In the initial five years of a child’s life, over half of the calories they ingest are dedicated to the significant task of brain development. Constructing a brain, which involves forming neuronal connections that handle memories, language, perception, and motor control, is an energy-demanding process. The distinctive structure of a child’s brain, which determines their thoughts and emotions, is continuously molded by the interaction between their environment and genetic instructions within their growing tissues.
Researchers have long been curious about which childhood factors most significantly impact brain development. Recent access to extensive datasets has begun to provide answers. A study by researchers at Washington University School of Medicine, analyzing brain scans from nearly 12,000 children aged 9 and 10, identified socioeconomic status as the primary environmental factor affecting brain structure and function, surpassing IQ, parenting style, and health history.
The study, published in Science, indicates that household income, poverty rates, and neighborhood economic activity explain about 16% of the variation in children’s brain function. These disparities likely arise from chronic stress and poor sleep, common in less advantaged settings.
Scott Marek, a pediatric neuroimaging researcher and study co-leader, emphasized the importance of this epidemiological framework in directing resources and efforts to understand brain development mechanisms. “This data strongly suggests a connection to socioeconomic status, particularly related to sleep, stress, and potentially screen use, which are factors individuals can somewhat control,” Marek explained.
Experts acknowledged the study’s evidence that childhood environment plays a crucial role in brain organization. However, they cautioned against assuming that interventions targeting sleep or stress reduction would necessarily enhance brain development.
Janet Currie, a health economist at Yale University, raised a critical question: “If socioeconomic status in neighborhoods changes, will it lead to changes in brain development?” This inquiry needs answering before implementing interventions.
The study is a brain-wide association study (BWAS), utilizing statistical methods to correlate individual differences in living conditions or behaviors with brain structure and function variations within a large dataset. This analysis was part of the Adolescent Brain Cognitive Development (ABCD) Study, a longitudinal brain-imaging project funded by the National Institutes of Health, involving over 20 sites across the U.S.
Since 2017, ABCD has recruited children aged 9 and 10 for biennial neuroimaging over ten years. Participants also provide blood samples and undergo comprehensive behavioral assessments, including language, memory, and IQ tests.
Brain scans enable researchers to examine cortical thickness and resting-state activity—indicators of brain function—and to create connectivity maps showing communication patterns between brain regions. Marek and colleagues, collaborating with ABCD partners, explored links between these brain function metrics and 649 variables related to children’s lives, covering mental and physical health, parenting, friendships, substance use, noise or pollution exposure, cognitive abilities, screen time, and socioeconomic and cultural factors.
The analysis of data from 11,878 children identified 40 variables connected to brain function, 37 of which pertained to socioeconomic factors, including neighborhood wealth, family income, homeownership, and transportation access. Socioeconomic factors also dominated the top variables linked to brain structure, with sleep, screen time, and stress being the other significant variables.
Nico Dosenbach, a neurologist and study co-leader, noted that brain patterns linked to low socioeconomic status resemble those from sleep deprivation or stimulant use. Such patterns show heightened reactivity in brain areas related to sensory and motor functions, contrasting with those associated with higher-order cognition, involving the frontal cortex and executive functions.
“Initially, I was surprised,” Dosenbach admitted. However, the connection between sleep and stress as outcomes of low socioeconomic status soon became clear. Though the evidence is still circumstantial, it implies that socioeconomic status “encapsulates various factors altering the brain, with IQ merely accompanying these changes.”
Previous research connected IQ with physical brain attributes like cortical thickness. Dosenbach and Marek suspect these studies were inadvertently measuring socioeconomic influences. Adjusting for socioeconomic differences in their analysis, they found that associations between brain structures and IQ scores diminished significantly, with 70% no longer statistically significant. “These associations nearly vanish because they are so intertwined with socioeconomics,” Marek stated.
Marek and his team observed similar patterns when replicating their study using data from the U.K. Biobank, predominantly consisting of individuals with white British or Irish backgrounds. Within the ABCD Study, they determined that brain differences linked to socioeconomic factors were not related to participants’ genetic ancestry.
This research arrives at a pivotal moment for exposomics, a field investigating how physical and social environments impact health.
In line with the Make America Healthy Again initiative, Health and Human Services Secretary Robert F. Kennedy Jr. has advocated for increased research into environmental causes of chronic diseases, autism, and other neurodevelopmental disorders. Last year, the National Institutes of Health allocated $50 million to investigate autism’s environmental links. While Kennedy and the MAHA group have raised concerns about pesticides, ultra-processed foods, fluoride, and vaccines, stress and sleep deprivation’s health impacts, rooted in socioeconomic disadvantage, have received considerably less focus.
