family's financial situation and the resources and opportunities in a child's neighborhood had the strongest connection to brain development.
Socioeconomic factors accounted for about 16% of the variability in measures of children's brain function — far more than IQ, parenting style and health history.
The findings appear June 11 in Science.
"We set out to compare hundreds of influences on the developing brain on a level playing field, and for the first time at this scale, we showed that socioeconomic conditions leave the deepest imprint of any factor we looked at," said senior author Nico U. Dosenbach, MD, PhD , the David M. and Tracy S. Holtzman Professor of Neurology at WashU Medicine. And the socioeconomic signal seems to travel through everyday burdens like poor sleep and chronic stress.
As part of the study, the researchers analyzed brain scans from nearly 12,000 children ages 9 to 10 to see how a child's environment, health and regular activities are related to brain development. Of hundreds of factors examined, the team found that the socioeconomic status of a child's family had the strongest relationship with that child's brain structure and function. Further, the parts of the brain that reflect socioeconomic factors were the same areas most sensitive to sleep and stress, suggesting that socioeconomic disadvantage affects the brain indirectly through disrupted sleep and chronic stress.
"The brain of a child from a low socioeconomic background looks like that of a child from a high socioeconomic environment that has been sleep-deprived and stressed," said Dosenbach. "It's not a less-smart brain. It appears to be a tired and stressed brain. The good thing is that sleep and stress are both modifiable. If we can find a way to improve sleep and reduce stress for children from households with more limited socioeconomic opportunities, we may be able to reduce brain differences linked to socioeconomics."
Mapping the factors associated with brain structure and function
For years, researchers have tried to figure out the link between physiological brain features and people's IQ, mental health or specific behaviors using "brain-wide association studies." Such studies use magnetic resonance imaging (MRI) scans to map a person's brain structure and function to specific cognitive, behavioral or other traits. But the studies have largely ignored the potential impact of children's environments and experiences on brain development.
In light of research showing childhood poverty, chronic stress and other adverse experiences affect brain development and mental and physical health, Dosenbach and colleagues aimed to expand brain-wide association studies. They broadened their map to include 649 variables divided into 12 categories:
- socioeconomics
- screen time
- cognitive abilities, such as test scores and memory
- demographics, including race and sex
- culture and environment, such as religion, language and exposure to noise or pollution
- physical health
- mental health
- social adjustment, such as friendships and bullying
- substance use, including use of or exposure to people using illicit drugs and alcohol
- parenting
- personality, including factors such as extraversion and self-control
- medical history
Then, they set out to answer two questions: How are those variables reflected in the way the brain functions or is structured? And further, are relationships between IQ scores and brain physiology genuine or entangled with other variables?
To tackle these questions, the team analyzed data from 11,878 children who are participating in the NIH-funded Adolescent Brain Cognitive Development Study, a long-term, nationwide study of brain development and child health, including a site based at WashU Medicine. Using MRI scans of the children, they performed sophisticated analyses to assess the links between each variable and both brain structure — as measured by the thickness of the cortex, the crumpled outer layer of the brain — and function, as indicated by the strength of connections between key functional networks in the brain.
Of the top 40 variables linked to brain function, 37 were socioeconomic, and of the top 40 tied to structure, 35 were socioeconomic. These included the social and economic resources in the child's neighborhood, akin to the overall wealth of an area. Strong influences included family income, homeownership and poverty rates, and access to transportation. The remaining top variables were related to sleep, screen time and stress.
"I started calling it the 'elephant in the brain,'" said first author Scott Marek, PhD , an assistant professor in the WashU Medicine Mallinckrodt Institute of Radiology. "I thought socioeconomic opportunity would matter, but I didn't think it would matter this much. It just dwarfed everything else."
Socioeconomic variables were strongly associated with functional features in the motor and sensory areas of the brain, which are highly sensitive to day-to-day variation in sleep and stress. Brain regions associated with cognition and problem-solving were less tied to socioeconomic factors, indicating that socioeconomic conditions seem to shape children's brains mainly by altering systems tied to bodily sensations and movement rather than directly changing "thinking" regions. As a result, what might look like a brain difference in cognitive ability is more likely a reflection of differences in everyday burdens such as fatigue and chronic stress than a difference in intellectual capacity.
The relationships between socioeconomic variables and the brain were not linked to demographic factors such as sex and race.
Brain imaging reveals no signature of IQ scores
For decades, scientists have searched for hallmarks of intelligence in the brain's contours and composition and have come up with mixed results. Dosenbach and Marek might have uncovered why: earlier work that found associations between IQ and physical brain features such as cortical thickness could have been mistakenly picking up on socioeconomic factors instead. Research from the social sciences has shown that IQ scores rise with social privilege, for example.
To understand how socioeconomic factors affect the relationship between IQ and the brain, the researchers performed a statistical analysis that accounted for socioeconomic influence as an aggregate and then looked at the association between IQ and various brain areas and networks. Adjusting for socioeconomic status greatly diminished the associations between brain measures and IQ scores to the point where roughly 70% of these associations were no longer statistically significant.
In another analysis, Marek and Dosenbach took socioeconomic factors out of the equation by analyzing only children from high socioeconomic backgrounds. In this group, IQ had no correlation with brain structure or function.
"If we look at children's brain scans, we can tell how well off their family is and how much sleep and screen time they get, but we can't tell their IQ, at least not after adjusting for socioeconomic opportunity," said Marek. "That tells me IQ is not rooted in neurobiology. The environment shapes children's brains in ways that have been misinterpreted as being reflections of IQ, when really they're just reflections of stress and sleep deprivation. Those are things we can do something about to improve kids' brain health."
Marek S, Donohue MR, Karcher NR, Hoyniak C, Chauvin RJ, Meyer AC, Miller J, Van AN, Wang A, Baden NJ, Suljic V, Scheidter KM, Monk J, Whiting FI, Ramirez-Perez NJ, Krimmel SR, Metoki A, Paul SE, Gorelik AJ, Hendrickson TJ, Malone SM, Schwarzlose RF, Cardenas-Iniguez C, Herting MM, Petersen SE, Luby J, Randolph AC, Shanahan MJ, Turkheimer E, Kay BP, Gordon EM, Laumann TO, Barch DM, Fair DA, Tervo-Clemmens B, Dosenbach NUF. Patterns of brain-wide associations reflect socioeconomics. Science. June 11, 2026. DOI: 10.1126/science.aee6213
This research was supported in part by the National Institutes of Health (R00MH121518, K23MH125023, R01MH139880, R00HD109454, P30ES007048, U24ES036819, R25DA059073, R25DA061824, R01ES032295, R01ES031074, K23NS123345, U01DA041120, K23DA057486, K23DA057486, U1DA041120), National Science Foundation (DGE-213989), Jacobs Foundation, and Kiwanis Foundation.
A.N.V., D.A.F. and N.U.F.D. have a financial interest in Turing Medical Inc. and may financially benefit if the company is successful in marketing FIRMM motion monitoring software products. D.A.F., A.N.V., N.U.F.D. may receive royalty income based on FIRMM technology developed at the University of Minnesota and Washington University and license. Turing Medical Inc. D.A.F. and N.U.F.D. are co-founders of Turing Medical Inc.
About WashU Medicine
WashU Medicine is a global leader in academic medicine, including biomedical research, patient care and educational programs with 3,100 faculty. Its National Institutes of Health (NIH) research funding portfolio is the second largest among U.S. medical schools and has grown 78% since 2016. Together with institutional investment, WashU Medicine commits over $1.6 billion annually to basic and clinical research innovation and training. Its faculty practice is consistently among the top five in the country, with more than 2,550 faculty physicians practicing at 200 locations. WashU Medicine physicians exclusively staff Barnes-Jewish and St. Louis Children's hospitals — the academic hospitals of BJC HealthCare — and Siteman Cancer Center , a partnership between BJC HealthCare and WashU Medicine and the only National Cancer Institute-designated comprehensive cancer center in Missouri and southern Illinois. WashU Medicine physicians also treat patients at BJC's community hospitals in our region. With a storied history in MD/PhD training, WashU Medicine recently dedicated $100 million to scholarships and curriculum renewal for its medical students, and is home to top-notch training programs in every medical subspecialty as well as physical therapy, occupational therapy, and audiology and communications sciences.
